Laser processing apparatus and method for adjusting the laser processing apparatus

Abstract

To provide a laser processing device, which can perform processing with a high quality, while making adjustment work shorter and simpler.SOLUTION: A laser processing device (1) comprises a laser oscillator (3), an irradiating part (45), a spatial light modulator (43) and a control part (5). The lase oscillator outputs a laser beam (B). The irradiating part is provided to direct the laser beam outputted from the laser oscillator towards a work-piece (W). The spatial light modulator is provided at a light path (BL) of a laser beam between the laser oscillator and the irradiating part. The control part is provided to control motion of the spatial light modulator, on the basis of a measured result of a wave-front of a laser beam measured by a wave-front measurer (47) that measures the wave-front. The irradiating part is configured to generate leaked light (BM) that is a portion of an incident laser beam and is not directed toward the work-piece. The wave-front measurer is provided so as to measure a wave-front of the leaked light.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laser processing apparatus configured to perform laser processing on a workpiece by irradiating the workpiece with a laser beam, and a method for adjusting such a laser processing apparatus.

Background Art

[0002] Laser processing using a high-energy laser beam is used in various applications such as laser slicing for generating wafers from semiconductor ingots and laser dicing for dividing wafers into individual chips. In this type of laser processing, when attempting to transmit the laser beam through a fiber, problems such as the fiber itself being thermally processed by the laser beam can occur. Therefore, a laser processing apparatus configured to spatially transmit the laser beam using optical elements such as mirrors and lenses is employed. However, in such a laser processing apparatus with spatial transmission, conventionally, there has been a problem that a great deal of labor and time are required to adjust the apparatus so that the irradiation state of the laser beam on the workpiece becomes a desired state. In this regard, Patent Document 1 discloses a technique for facilitating the adjustment of the laser optical axis.

Prior Art Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In this type of laser processing apparatus, it is required to enable high-quality processing while further shortening or simplifying the adjustment work. The present invention has been made in view of the circumstances exemplified above. [[ID= / / ]] ​​

[0005] The laser processing apparatus (1) is configured to perform laser processing on a workpiece (W) by irradiating the workpiece with a laser beam (B). The laser processing apparatus according to claim 1 is A laser oscillator (3) that outputs the aforementioned laser beam, An irradiation unit (405) is provided to direct the laser beam output from the laser oscillator toward the workpiece, A spatial light modulator (403) is provided in the optical path (BL) of the laser beam between the laser oscillator and the irradiation unit, A control unit (5) is provided to control the operation of the spatial light modulator based on the wavefront measurement results obtained by a wavefront meter (407) that measures the wavefront of the laser beam, Equipped with, The irradiation unit is configured to generate stray light (BM) which is a portion of the incident laser beam that does not go toward the workpiece. The wavefront meter is provided to measure the wavefront of the leaked light. , The control unit further monitors aging degradation based on the operating control state of the spatial light modulator and the wavefront measurement results from the wavefront meter. . Claim 6 The method described is a method for adjusting a laser processing apparatus (1) configured to perform laser processing on a workpiece (W) by irradiating the workpiece with a laser beam (B), The aforementioned laser processing apparatus is A laser oscillator (3) that outputs the aforementioned laser beam, An irradiation unit (405) is provided to direct the laser beam output from the laser oscillator toward the workpiece, A spatial light modulator (403) is provided in the optical path (BL) of the laser beam between the laser oscillator and the irradiation unit, Equipped with, The wavefront of a portion of the laser beam incident on the irradiation unit that is not directed toward the workpiece (BM) is measured by a wavefront meter (407). The operation of the spatial light modulator is controlled based on the wavefront measurement results from the wavefront meter. death, Based on the operating control state of the spatial light modulator and the wavefront measurement results from the wavefront meter, the deterioration over time is monitored. .

[0006] In addition, each element in the application documents may be denoted by a reference numeral in parentheses. However, such reference numerals merely indicate one example of the correspondence between the element and the specific configuration described in the embodiments below. Therefore, the present invention is not limited in any way by the notation of such reference numerals. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows a schematic configuration of a laser processing apparatus according to one embodiment of the present invention. [Figure 2] Figure 1 is a bar graph showing an example of the wavefront aberration analysis results using a wavefront meter. [Figure 3] Figure 1 is a bar graph showing another example of the wavefront aberration analysis results using a wavefront meter. [Figure 4] Figure 1 is a flowchart showing a specific example of an adjustment method for a laser processing device. [Figure 5] This is a conceptual diagram showing another specific example of the adjustment method for the laser processing apparatus shown in Figure 1. [Figure 6] This figure shows a schematic configuration of a laser processing apparatus according to another embodiment of the present invention. [Figure 7] Figure 6 is a flowchart showing a specific example of a method for adjusting a laser processing device. [Figure 8] This is a conceptual diagram illustrating the overview of a semiconductor wafer manufacturing method using a laser processing apparatus according to the present invention. [Figure 9] This is a conceptual diagram illustrating the overview of a semiconductor wafer manufacturing method using a laser processing apparatus according to the present invention. [Figure 10] This is a conceptual diagram illustrating the overview of a semiconductor wafer manufacturing method using a laser processing apparatus according to the present invention. [Modes for carrying out the invention]

[0008] (Embodiment) Hereinafter, embodiments of the present invention will be described based on the drawings. Note that for various modifications applicable to one embodiment, if they are inserted in the middle of the series of descriptions regarding that embodiment, it may prevent the understanding of that embodiment. For this reason, the modifications will not be inserted in the middle of the series of descriptions regarding that embodiment, but will be described collectively later. Also, the descriptions in each drawing and the descriptions regarding the device configuration, its functions, or operations described below corresponding thereto are schematic or simplified for the purpose of briefly explaining the content of the present invention, and the content of the present invention is not limited thereby. Needless to say, the descriptions in each drawing and the specific device configuration actually manufactured and sold do not necessarily match. That is, unless the applicant explicitly limits it during the application process of this application, it is needless to say that the present invention should not be construed restrictively by the descriptions in each drawing and the descriptions regarding the device configuration, its functions, or operations described below corresponding thereto.

[0009] (First Embodiment: Configuration) FIG. 1 shows a schematic configuration of a laser processing apparatus 1 according to an embodiment of the present invention. Note that FIG. 1 is a conceptual diagram for showing an outline of the configuration along the optical path BL of the laser beam B in the laser processing apparatus 1. For this reason, in FIG. 1, regarding the positional relationship in the drawing between each component, there is no particular technical meaning other than the positional relationship regarding the traveling order of the laser beam B in the optical path BL. That is, for example, the vertical direction in the drawing in FIG. 1 is not necessarily parallel to the direction of gravity action or the horizontal direction.

[0010] The laser processing apparatus 1 is configured to perform laser processing on the workpiece W by irradiating the workpiece W with the laser beam B. Specifically, as shown in FIG. 1, the laser processing apparatus 1 according to the present embodiment includes a processing stage 2, a laser oscillator 3, an optical system 4, and a control unit 5.

[0011] The processing stage 2 is configured to hold the workpiece W during laser processing. The laser oscillator 3, which may also be called a laser light source, is configured to output, i.e., emit, a laser beam B. The optical system 4 includes at least optical elements such as lenses and mirrors, and is configured to guide the laser beam B output from the laser oscillator 3 to the workpiece W. Note that "optical elements" may also be called "optical devices". The control unit 5 is provided to control the entire operation of the laser processing apparatus 1, including the relative movement between the workpiece W supported by the processing stage 2 and the laser beam B, and the output of the laser beam B in the laser oscillator 3. Specifically, the control unit 5 has a configuration as a so-called microcomputer, comprising at least a processor and memory, and is configured to perform various operations by reading and executing a program from the memory. "Memory" refers to non-transitional physical storage media such as ROM, magnetic disks, optical disks, and flash memory. At least one processor and at least one memory are provided.

[0012] The optical system 4 comprises an intermediate optical element section 401, a reflective mirror 402, a spatial light modulator 403, a first telescopic optical system 404, an illumination section 405, an objective lens 406, a wavefront meter 407, a second telescopic optical system 408, and a beam profiler 409. The intermediate optical element section 401 is located between the laser oscillator 3 and the reflective mirror 402 in the optical path BL of the laser beam B that travels from the laser oscillator 3 toward the workpiece W. The intermediate optical element section 401 comprises at least one optical element. Specifically, the intermediate optical element section 401 may be provided with, for example, a deformable mirror, an axicon lens, or a beam expander. The reflective mirror 402 is a so-called folding mirror and is provided to totally reflect the laser beam B that has passed through the intermediate optical element section 401 and direct it toward the spatial light modulator 403.

[0013] The spatial light modulator 403 is located in the optical path BL between the laser oscillator 3 and the irradiation unit 405, more specifically between the reflective mirror 402 and the first telescopic optical system 404. The spatial light modulator 403 is a reflective spatial light modulator having a plurality of pixels arranged in a two-dimensional array, and is configured to independently modulate the phase of the laser beam B for each pixel by displaying a hologram pattern on these pixels. Specifically, in this embodiment, the spatial light modulator 403 has a liquid crystal layer as the optical modulation layer, and is configured as a so-called LCOS-SLM. LCOS-SLM is an abbreviation for Liquid Crystal on Silicon-Spatial Light Modulator. The hologram pattern may also be called a CGH pattern or phase modulation pattern. CGH is an abbreviation for Computer-Generated Hologram.

[0014] The first telescope optical system 404 is positioned between the spatial light modulator 403 and the irradiation unit 405 in the optical path BL. The first telescope optical system 404 is configured to adjust the characteristics of the laser beam B transmitted between the spatial light modulator 403 and the irradiation unit 405 so that the laser beam B is incident at the pupil position of the objective lens 406 in a desired state. The irradiation unit 405 is provided to direct the laser beam B output from the laser oscillator 3 towards the workpiece W. Specifically, the irradiation unit 405 functions as a mirror that changes the direction of the laser beam B that has passed through the first telescope optical system 404 by reflection and directs it towards the workpiece W. The irradiation unit 405 is also configured to generate measurement light BM, which is a portion (for example, a few percent) of the incident laser beam B that does not go towards the workpiece W. In other words, in this embodiment, the irradiation unit 405 has the configuration of a so-called beam sampler. The objective lens 406 is positioned between the illumination unit 405 and the workpiece W in the optical path BL.

[0015] The wavefront meter 407 is provided to measure the wavefront of the measurement light BM, which is transmitted light generated in the irradiation unit 405. Specifically, the wavefront meter 407 has a configuration as a so-called Shack-Hartmann type wavefront sensor. The control unit 5 is provided to control the operation of the spatial light modulator 403 based on the wavefront measurement result from the wavefront meter 407. In this embodiment, the wavefront meter 407 is provided to be conjugate to the workpiece W. Specifically, a second telescopic optical system 408 is provided between the irradiation unit 405 and the wavefront meter 407. The design values ​​such as the focal length and spacing of a pair of lenses in the second telescopic optical system 408 are set so that the workpiece W and the wavefront meter 407 are conjugate to each other.

[0016] The beam profiler 409 is set up to monitor the beam shape and two-dimensional intensity distribution of the laser beam B. The beam shape and two-dimensional intensity distribution are hereinafter referred to as the "beam profile". "Setup" means positioning with high precision so that the beam profile of the laser beam B irradiated onto the workpiece W can be measured. Specifically, the beam profiler 409 is positioned with high precision at a specified position on a base (not shown) supporting the optical system 4, in the manner described in the prior application of Japanese Patent Publication No. 2022-167534. In this embodiment, the beam profiler 409 is provided in the path of the measurement light BM so as to measure the beam profile of the measurement light BM.

[0017] (First embodiment: effect) The effects achieved by the configuration of the laser processing apparatus 1, as described above, will be explained below, along with the adjustment method for the laser processing apparatus 1, with reference to the respective drawings.

[0018] First, the adjustment method for the laser processing apparatus 1 will be explained. Initially, each optical element constituting the optical system 4 is assembled to a specified position on a base (not shown). Next, the optical axis of the laser beam B is adjusted using a method as described in Japanese Patent Application Publication No. 2022-167534. The optical axis adjustment can be performed automatically under the control of the control unit 5 by supporting each optical element constituting the optical system 4 using an electrically adjustable stage (e.g., a piezo stage).

[0019] Here, the inventors discovered that the processing quality, such as processing accuracy, in the laser processing apparatus 1 is affected not only by the optical axis adjustment state but also by the wavefront state at the pupil position of the objective lens 406. Specifically, for example, if the optical axis is disturbed and the laser beam B does not properly incident on each optical element in the optical path BL, the wavefront will be greatly distorted. However, even if the optical axis is adjusted, aberrations may occur in each optical element. Therefore, for example, even if one of the multiple adjustment parameters in each optical element such as the intermediate optical element section 401 or the reflective mirror 402 is shifted by a small amount, while there may be almost no difference in the roundness of the laser beam B, a large difference may occur in the processing quality. However, even in such cases, a significant difference may occur in the wavefront measurement results.

[0020] Therefore, the control unit 5 controls the operation of the spatial light modulator 403 based on the wavefront measurement results using the wavefront meter 407. Specifically, the control unit 5 performs Zernike analysis on the wavefront map and calculates a correction hologram pattern that reduces each Zernike coefficient based on the results. Then, the control unit 5 displays the calculated correction hologram pattern on the optical modulation layer of the spatial light modulator 403. Figure 2 shows an example of the wavefront state of the laser beam B before correction by the correction hologram pattern. Figure 3 shows an example of the wavefront state of the laser beam B after correction by the correction hologram pattern. In Figures 2 and 3, the vertical axis shows the Zernike coefficients indicating wavefront aberration, and the horizontal axis shows the term number of the Zernike mode, i.e., the OSA / ANSI index. In other words, the control unit 5 controls the display of the correction hologram pattern in the spatial light modulator 403 so that the bar graph of the Zernike coefficients becomes "flat" as shown in Figure 3.

[0021] The flowchart in Figure 4 shows an example of the adjustment control operation of the laser beam B by the control unit 5 as described above. In the illustrated flowchart, "S" is an abbreviation for "step". The control unit 5 reads a program from memory and starts it up, and then sequentially executes the processes of steps 101 to 107 shown in the flowchart of Figure 4.

[0022] Specifically, in step 101, the control unit 5 displays a calibration pattern on the optical modulation layer of the spatial light modulator 403. The calibration pattern is a holographic pattern that allows the spatial light modulator 403 to perform a simple reflective function and is intended to compensate for the operational errors of the spatial light modulator 403. This calibration pattern is acquired prior to the adjustment control operation and is stored in memory in advance. In step 102, the control unit 5 measures the wavefront of the laser beam B while the calibration pattern is being displayed using the wavefront meter 407. This wavefront is the wavefront at a position conjugate to the processing position on the workpiece W (i.e., the pupil position of the objective lens 406). In step 103, the control unit 5 performs a Zernike transform on the wavefront measured in step 102 to obtain the Zernike coefficients for each term of the Zernike mode in the wavefront aberration of the laser beam B before aberration correction, as shown in Figure 2.

[0023] In step 104, the control unit 5 generates a correction hologram pattern to cancel out aberrations based on the acquired Zernike modes and displays it on the optical modulation layer of the spatial light modulator 403. Specifically, the control unit 5 generates a phase map corresponding to a Zernike mode in which the Zernike coefficient exceeds a predetermined threshold, and if there are multiple such phase maps, they are added together. Then, the control unit 5 generates a correction hologram pattern by inverting the phase map and folding the phase by 2π. Since the method for generating such a correction hologram pattern is already publicly known or widely known at the time of filing of this application, further detailed explanation is omitted in this specification.

[0024] In step 105, the control unit 5 measures the wavefront of the laser beam B while the corrected hologram pattern is being displayed using the wavefront meter 407. In step 106, the control unit 5 performs a Zernike transform on the wavefront measured in step 105 to obtain the Zernike coefficients for each term of the Zernike mode in the wavefront aberration of the laser beam B after aberration correction. In step 107, the control unit 5 determines whether the wavefront aberration of the laser beam B after aberration correction has reached the desired "flat" state as shown in Figure 3. This determination can also be made, for example, by determining whether the Strehl ratio is sufficiently high (i.e., above a predetermined threshold). If the correction is insufficient (i.e., step 107 = NO), the control unit 5 returns to step 104, generates and displays the corrected hologram pattern again, and then repeats the processes in steps 105 to 107. If the correction is sufficient (i.e., step 107 = YES), the control unit 5 terminates the adjustment control operation.

[0025] In this embodiment, the characteristics of the laser beam B are adjusted by monitoring the wavefront of the laser beam B and correcting it using the spatial light modulator 403. Therefore, the adjustment of the laser beam B can be performed without repeatedly performing experimental laser processing on the workpiece W or its dummy. Accordingly, according to this embodiment, it is possible to perform high-quality (e.g., high-precision) processing while further shortening or simplifying the adjustment work.

[0026] In this embodiment, the stray light from the laser beam B incident on the irradiation unit 405 is used as the measurement light BM, and its wavefront is measured by the wavefront meter 407. Therefore, the wavefront measurement is performed outside the optical path BL of the laser beam B directed toward the workpiece W. Thus, the wavefront meter 407 does not need to be removed from the laser processing device 1 even during actual laser processing of the workpiece W. Furthermore, the wavefront measurement can be performed in real time during actual laser processing of the workpiece W. Therefore, according to this embodiment, it is possible to effectively feedback control the wavefront state without stopping or shutting down the operation of the laser processing device 1.

[0027] There is a correlation between the correction hologram pattern in the spatial light modulator 403 and the wavefront information acquired by the wavefront meter 407. Therefore, it is possible to monitor the aging degradation of the laser processing apparatus 1 based on the difference between the two. In other words, the control unit 5 can monitor the aging degradation based on the operation control state of the spatial light modulator 403 and the wavefront measurement results from the wavefront meter 407. Based on these monitoring results, it is possible to correct the wavefront deviation due to aging degradation. However, the resolution of the hologram pattern and the wavefront information may differ. Therefore, considering the difference in resolution between the two, it may be possible to perform processing such as averaging or filtering on one or both. Furthermore, if the difference between the two becomes too large and it becomes difficult to achieve a good wavefront state by correction using the hologram pattern, it is possible to execute an abnormal notification such as a maintenance notification.

[0028] In this embodiment, the beam profile is also measured by the beam profiler 409 using the measurement light BM, which is stray light. Therefore, the beam profiler 409 does not need to be removed from the laser processing device 1 during the actual laser processing of the workpiece W, and the beam profile can be measured in real time during laser processing.

[0029] (Example of beam shaping using a spatial light modulator) As is well known, the spatial light modulator 403 can modulate the phase and intensity characteristics of the laser beam B in two dimensions. Therefore, by shaping the laser beam B using a hologram pattern and branching it into multiple beams, simultaneous multi-point processing of the workpiece W becomes possible. In other words, in this case, the laser processing apparatus 1 is configured to simultaneously irradiate the workpiece W with the laser beam B at multiple different positions in the in-plane direction intersecting the irradiation direction of the laser beam B. In this case, the control unit 5 generates a composite hologram pattern by combining a hologram pattern for branching, i.e., patterning, of the laser beam B and a correction hologram pattern for aberration correction, and displays it on the optical modulation layer of the spatial light modulator 403. In this case, the wavefront data used for the Zernike transform for generating the correction hologram pattern in step 105 above does not include the wavefront control component for shaping the laser beam B.

[0030] Figure 5 shows an example in which laser beam B is split into a total of four beam spots, from the first spot SP1 to the fourth spot SP4. In this example, the first spot SP1 to the fourth spot SP4 are assumed to be arranged in a rectangular shape. In the figure, the intensity of each spot is indicated by the darkness of the diagonal hatching. Furthermore, as shown in (a) of Figure 5, in this example, it is desirable that the first spot SP1 to the fourth spot SP4 have the same intensity.

[0031] Here, as shown in (b), we assume a situation where, in reality, the first spot SP1, the second spot SP2, and the fourth spot SP4 have almost the same intensity, while the intensity of the third spot SP3 is lower than these. In such a case, the control unit 5 can detect that this situation has occurred from the measurement results of the beam profiler 409. Then, as shown in (c), the control unit 5 generates a hologram pattern that increases the intensity of the third spot SP3. This makes it possible to equalize the intensity of the first spot SP1 to the fourth spot SP4, as shown in (d).

[0032] In the above specific example, it was assumed that the first spot SP1 to the fourth spot SP4 were to have the same intensity, but the present invention is not limited to this embodiment. That is, even if a predetermined intensity distribution is given to the first spot SP1 to the fourth spot SP4, the same processing can be performed if the intensity of any of them falls outside the predetermined range. Furthermore, although the example illustrates the correction of variations in laser intensity in the first spot SP1 to the fourth spot SP4, it is also possible to correct variations in spot shape instead, or in conjunction with this. Thus, according to this embodiment, it is possible to feed back the real-time measurement results of the beam profile to laser processing.

[0033] (Second embodiment) The second embodiment will now be described. In describing this embodiment, the differences from the first embodiment will be the main focus. In addition, parts that are the same or equivalent to each other in the first embodiment and this embodiment are denoted by the same reference numerals. Therefore, in the following description of this embodiment, with respect to components that have the same reference numerals as those in the first embodiment, the description in the first embodiment may be appropriately referenced unless there is a technical inconsistency or additional explanation to be provided.

[0034] Referring to Figure 6, in this embodiment, the beam profiler 409 is provided on the processing stage 2 side to measure the beam profile of the laser beam B that has passed through the objective lens 406. In this case, instead of the workpiece W shown in Figure 1, a magnifying optical system 410 is provided on the processing stage 2 side. The magnifying optical system 410 is configured to magnify the laser beam B focused by the objective lens 406 and provide it for measurement by the beam profiler 409. Note that the magnifying optical system 410 may or may not be fixed to the processing stage 2. Furthermore, the control unit 5 controls the operation of the spatial light modulator 403 based on the wavefront measurement results from the wavefront meter 407, as well as the measurement results of the intensity characteristics of the laser beam B using the beam profiler 409.

[0035] Figure 7 shows an example of correcting aberrations and beam profiles while performing beam shaping using the spatial light modulator 403. Note that "beam shaping" includes not only multi-spot formation as shown in Figure 5, but also shaping the beam profile in a single spot (e.g., ring shaping). Here, steps 101 to 103 in Figure 7 are the same as in Figure 4. Therefore, in the following explanation of each process in the flowchart shown in Figure 7, steps 101 to 103 will be omitted, and steps 104 onwards will be explained.

[0036] In step 104, the control unit 5 generates a correction hologram pattern to cancel out aberrations based on the acquired Zernike modes. The control unit 5 then generates a composite hologram pattern by combining this correction hologram pattern with the hologram pattern for beam shaping and displays it on the optical modulation layer of the spatial light modulator 403. In step 105, the control unit 5 measures the wavefront of the laser beam B while the composite hologram pattern is being displayed using the wavefront meter 407. In step 106, the control unit 5 subtracts the wavefront control component for beam shaping from the wavefront data measured in step 105 and performs a Zernike transform to obtain the Zernike coefficients for each term of the Zernike mode in the wavefront aberration of the laser beam B after aberration correction.

[0037] In step 107, the control unit 5 determines whether the wavefront aberration of the laser beam B after aberration correction has reached the desired "flat" state as shown in Figure 3. If the correction is insufficient (i.e., step 107 = NO), the control unit 5 returns to step 104, generates and displays the correction hologram pattern again, and then repeats the processes in steps 105 to 107. If the correction is sufficient (i.e., step 107 = YES), the control unit 5 proceeds to step 108.

[0038] In step 108, the control unit 5 determines the beam profile, i.e., the ratio of major to minor axes and the intensity distribution shape. During the processing in step 108, the focal position may be adjusted as needed. If the ratio of major to minor axes and the intensity distribution shape are not in the desired state (i.e., step 108 = NO), the control unit 5 returns to step 104, corrects the correction hologram pattern to generate and display the composite hologram pattern again, and then repeats the processing in steps 105 to 107. On the other hand, if the beam profile is in the desired state (i.e., step 107 = YES), the control unit 5 terminates the adjustment control operation.

[0039] (Overview of semiconductor wafer manufacturing) Figures 8 to 10 show an overview of so-called laser slicing, in which a semiconductor wafer 601 is cut from a semiconductor ingot 602 by irradiation with a laser beam B, which is a good application of the present invention. Below, an overview of the manufacturing method of semiconductor wafer 601, which is a SiC wafer, by laser slicing will be described.

[0040] To simplify the following explanation, for convenience, we will set the right-handed XYZ coordinate system as shown in Figures 8 to 10. In this right-handed XYZ coordinate system, the Z axis is defined to be parallel to the thickness direction of the semiconductor wafer 601 or the height direction of the semiconductor ingot 602. The height direction of the semiconductor ingot 602 is parallel to the central axis LC in the approximately cylindrical shape of the semiconductor ingot 602. The X and Y axes are assumed to be approximately parallel to the main surface of the semiconductor wafer 601 or the upper and lower end surfaces of the semiconductor ingot 602. The "main surface" is the surface perpendicular to the thickness direction of a plate-like object such as a semiconductor wafer 601, and may also be called the "top surface," "bottom surface," "bottom surface," or "plate surface." In the following explanation, any direction along the main surface of the semiconductor wafer 601 or the upper and lower end surfaces of the semiconductor ingot 602, that is, any direction intersecting the Z axis direction, may be referred to as the "in-plane direction." When the workpiece W is a semiconductor ingot 602, this "in-plane direction" coincides with the "in-plane direction intersecting the irradiation direction of the laser beam B onto the workpiece W" described above. Typically, the main surface of a semiconductor wafer 601 and the upper and lower end surfaces of a semiconductor ingot 602 are nearly horizontal planes that are approximately perpendicular to the Z-axis. Therefore, typically, the "in-plane direction" is any direction perpendicular to the Z-axis, that is, any direction parallel to the XY plane. Furthermore, the direction perpendicular to the in-plane direction may be referred to as the "axial direction" below.

[0041] The semiconductor wafer 601 has a pair of main surfaces, a wafer surface 611 and a wafer surface 612, which are substantially perpendicular to the thickness direction. Similarly, the semiconductor ingot 602 has a pair of end surfaces, an ingot top surface 621 and an ingot bottom surface 622, which are substantially perpendicular to the height direction. This manufacturing method involves forming a delamination layer 623 to a predetermined depth from the ingot top surface 621 by laser irradiation, and obtaining the semiconductor wafer 601 by delaminating the layered wafer precursor 624 between the ingot top surface 621 and the delamination layer 623 from the semiconductor ingot 602 using the delamination layer 623. The delamination surface 625 created by the delamination is flattened by grinding or polishing.

[0042] Figures 9 and 10 show an overview of the process of forming a peel layer 623 by irradiating a semiconductor ingot 602 with a laser beam B. In this process, the laser beam B is irradiated onto the ingot top surface 621, which is the surface of the semiconductor ingot 602, while being moved relative to the semiconductor ingot 602 in the in-plane direction. Here, the laser beam B has a predetermined degree of transparency to the semiconductor ingot 602. Therefore, the focal point SP of the laser beam B can be formed at a predetermined depth from the ingot top surface 621. Thus, by irradiation with the laser beam B, a peel layer 623 is formed at a predetermined depth from the ingot top surface 621, which is the surface of the semiconductor ingot 602, which is the workpiece W, and includes a modified region 626 in which the SiC has been modified by irradiation with the laser beam B. Specifically, the peel layer 623 is formed by the modified region 626 and cracks extending from this modified region 626. The peeled layer 623 formed by such a modified region 626 may also be referred to as the "modified layer."

[0043] The focal point SP of the laser beam B is scanned in the scanning direction Ds, which is one direction in the in-plane direction. This forms a modified region 626 over the entire width of the semiconductor ingot 602 in the scanning direction Ds. The scanning of this focal point SP is then repeated many times while indexing in the line feed direction Df, which is another direction in the in-plane direction and is perpendicular to the scanning direction Ds, so that the laser beam B irradiates almost the entire surface of the ingot top surface 621, thereby forming a delamination layer 623. Here, as shown in Figure 9, the formation process of the delamination layer 623 can be made more efficient by simultaneously forming multiple focal points SP of the laser beam B at different positions in the line feed direction Df. Figures 9 and 10 show an example in which multiple focal points SP are scanned while being arranged in a line in a direction inclined with respect to the scanning direction Ds and the line feed direction Df.

[0044] However, if errors, fluctuations, or variations occur in the depth of the focusing point SP from the ingot top surface 621, the depth of the modified region 626, i.e., its axial position, will fluctuate. This increases the unevenness of the delamination layer 623, i.e., the delamination surface 625, which increases the processing allowance for grinding and polishing after delamination, worsening the material yield and reducing productivity. Therefore, it is preferable to homogenize the characteristics such as intensity at each of the multiple focusing points SP by beam shaping and aberration correction using wavefront control. This makes it possible to further improve productivity in wafer manufacturing technology, in which a semiconductor wafer 601 is obtained from a semiconductor ingot 602 by laser slicing, compared to conventional methods.

[0045] (modified version) The present invention is not limited to the embodiments described above. Therefore, the embodiments can be modified as appropriate. Representative modifications are described below. In the following description of modifications, the differences from the embodiments will be mainly described. In addition, parts that are the same or equivalent to each other in the embodiments and modifications are denoted by the same reference numerals. Therefore, in the following description of modifications, with respect to components that have the same reference numerals as in the embodiments, the descriptions in the embodiments can be appropriately applied unless there is a technical inconsistency or additional explanation is required.

[0046] The present invention is not limited to the embodiments described above. That is, for example, there are no particular limitations on the shape of the optical path BL of the laser beam B in the laser processing apparatus 1, specifically, whether or not there are mirrors for reversal, the number of reversals, and the direction of path change. Therefore, for example, the portion of the optical path BL of the laser beam B between the intermediate optical element portion 401 and the irradiation portion 405 and the portion between the irradiation portion 405 and the objective lens 406 do not have to be in the same plane. Typically, for example, the former may be parallel to the support surface supporting the optical system 4 on a base (not shown) that supports the optical system 4, and the latter may be perpendicular to the support surface. Furthermore, the application target of the laser processing apparatus 1 is not limited to laser slicing. That is, the present invention can be well applied not only to laser slicing but also to laser dicing. There are also no particular limitations on the wavelength of the laser beam B. Therefore, the present invention can be well applied, for example, to precise drilling and removal processing by laser ablation. There are no particular limitations on the method of fixing the workpiece W to the processing stage 2; any method such as air adsorption, electrostatic adsorption, double-sided tape fixing, or adhesive bonding can be used.

[0047] The relative movement between the workpiece W and the irradiation unit 405 and objective lens 406 that irradiate the workpiece W with a laser beam B may be fixed and the latter movable, or vice versa, or both may be movable. There are no particular limitations on the configuration, number, or arrangement of optical elements along the optical path BL. Specifically, for example, the spatial light modulator 403 is not limited to LCOS-SLM and may have other structures. Also, the first telescope optical system 404 may be omitted. Furthermore, the irradiation unit 405 may be a beam splitter. Alternatively, the irradiation unit 405 may be a galvanometer mirror. The irradiation unit 405 and the objective lens 406 may be unitized by being housed and supported in the same housing. Furthermore, although the wavefront data was acquired as a Zernike polynomial in the above embodiment, it is not limited to this. For example, the wavefront data may be acquired as Seidel's five aberrations or Legendre polynomials, etc.

[0048] It goes without saying that the elements constituting the above embodiments are not necessarily essential, except when explicitly stated to be particularly essential or when they are clearly considered essential in principle. Furthermore, when numerical values ​​such as the number, quantity, or range of components are mentioned, the present invention is not limited to those specific numerical values, except when explicitly stated to be particularly essential or when it is clearly limited in principle to those specific numerical values. Similarly, when the shape, direction, positional relationship, etc., of components are mentioned, the present invention is not limited to those shape, direction, positional relationship, etc., except when explicitly stated to be particularly essential or when it is clearly limited in principle to those specific shape, direction, positional relationship, etc. Modifications are not limited to the examples given above. That is, for example, all or part of each of the multiple embodiments can be combined with each other, as long as they do not contradict each other technically. Similarly, multiple modifications can be combined with each other, as long as they do not contradict each other technically.

[0049] (Perspective) As is evident from the above-described descriptions of the configuration and operation relating to the embodiments and modifications, the disclosure herein includes at least the following aspects: [Perspective 1] A laser processing apparatus (1) is configured to perform laser processing on a workpiece (W) by irradiating the workpiece with a laser beam (B), A laser oscillator (3) that outputs the aforementioned laser beam, An irradiation unit (405) is provided to direct the laser beam output from the laser oscillator toward the workpiece, A spatial light modulator (403) is provided in the optical path (BL) of the laser beam between the laser oscillator and the irradiation unit, A control unit (5) is provided to control the operation of the spatial light modulator based on the wavefront measurement results obtained by a wavefront meter (407) that measures the wavefront of the laser beam, Equipped with, The irradiation unit is configured to generate stray light (BM) which is a portion of the incident laser beam that does not go toward the workpiece. The wavefront meter is provided to measure the wavefront of the leaked light, Laser processing equipment. [Perspective 2] The wavefront meter is provided so as to be in a conjugate relationship with the workpiece. The laser processing apparatus described in Perspective 1. [Perspective 3] The control unit further controls the operation of the spatial light modulator based on the measurement results of the intensity characteristics of the laser beam using a beam profiler (49). A laser processing apparatus as described in perspective 1 or 2. [Perspective 4] The control unit further monitors aging degradation based on the operating control state of the spatial light modulator and the wavefront measurement results from the wavefront meter. A laser processing apparatus described in any one of the following three points. [Perspective 5] The system is configured to simultaneously irradiate multiple different positions in an in-plane direction intersecting the irradiation direction of the laser beam onto the workpiece. A laser processing apparatus described in any one of the following points 1 to 4. [Perspective 6] The laser beam is irradiated to form a modified layer (623) to a predetermined depth from the surface (621) of the semiconductor (602) to be processed. A laser processing apparatus described in any one of the following points 1 to 5. [perspective 7] A method for adjusting a laser processing apparatus (1) configured to perform laser processing on a workpiece (W) by irradiating the workpiece with a laser beam (B), The aforementioned laser processing apparatus is A laser oscillator (3) that outputs the aforementioned laser beam, An irradiation unit (405) is provided to direct the laser beam output from the laser oscillator toward the workpiece, A spatial light modulator (403) is provided in the optical path (BL) of the laser beam between the laser oscillator and the irradiation unit, Equipped with, The wavefront of a portion of the laser beam incident on the irradiation unit that is not directed toward the workpiece (BM) is measured by a wavefront meter (407). Based on the wavefront measurement results from the wavefront meter, the operation of the spatial light modulator is controlled. How to adjust a laser processing device. [Perspective 8] The wavefront meter is installed so as to be conjugate to the workpiece. A method for adjusting the laser processing apparatus described in Perspective 7. [Perspective 9] Based on the measurement results of the intensity characteristics of the laser beam using a beam profiler (409), the operation of the spatial light modulator is controlled. A method for adjusting a laser processing apparatus as described in perspective 7 or 8. [Perspective 10] Based on the operational control state of the spatial light modulator and the wavefront measurement results from the wavefront meter, the system monitors deterioration over time. A method for adjusting a laser processing apparatus as described in any one of viewpoints 7 to 9. [Perspective 11] The laser processing apparatus is configured to simultaneously irradiate the workpiece with the laser beam at multiple different positions in an in-plane direction intersecting the irradiation direction of the laser beam. A method for adjusting a laser processing apparatus as described in any one of the viewpoints 7 to 10. [Perspective 12] The laser processing apparatus is configured to form a modified layer (623) to a predetermined depth from the surface (621) of the semiconductor (602) to be processed by irradiation with the laser beam. A method for adjusting a laser processing apparatus as described in any one of the viewpoints 7 to 11. [Explanation of symbols]

[0050] 1. Laser processing device 3. Laser Oscillator 403 Spatial Light Modulator 405 Irradiation area 407 Wavefront meter 409 Beam Profiler 5. Control Unit B Laser beam BL light path W Workpiece

Claims

1. A laser processing apparatus (1) is configured to perform laser processing on a workpiece (W) by irradiating the workpiece with a laser beam (B), A laser oscillator (3) that outputs the aforementioned laser beam, An irradiation unit (405) is provided to direct the laser beam output from the laser oscillator toward the workpiece, A spatial light modulator (403) is provided in the optical path (BL) of the laser beam between the laser oscillator and the irradiation unit, A control unit (5) is provided to control the operation of the spatial light modulator based on the wavefront measurement results obtained by a wavefront meter (407) that measures the wavefront of the laser beam, Equipped with, The irradiation unit is configured to generate stray light (BM) which is a portion of the incident laser beam that does not go toward the workpiece. The wavefront meter is provided to measure the wavefront of the leaked light, The control unit further monitors aging degradation based on the operating control state of the spatial light modulator and the wavefront measurement results from the wavefront meter. Laser processing equipment.

2. The wavefront meter is provided so as to be in a conjugate relationship with the workpiece. The laser processing apparatus according to claim 1.

3. The control unit further controls the operation of the spatial light modulator based on the measurement results of the intensity characteristics of the laser beam using a beam profiler (49). The laser processing apparatus according to claim 1.

4. The system is configured to simultaneously irradiate multiple different positions in an in-plane direction intersecting the irradiation direction of the laser beam onto the workpiece. The laser processing apparatus according to claim 1.

5. The laser beam is irradiated to form a modified layer (623) to a predetermined depth from the surface (621) of the semiconductor (602) to be processed, The laser processing apparatus according to claim 1.

6. A method for adjusting a laser processing apparatus (1) configured to perform laser processing on a workpiece (W) by irradiating the workpiece with a laser beam (B), The aforementioned laser processing apparatus is A laser oscillator (3) that outputs the aforementioned laser beam, An irradiation unit (405) is provided to direct the laser beam output from the laser oscillator toward the workpiece, A spatial light modulator (403) is provided in the optical path (BL) of the laser beam between the laser oscillator and the irradiation unit, Equipped with, The wavefront of a portion of the laser beam incident on the irradiation unit that is not directed toward the workpiece (BM) is measured by a wavefront meter (407). Based on the wavefront measurement results from the wavefront meter, the operation of the spatial light modulator is controlled. Based on the operational control state of the spatial light modulator and the wavefront measurement results from the wavefront meter, the system monitors deterioration over time. How to adjust a laser processing device.

7. The wavefront meter is installed so as to be conjugate to the workpiece. A method for adjusting a laser processing apparatus according to claim 6.

8. Based on the measurement results of the intensity characteristics of the laser beam using a beam profiler (409), the operation of the spatial light modulator is controlled. A method for adjusting a laser processing apparatus according to claim 6.

9. The laser processing apparatus is configured to simultaneously irradiate the workpiece with the laser beam at multiple different positions in an in-plane direction intersecting the irradiation direction of the laser beam. A method for adjusting a laser processing apparatus according to claim 6.

10. The laser processing apparatus is configured to form a modified layer (623) to a predetermined depth from the surface (621) of the semiconductor (602) to be processed by irradiation with the laser beam. A method for adjusting a laser processing apparatus according to claim 6.

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