Laser processing apparatus

Abstract

The disclosed laser processing apparatus comprises: a beam splitter for splitting a laser beam from a light source into a first beam having a first polarization and a second beam having a second polarization; a beam converter for changing the beam mode of at least one of the first beam and the second beam; a beam combiner for overlapping the first and second beams on the same optical path; and a projection optical system for projecting the overlapped first and second beams onto an object being processed.

Description

Laser processing device

[0001] The present disclosure relates to a laser processing device.

[0002] In semiconductor manufacturing, glass substrates, silicon substrates, sapphire substrates, and other substrates are used as wafers. During the semiconductor manufacturing process, a process of cutting the wafer is necessary, either during the preparation process or after the semiconductor manufacturing process is complete, to individually separate the multiple circuit elements formed on the wafer. Cutting methods include mechanical cutting and laser cutting. Mechanical cutting involves cutting the wafer using a rotating saw blade. Mechanical cutting carries the risk of damaging the circuit elements on the wafer due to debris generated during the cutting process. Furthermore, mechanical cutting has the disadvantage of being very slow, requiring blade replacement costs and time due to blade wear. Furthermore, microcracks can form near the cut line. Laser cutting involves laser full cutting, which completely cuts the wafer. A hybrid cutting method involves forming grooves on the wafer using a laser, followed by complete cutting using a rotating saw blade.

[0003] The characteristics of the laser processing beam itself or its beam mode can affect processing quality. For example, continuous processing using a processing beam with an asymmetric intensity profile can result in asymmetric processing, such as a decrease in the flatness of the groove bottom. Heat-affected zones (HAZs) and recasts may also occur on the edges of the workpiece perpendicular to the processing direction, requiring additional processing to remove these defects.

[0004] Depending on the characteristics of the object being processed or the processing objective, adjustments to processing beam conditions, such as beam width and intensity profile, may be necessary. The optical systems of typical laser processing devices have fixed optical elements, making it difficult to flexibly change processing beam conditions according to the characteristics of the object being processed or the processing objective.

[0005] The present disclosure aims to provide a laser processing device capable of preventing deterioration of processing quality caused by asymmetry of a processing beam.

[0006] The present disclosure aims to provide a laser processing device capable of reducing heat-affected zone and recast.

[0007] The present disclosure aims to provide a laser processing device that can flexibly respond to the characteristics of a processing object or a processing goal.

[0008] A laser processing device according to one aspect of the present disclosure comprises: a light source; a beam splitter that splits a laser beam from the light source into a first beam having a first polarization and a second beam having a second polarization; a beam converter that changes a beam mode of at least one of the first beam and the second beam; a beam combiner that overlaps the first beam and the second beam in the same optical path; and a projection optical system that projects the overlapped first beam and the second beam onto a processing object.

[0009] As an example, the beam splitter may include a polarizing beam splitter.

[0010] In one embodiment, the beam converter can rotate or flip at least one of the first beam and the second beam so that the first beam and the second beam have different intensity profiles.

[0011] As one embodiment, the beam converter can rotate at least one of the first beam and the second beam about the optical axis.

[0012] As one embodiment, the beam converter may include a dove prism.

[0013] As an example, the rotation angle of at least one of the first beam and the second beam can be adjusted by rotating the dove prism.

[0014] As one embodiment, the beam converter can invert at least one of the first beam and the second beam.

[0015] As one embodiment, the laser processing device may include a beam diameter adjuster that adjusts a beam diameter of at least one of the first and second beams to adjust a focal depth of at least one of the first beam and the second beam.

[0016] As one embodiment, the laser processing device may include a beam intensity controller disposed between the light source and the beam splitter to adjust the intensity of the first beam and the second beam by changing the polarization characteristics of the laser beam.

[0017] As one embodiment, the laser processing device may include at least one scanner that moves at least one of the first and second beams in a direction orthogonal to the processing direction.

[0018] As an example, the laser processing device can process the object to be processed while moving at least one of the first beam and the second beam in a direction orthogonal to the processing direction.

[0019] As one embodiment, the laser processing device can process the object to be processed while moving at least one of the first beam and the second beam in a direction orthogonal to the processing direction.

[0020] As an example, the projection optical system may include a telecentric lens that irradiates a beam parallel to the optical axis to the processing object regardless of the incident angles of the first beam and the second beam.

[0021] According to embodiments of the laser processing device of the present disclosure, a laser beam is split into two beams based on a polarization direction, and at least one of the two split beams is reversed or rotated, and then the two beams are combined and irradiated onto a processing object, thereby preventing a deterioration in processing quality due to unevenness or asymmetry in the intensity distribution of the laser beam.

[0022] According to embodiments of the laser processing device of the present disclosure, the depth of focus of the processing beam can be expanded by adjusting the beam diameter of at least one of the two split beams to control the depth of focus of the two split beams. This enables stable processing that is less sensitive to the flatness of the processing target.

[0023] According to embodiments of the laser processing device of the present disclosure, by changing the polarization characteristics of the laser beam, the intensity ratio of the two split beams can be adjusted so as to achieve optimal processing quality according to the characteristics of the object to be processed, the processing goal, etc. In addition, it is possible to easily form an optimal processing beam while minimizing changes in the optical system, and to implement a laser processing device having stable processing quality.

[0024] According to embodiments of the laser processing device of the present disclosure, it is possible to form a processing beam suitable for a target processing width by controlling the degree of overlap between two beams divided using a scanner.

[0025] According to embodiments of the laser processing device of the present disclosure, the heat affected zone and recast can be reduced by moving at least one of the two split beams in a direction orthogonal to the processing direction using a scanner.

[0026] According to embodiments of the laser processing device of the present disclosure, without changing the optical system, the rotation angle (or the angle of the axis of reversal) of at least one of the two split beams, the degree of overlap of the two beams, the depth of focus of the two beams, the polarization ratio of the laser beam before splitting, etc. can be adjusted according to the type of processing or the processing target, so that a laser processing device with a high degree of freedom and capable of various processing can be implemented.

[0027] FIG. 1 is a schematic diagram of a laser processing device according to one embodiment of the present disclosure.

[0028] Figure 2 is a schematic diagram of one embodiment of a beam converter.

[0029] Figure 3 exemplarily shows the deterioration of processing quality due to the asymmetry of the intensity profile of the laser beam.

[0030] FIG. 4 is a schematic diagram of a laser processing device according to one embodiment of the present disclosure.

[0031] FIG. 5 is a schematic diagram of a laser processing device according to one embodiment of the present disclosure.

[0032] FIG. 6 is a schematic diagram of a laser processing device according to one embodiment of the present disclosure.

[0033] Figure 7 is a drawing illustrating an example of a process for adjusting the processing width by moving the first beam and / or the second beam.

[0034] Figure 8 is a drawing showing an example of deterioration in processing quality due to a processed product.

[0035] FIG. 9 is a schematic cross-sectional view showing an example of a laser processing process according to an embodiment of the laser processing device illustrated in FIG. 6.

[0036] FIG. 10 is a schematic plan view showing an example of a laser processing process according to an embodiment of the laser processing device illustrated in FIG. 6.

[0037] Figure 11 is a schematic flowchart of one embodiment of a laser processing method.

[0038] Figure 12 is a schematic flowchart of one embodiment of a laser processing method.

[0039] Figure 13 is a schematic flowchart of one embodiment of a laser processing method.

[0040] Figure 14 is a schematic flowchart of one embodiment of a laser processing method.

[0041] Hereinafter, embodiments of the laser processing method and device according to the present disclosure will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals denote the same components, and the size or thickness of each component may be exaggerated for clarity of explanation. In addition, for convenience of illustration in FIGS. 1, 3, and 6, the optical path lengths of the first beam and the second beam, which will be described later, are depicted differently, but the optical path lengths of the first beam and the second beam are the same.

[0042] FIG. 1 is a schematic diagram of a laser processing device according to one embodiment of the present disclosure. Referring to FIG. 1, the laser processing device may include a stage (100), a light source (200), a beam splitter (310), a beam converter (320), a beam combiner (330), and a projection optical system (400). Reference numerals 361, 362, 363, 364, 365, 366, and 367 represent reflection mirrors.

[0043] A machining target (1) is mounted on a stage (100). The machining target (1) may be, for example, a wafer used in a semiconductor process, such as a glass substrate, a silicon substrate, or a sapphire substrate. The machining target (1) may be a wafer before a semiconductor process is performed. The machining target (1) may be a wafer having a plurality of circuit elements formed on the surface by a series of semiconductor processes. Although not depicted in the drawing, a fixing means for fixing the machining target (1) to the stage (100) may be provided. For example, the fixing means may be a vacuum chuck.

[0044] The stage (100) can be moved laterally, for example, in the X direction, or in the X and Y directions, by means of a moving means not shown. Additionally, the stage (100) can be moved in the Z direction perpendicular to the X and Y directions. Additionally, the stage (100) can be rotated about the Z direction as an axis. For example, by moving the stage (100) in the Y direction, a machining result such as a groove extending in the Y direction can be formed. Then, by rotating the stage (100) 90 degrees with respect to the Z direction and moving the stage (100) in the Y direction, a machining result such as a groove extending in the X direction can be formed as a result. In this case, the Y direction is referred to as the machining direction.

[0045] The light source (200) generates, for example, a laser beam (L). The laser beam (L) may be, for example, collimated light. As an example, the laser beam (L) may be an ultrashort pulse laser beam having a pulse width of 1 μs or less, for example, a nanosecond order, a picosecond order, or a femtosecond order. For example, the peak power density of the laser beam (L) having a pulse width of a femtosecond order is 1×10 8 (W / ㎠) or more, and the peak power density of the laser beam with a pulse width on the order of nanoseconds or picoseconds may be lower than this. Such a laser beam (L) has very high focusing properties and can focus up to the diffraction limit. However, this is not limited to this, and the laser beam (L) may also be a continuous laser beam.

[0046] The beam splitter (310) splits the laser beam (L) into a first beam (L1) and a second beam (L2). For example, the beam splitter (300) can split the laser beam (L) into a first beam (L1) and a second beam (L2) having different polarization directions. The first beam (L1) can have a polarization direction that is orthogonal to the polarization direction of the second beam (L2). The first beam (L1) can be a first polarization beam, and the second beam (L2) can be a second polarization beam. The beam splitter (310) can include, for example, a cube-type PBS (polarization beam splitter) having a polarization plane (311). Among the laser beams (L) incident on the beam splitter (310), the beam of the first polarization component transmits the polarization plane (311) of the beam splitter (310), and the beam of the second polarization component is reflected from the polarization plane (311) of the beam splitter (310). For example, the first polarization beam and the second polarization beam may be linearly polarized beams whose vibration planes are orthogonal to each other. For example, the first polarization beam may be a P-polarization beam, and the second polarization beam may be an S-polarization beam. In the present embodiment, the first beam (L1) is a P-polarization beam, and the second beam (L2) is an S-polarization beam. The polarization plane (311) may transmit the P-polarization beam and reflect the S-polarization beam.

[0047] The beam converter (320) converts at least one beam mode among the first beam (L1) and the second beam (L2). In this embodiment, the beam converter (320) is arranged in the propagation path of the second beam (L2) to convert the beam mode of the second beam (L2), but is not limited thereto. Although not illustrated in the drawing, the beam converter (320) may be arranged in the propagation path of the first beam (L1) to convert the beam mode of the first beam (L1), and may be arranged in the propagation path of the first beam (L1) and the propagation path of the second beam (L2) to convert the beam modes of both the first and second beams (L1) (L2). Here, converting the beam mode means inverting the input beam in any direction orthogonal to the optical axis or rotating it around the optical axis, and as a result, the intensity profile of the output beam becomes a form in which the intensity profile of the input beam is inverted or rotated. Rotating it around the optical axis means that the direction of inversion is rotated. As a result, the beam converter (320) inverts at least one of the first beam (L1) and the second beam (L2) around the optical axis or By rotating, the first beam (L1) and the second beam (L2) have different intensity profiles in a direction orthogonal to the processing direction (e.g., X direction), or in a direction orthogonal to the processing direction (e.g., X direction) and a processing direction (e.g., Y direction). In other words, the beam converter (320) inverts or rotates at least one of the first beam (L1) and the second beam (L2) to make the intensity profiles of the first beam (L1) and the second beam (L2) inconsistent. In the present embodiment, the beam mode converter (320) can invert or rotate the second beam (L2) about the optical axis.

[0048] Figure 2 is a schematic diagram of one embodiment of a beam converter (320). Referring to Figure 2, the beam converter (320) may include a dove prism (321). The input beam (L in ) is incident on the dove prism (321) through the input slope (321-1), and is flipped upside down to form an output beam (L out) is emitted from the output slope (321-2). Although not shown in the drawing, if the dove prism (321) is positioned in a 90-degree rotated state, the input beam (L) incident on the dove prism (321) through the input slope (321-1) in ) is inverted left and right and outputs the beam (L out ) is emitted from the output slope (321-2).

[0049] Dove prism (321) on the optical axis (L axis ) can be rotated around the optical axis (L). The rotation angle of the second beam (L2) can be adjusted by rotating the dove prism (321) around the optical axis (L) using a rotating means, for example, a motor (322). axis ) is rotated around the optical axis (L). axis ) is rotated within a plane orthogonal to the optical axis (L), and the second beam (L2) is rotated along the optical axis (L axis ) can be rotated around the optical axis (L). Although not shown in Fig. 2, the dove prism (321) is supported on a cylindrical holder, and the motor (322) can rotate the holder. For example, when the dove prism (321) is rotated 90 degrees, the axis of reversal is centered on the optical axis (L axis ) is rotated 90 degrees in a plane orthogonal to the incident beam (L in ) is flipped left and right and the output beam (L out) is output as. As a result, the beam converter (320) can rotate and invert the second beam (L2) at an arbitrary angle around the optical axis. For example, if a target rotation angle of the dove prism (321) is input through an input means (not shown), the control unit (not shown) can control the motor (322) according to the input rotation angle to rotate the dove prism (321) by the target rotation angle. Although not shown in the drawing, the dove prism (321) can also be rotated by manual operation instead of using the motor (322). The rotation angle of the dove prism (321) can be determined so as to form a processing beam (L3) having optimal conditions according to the shape of the intensity profile of the laser beam (L), the characteristics of the processing object (1), and the processing target.

[0050] The beam combiner (330) combines, or in other words, superimposes, the first beam (L1) and the second beam (L2) by guiding them along the same optical path to form a processing beam (L3). For example, the beam combiner (330) may be a polarization beam combiner. The beam combiner (330) may include, for example, a cube-type polarization beam combiner (PBC) having a polarization plane (331). In the present embodiment, the first beam (L1) is a P-polarized beam, and the second beam (L2) is an S-polarized beam, so the polarization plane (331) can reflect the P-polarized beam and transmit the S-polarized beam. The first beam (L1) is reflected from the polarizing surface (331) of the beam combiner (330) and proceeds to the projection optical path, and the second beam (L2) passes through the polarizing surface (311) of the beam combiner (330) and proceeds to the projection optical path. Accordingly, the first beam (L1) and the second beam (L2) overlap and are incident on the projection optical system (400) along the projection optical path as a processing beam (L3).

[0051] The projection optical system (400) focuses the processing beam (L3) onto the processing target (1). The projection optical system (400) may include one or more focusing lenses. When dicing processing is performed, the processing beam (L3) may have a Gaussian intensity profile. When grooving processing is performed, the processing beam (L3) may have a flat-top intensity profile. To this end, the projection optical system (400) may further include a D-lens (diffraction lens) arranged upstream of the focusing lens to convert the Gaussian intensity profile into a flat-top intensity profile.

[0052] One or more focusing lenses may include, for example, a telecentric lens. The telecentric lens projects a beam parallel to the optical axis onto the object to be processed (1) regardless of the incidence angles of the first and second beams (L1) (L2) incident on the projection optical system (40). In other words, the telecentric lens causes the first beam (L1) and the second beam (L2) to be incident perpendicularly onto the processing surface of the object to be processed (1) regardless of the incidence angles of the first and second beams (L1) (L2) incident on the projection optical system (40). Ideally, the first beam (L1) and the second beam (L2) are parallel to the optical axis of the projection optical system (400), but they may be incident on the projection optical system (400) at an angle with respect to the optical axis of the projection optical system (400) due to processing errors, installation angle errors, etc. of optical members arranged on the optical path from the light source (200) to the projection optical system (400). Then, the first beam (L1) and / or the second beam (L2) may not be incident perpendicularly to the processing surface of the processing object (1). Then, the processing quality by the first beam (L1) and the second beam (L2) may become non-uniform. By employing a projection optical system (400) including a telecentric lens, the first and second beams (L1) (L2) can be incident perpendicularly to the processing surface of the processing object (1), so that the first and second beams (L1) (L2) can be projected onto the processing object (1) with the same quality.

[0053] Fig. 3 shows an example of a deterioration in processing quality due to the asymmetry of the intensity profile of the laser beam (L). The laser beam (L) may have various beam modes, for example, intensity profiles, depending on the type of the processing object (1), the purpose of processing, etc. The intensity profile of the laser beam (L) is oriented along the optical axis (L axis ) needs to be symmetrical in the direction (e.g. X direction) orthogonal to the processing direction (e.g. Y direction). For example, the intensity profile of the laser beam (L) must be symmetrical with respect to the optical axis (L axis ) is asymmetrical in the X direction based on the groove (10), the processing result, for example, the X-direction edges (12)(13) of the groove (10), may be processed asymmetrically. In addition, if an intensity peak exists at a specific position in the X direction in the intensity profile of the laser beam (L), the energy of the laser beam (L3) is concentrated at a position corresponding to the intensity peak while the laser beam (L) is reciprocated in the processing direction, i.e., the Y direction, multiple times, so that the portion may be excessively processed compared to other portions. As a result, as shown in (a) of FIG. 3, a wedge-shaped groove (14) may be formed at the bottom (11') of the groove (10). The groove (14) may extend linearly in the Y direction, which is the processing direction. A crack may occur from the groove (14). If the crack progresses to the lower surface of the processing object (1), the processing object (1) may be damaged. If the crack progresses in an undesirable direction, for example, circuit elements formed on the surface of the workpiece (1) may be damaged. In addition, if the intensity profile of the laser beam (L) is non-uniform in the X direction, the flatness of the bottom (11') of the groove (10) may be reduced, as shown in (a) of Fig. 3.

[0054] According to the laser processing device of the present embodiment, the laser beam (L) is split into first and second beams (L1) (L2), and the second beam (L2) is inverted about the optical axis. Then, the first and second beams (L1) (L2) are combined. The axis of inversion can be determined, for example, by the rotation angle of the dove prism (321). For example, the second beam (L2) can be inverted in a direction orthogonal to the processing direction, for example, in the X direction. In other words, by rotating the dove prism (321) by 90 degrees, the second beam (L2) can be inverted in the X direction, and as a result, the second beam (L2) can be rotated by 180 degrees. Accordingly, the intensity profiles of the first beam (L1) and the second beam (L2) become inconsistent with each other, for example, inverted with each other in the X direction. By overlapping the first beam (L1) and the second beam (L2), the intensity profile of the processing beam (L3) can be made symmetrical in the X direction, and the unevenness of the intensity along the X direction can be alleviated. Therefore, for example, in grooving processing or dicing processing (not shown), both edges in the X direction can be processed symmetrically. In addition, as illustrated in (b) of Fig. 3, in the case of grooving processing, the occurrence of a groove (14) in the bottom (11) of the groove (10) can be reduced, and the flatness of the bottom (11) can be improved.

[0055] In addition, according to the laser processing device of the present embodiment, since the first and second beams (L1) (L2) having polarizations orthogonal to each other are combined and superimposed, interference between the first and second beams (L1) (L2) does not occur during the combining process. Accordingly, deterioration of processing quality due to interference during the combining process of the two beams can be prevented.

[0056] As an example, the case of rotating the second beam (L2) by 180 degrees has been described, but the rotation angle of the second beam (L2) is not limited thereto. The rotation angle of the second beam (L2) can be determined so as to form a processing beam (L3) having optimal conditions depending on the shape of the intensity profile of the laser beam (L), the characteristics of the processing target (1), and the processing goal.

[0057] In the manufacture of a laser processing device, there may be a certain degree of variation in the characteristics of the light source (200). According to the laser processing device of the present embodiment, the optimal processing beam (L3) can be formed by rotating the beam converter (320) in consideration of the characteristics of the light source (200). Therefore, the optimal processing beam (L3) can be easily formed while minimizing changes to the optical system, and a laser processing device with stable processing quality can be implemented. In addition, when the characteristics of the light source (200) currently in use do not match the characteristics of the object to be processed (1) or the processing goal, replacing the light source (200) itself may incur costs. According to the laser processing device of the present embodiment, after splitting the laser beam (L) into two, one or both of them is rotated around the optical axis and then recombined, a processing beam (L3) that matches the characteristics of the object to be processed (1) or the processing goal can be generated. This enables cost reduction.

[0058] FIG. 4 is a schematic diagram of a laser processing device according to one embodiment of the present disclosure. The embodiment of the laser processing device illustrated in FIG. 4 differs from the embodiment of the laser processing device illustrated in FIG. 1 in that it includes means for adjusting the intensity ratio of the first beam (L1) and the second beam (L2). Hereinafter, components having the same function are denoted by the same reference numerals, and redundant descriptions are omitted, with the differences being primarily described.

[0059] Referring to FIG. 4, the laser processing device of the present embodiment has a beam intensity controller that controls the intensities of the first beam (L1) and the second beam (L2). The beam intensity controller controls the intensity ratio of the first beam (L1) and the second beam (L2) by changing the polarization characteristics of the laser beam (L). As a result, the intensities of the first beam (L1) and the second beam (L2) can be controlled. As an example, the beam intensity controller may include a half-wave plate (350). The half-wave plate (350) is arranged between the light source (200) and the beam splitter (310). By rotating the half-wave plate (350), the polarization characteristics of the laser beam (L) can be changed, and thereby the intensities of the P-polarization component and the S-polarization component of the laser beam (L) can be continuously controlled. Considering the characteristics of the object to be processed (1), the processing goal, etc., the intensity ratio of the first beam (L1) and the second beam (L2) can be adjusted, and only one of the first beam (L1) and the second beam (L2) can be used for processing as needed.

[0060] For example, the half-wave plate (350) can be supported on a holder (not shown), and for example, a motor (351) can rotate the holder. For example, when a target rotation angle of the half-wave plate (350) is input through an input means (not shown), the control unit (not shown) can control the motor (351) according to the input rotation angle to rotate the half-wave plate (350) by the target rotation angle. Although not shown in the drawing, the half-wave plate (350) can also be rotated by manual operation instead of using the motor (351).

[0061] By this configuration, the intensity of the first and second beams (L1) (L2) can be adjusted so as to implement optimal processing quality according to the characteristics of the processing target (1), the processing goal, etc. In addition, it is possible to easily form an optimal processing beam (L3) while minimizing changes in the optical system, and implement a laser processing device having stable processing quality.

[0062] FIG. 5 is a schematic diagram of a laser processing device according to one embodiment of the present disclosure. The embodiment of the laser processing device illustrated in FIG. 5 differs from the embodiment of the laser processing device illustrated in FIG. 4 in that it includes means for adjusting the beam diameter of at least one of the first beam (L1) and the second beam (L2). Hereinafter, components having the same function are denoted by the same reference numerals, and redundant descriptions are omitted, with the differences being primarily described.

[0063] Referring to FIG. 5, the laser processing device of the present embodiment has a beam diameter controller (340) that controls the beam diameter, or divergence, of at least one of the first beam (L1) and the second beam (L2) to control the depth of focus of at least one of the first beam (L1) and the second beam (L2). For example, the beam diameter controller (340) in the present embodiment includes a first beam expander (341) that controls the beam diameter of the first beam (L1) and a second beam expander (342) that controls the beam diameter of the second beam (L2). The first and second beam expanders (341)(342) may include, for example, one or more zoom lenses. The beam diameter controller (340) may control the beam diameters of the first beam (L1) and the second beam (L2) differently from each other. Accordingly, the focal depth of the first beam (L1) and the focal depth of the second beam (L2) become different. That is, the depth of focus (DOF) of the processing beam (L3) formed by overlapping the first and second beams (L1) (L2) can be expanded. The flatness of the processing object (1) can affect the processing quality. If the flatness of the processing object (1) becomes greater than the depth of focus, the processing quality can deteriorate. According to the present embodiment, the depth of focus of the processing beam (L3) can be expanded by making the beam diameters of the first beam (L1) and the second beam (L2) different from each other, so that processing that is less sensitive to the flatness of the processing object (1) is possible, and stable processing quality can be implemented even if the flatness of the processing object (1) is partially uneven. In addition, in the case of grooving processing, the depth of focus of the processing beam (L3) can be made relatively shallow, and in the case of dicing processing, the depth of focus of the processing beam (L3) can be made relatively deep to effectively respond to the processing target.

[0064] Although not illustrated in the drawing, the beam adjuster (340) can be applied to the embodiment of the laser processing device illustrated in FIG. 1.

[0065] FIG. 6 is a schematic diagram of a laser processing device according to one embodiment of the present disclosure. The embodiment of the laser processing device illustrated in FIG. 6 differs from the embodiment of the laser processing device illustrated in FIG. 5 in that it includes means for moving at least one of the first beam (L1) and the second beam (L2) in a direction orthogonal to the processing direction. Hereinafter, components having the same function are denoted by the same reference numerals, and redundant descriptions are omitted, with the differences being primarily described.

[0066] Referring to FIG. 6, the laser processing device of the present embodiment has at least one scanner (370) that moves at least one of the first beam (L1) and the second beam (L2) in a direction orthogonal to the processing direction. By moving the first beam (L1) and / or the second beam (L2) in the X direction, the processing width of the processing beam (L3) can be adjusted. The scanner (370) may, for example, vibrate at least one of the first beam (L1) and the second beam (L2) in a direction orthogonal to the processing direction, that is, in the X direction. The width of the movement (or vibration) can be appropriately adjusted according to the characteristics of the processing object (1), the processing target, the processing state, etc.

[0067] The scanner (370) may include a first scanner (371) that moves the first beam (L1). For example, the first scanner (371) may include a first reflection mirror (371a) and a first scanner motor (371b) that vibrates the first reflection mirror (371a). The first reflection mirror (371a) may be fixed to a rotational axis of the scanner motor (371b). By rotating the first scanner motor (371a), the first reflection mirror (371a) may be rotated in the X direction about the Y-direction axis, thereby moving the first beam (L1) in the X direction. In addition, by rotating the first scanner motor (371a) forward / reverse, the first reflection mirror (371a) may be oscillated in the X direction about the Y-direction axis, thereby vibrating the first beam (L1) in the X direction.

[0068] The scanner (370) may further include a second scanner (372) that vibrates the second beam (L2). The second scanner (372) may include a second reflective mirror (372a) and a second scanner motor (372b) that vibrates the second reflective mirror (372a). The second reflective mirror (372a) may be fixed to a rotational axis of the scanner motor (372b). By rotating the second scanner motor (372a), the second reflective mirror (372a) may be rotated in the X direction about the Y-direction axis, thereby moving the second beam (L2) in the X direction. In addition, by rotating the second scanner motor (372a) forward / backward, the second reflective mirror (372a) may be oscillated in the X direction about the Y-direction axis, thereby vibrating the second beam (L2) in the X direction.

[0069] As an example, the scanner (370) may be driven to move the first beam (L1) and / or the second beam (L2) in the X direction based on the reference processing position, thereby adjusting the processing beam (L3) to have a processing width that matches the characteristics and processing target of the processing object (1). In this state, the processing object (1) may be moved multiple times in the Y direction to perform grooving or dicing processing.

[0070] Fig. 7 is a drawing illustrating an example of a process for adjusting a processing width by moving a first beam (L1) and / or a second beam (L2). In Fig. 7, the first beam (L1) and the second beam (L2) are illustrated in an oval shape, but this is merely a shape indicating the first and second beams (L1) (L2) and does not mean the actual shapes of the first and second beams (L1) (L2). In the case of grooving processing, the first and second beams (L1) (L2) may have a flat-top strength profile. Referring to Fig. 7, the first beam (L1) and the second beam (L2) may have a beam width (WL12) smaller than the target processing width (WL). In this case, the first beam (L1) or the second beam (L2) can be moved in a direction orthogonal to the processing direction, for example, in the X direction, so that the combined beam widths of the first beam (L1) and the second beam (L2) become the target processing width (WL). For example, the second beam (L2) is positioned at the reference processing position. In this state, the first scanner (371) can be driven to adjust the angle of the first reflection mirror (371a), thereby moving the first beam (L1) by, for example, OF (= WL-WL12) in the -X direction. In this state, the processing target (1) can be moved multiple times in the Y direction to perform grooving or dicing processing. In this way, by adjusting the degree of overlap between the first beam (L1) and the second beam (L2), a processing width (WL) larger than the beam widths (WL12) of the first beam (L1) and the second beam (L2) can be implemented. Although not shown in the drawing, the first beam (L1) may be positioned at the reference processing position and the second beam (L2) may be moved by OF in the +X direction, for example. In addition, the first beam (L1) and the second beam (L2) may be moved by OF / 2 in the -X direction and the +X direction, respectively, from the reference processing position. In this case, by applying the projection optical system (400) having the telecentric lens as described above, the moved first beam (L1) and / or second beam (L2) may be allowed to be incident perpendicularly on the processing surface of the processing target (1), thereby improving the processing quality.

[0071] Fig. 8 is a drawing showing an example of deterioration in processing quality due to a processing product. The processing beam (L3) is moved multiple times in the Y direction, which is the processing direction. At this time, the material (processing product) evaporated by the energy of the processing beam (L3) may adhere to the side walls (12) (13) of the groove (10) and solidify, thereby forming a recast layer (15) on the side walls (12) (13). Due to the recast layer (15), the side walls (12) (13) of the groove (10) may become uneven, making it difficult to obtain a groove (10) of high quality. The recast layer (15) may become the starting point of cracks due to stress unevenness. In addition, the processing product (16) may adhere to the outside of the groove (10), i.e., the surface of the processing target (1). Such adhered material is called a burr or debris. Burrs or debris may damage or contaminate circuit elements located adjacent to grooves (10) on the surface of the workpiece (1).

[0072] In addition, since the processing beam (L3) is repeatedly moved along the same path, high energy may be repeatedly concentrated at a specific location depending on the intensity profile of the processing beam (L3), which may cause a heat effected zone (HAZ) to be generated at that location.

[0073] Fig. 9 is a cross-sectional view showing an example of a laser processing process according to an embodiment of the laser processing device illustrated in Fig. 6. Fig. 10 is a plan view showing an example of a laser processing process according to an embodiment of the laser processing device illustrated in Fig. 6. In Figs. 9 and 10, the first beam (L1) and the second beam (L2) are illustrated in an oval shape, but this is only a shape indicating the first and second beams (L1) (L2), and does not mean the actual shapes of the first and second beams (L1) (L2). In the case of grooving processing, the first and second beams (L1) (L2) may have a flat-top type intensity profile.

[0074] As an example, the first beam (L1) and / or the second beam (L2) may be vibrated. For example, FIGS. 9 and 10 describe a case in which the first beam (L1) is moved (vibrated). Referring to FIGS. 9 and 10, the second beam (L2) having the beam width (WL12) is positioned at a reference processing position and is illustrated by a solid line. The first beam (L1) having the beam width (WL12) is vibrated in the X direction by, for example, a distance (WD) and is illustrated by a dotted line. While the processing object (1) is moved in the processing direction, i.e., the Y direction, the first scanner (371) is driven to vibrate the first beam (L1) in the X direction orthogonal to the processing direction. The processing object (1) may be moved multiple times in the Y direction to perform grooving or dicing processing. Depending on the scanning speed of the first scanner (371) and the movement speed of the processing object (1), the relative movement trajectory of the first beam (L1) with respect to the processing object (1) becomes a zigzag shape as illustrated in FIG. 10. The distance (WD) may be determined by taking into account the size of the area where recast and / or heat affected zone is expected to occur, taking into account the light intensity, processing speed, etc. of the first beam (L1) and the second beam (L2). For example, the distance (WD) may be set to be slightly larger than the size of the area where recast and / or heat affected zone (HAZ) is expected to occur. The distance (WD) may be adjusted, for example, by the rotation angle of the first scanner (371).

[0075] While the processing object (1) is moved multiple times in the Y direction, the recast layer (15) and the processing product (16) formed on the side wall (12) (13) and the surface of the groove (10) can be removed by the vibrating first beam (L1). In addition, since the first beam (L1) is vibrated, even if an intensity peak exists in the intensity profile of the first beam (L1), the portion corresponding to the intensity peak vibrates in the X direction, so that the peak energy is dispersed in the X direction, and the occurrence of a heat-affected zone can be reduced. In addition, the occurrence of the groove (14) shown in (a) of Fig. 3 can be reduced, so that the flatness of the bottom (11) of the groove (10) can be improved.

[0076] When the first beam (L1) and / or the second beam (L2) is vibrated, the first beam (L1) and / or the second beam (L2) is incident on the projection optical system (400) at an angle with respect to the optical axis of the projection optical system (400). Then, the first beam (L1) and / or the second beam (L2) that has passed through the projection optical system (400) can be incident on the processing surface of the processing object (1) at an angle. As described above, by applying a telecentric lens to the projection optical system (400), the vibrating first beam (L1) and / or the second beam (L2) can be incident perpendicularly on the processing surface of the processing object (1), thereby improving the processing quality.

[0077] Although not shown in the drawing, the first beam (L1) may be positioned at a reference processing position, and the second beam (L2) may vibrate in the X direction orthogonal to the processing direction. Of course, the first beam (L1) and the second beam (L2) may also vibrate in the X direction with respect to the reference processing position.

[0078] As an example, the machining width may be adjusted for each reference number of movements (one or more) in the Y direction. For example, the second beam (L2) may be positioned at a reference machining position, the first beam (L1) may be moved in the -X direction from the reference machining position, and the machining may be performed the reference number of times. Then, the first beam (L1) may be moved in the +X direction and the machining may be performed the reference number of times. This process may be repeated. In this way, the recast layer (15) and the machining product (16) may be removed. The occurrence of a heat-affected zone may be reduced, and the flatness of the floor (11) may be improved.

[0079] In the past, once the optical system of a laser processing device was set up, it was difficult to change processing conditions, etc. According to the present invention, without changing the optical system, the beam rotation angle (or the angle of the axis of reversal), the degree of overlap between two beams, the depth of focus between two beams, the polarization ratio of the laser beam before splitting, etc. can be adjusted according to the type of processing or the processing target, thereby realizing a laser processing device with a high degree of freedom and capable of various processing.

[0080] Hereinafter, embodiments of a laser processing method are described. Fig. 9 is a schematic flowchart of one embodiment of a laser processing method. Hereinafter, one embodiment of a laser processing method is described with reference to Figs. 1 and 10. Referring to FIG. 9, one embodiment of a laser processing method may include a step (S10) of splitting a laser beam (L) into first and second beams (L1) (L2), a step (S20) of changing a beam mode of at least one of the first and second beams (L1) (L2), a step (S30) of combining the first and second beams (L1) (L2), and a step (S40) of projecting the first and second beams (L1) (L2) onto a processing target (1). An unillustrated control unit controls a stage (100), a light source (200), a beam splitter (310), a beam converter (320), a beam combiner (330), and a projection optical system (400) to perform steps S10, S20, S30, and S40.

[0081] Referring to FIG. 1, one embodiment of a laser processing method for forming, for example, a groove in a processing target (1) according to the flow chart shown in FIG. 11 is described in detail.

[0082] [Step S10]

[0083] A laser beam (L) generated from a light source (200) is split into first and second beams (L1) (L2) having different polarization directions. For example, the light source (200) can generate a collimated laser beam (L). The laser beam (L) is reflected by a reflective mirror (361) and incident on a beam splitter (310). The beam splitter (310) can include, for example, a polarizing beam splitter having a polarizing surface (311). The beam splitter (310) splits the laser beam (L) into first and second beams (L1) (L2) having different polarization directions. When the laser beam (L) is incident on the beam splitter (310), the first polarization component of the laser beam (L), for example, the P-polarization component, passes through the polarization plane (311) and is emitted from the beam splitter (310) as the first beam (L1), and the second polarization component of the laser beam (L), for example, the S-polarization component, is reflected from the polarization plane (311) and is emitted from the beam splitter (310) as the second beam (L2).

[0084] [Step S20]

[0085] Next, at least one beam mode among the first and second beams (L1) (L2) is converted. Converting the beam mode means converting the input beam to an optical axis (Fig. 2: L axis ) can mean to rotate or flip around.

[0086] As an example, the beam mode of the second beam (L2) is converted using a beam converter (320) placed in the propagation path of the second beam (L2). The beam converter (320) converts the second beam (L2) along the optical axis (L axis ) can be rotated around the optical axis (L). The beam converter (320) rotates the second beam (L2) around the optical axis (L axis) can be inverted around the first beam (L1). However, the present invention is not limited thereto, and the beam converter (320) can be arranged in the propagation path of the first beam (L1) to convert the beam mode of the first beam (L1), and can also be arranged in the propagation paths of both the first and second beams (L1) (L2) to convert the beam modes of the first and second beams (L1) (L2). In the present embodiment, the beam converter (320) inverts the second beam (L2) in the X direction orthogonal to the processing direction. As a result, the intensity profile of the second beam (L2) becomes symmetrical with the intensity profile of the first beam (L1).

[0087] [Step S30]

[0088] Next, the first beam (L1) and the second beam (L2) are combined. The first beam (L1) passes through the reflection mirrors (365), (366), and (367) and is incident on the beam combiner (330). The second beam (L2), which has passed through the beam converter (320), passes through the reflection mirror (364) and is incident on the beam combiner (330). The beam combiner (330) combines, or in other words, overlaps, the first beam (L1) and the second beam (L2) to form a processed beam (L3). The beam combiner (330) may include, for example, a cube-type polarization beam combiner (PBC) having a polarization plane (331). The first beam (L1) passes through the polarization plane (331) of the beam combiner (330) and proceeds to the projection optical path, and the second beam (L2) is reflected by the polarization plane (311) of the beam combiner (330) and proceeds to the projection optical path. Accordingly, the first beam (L1) and the second beam (L2) are overlapped by the beam combiner (330) and are incident on the projection optical system (400) along the projection optical path as a processing beam (L3).

[0089] [Step S40]

[0090] Next, the processing beam (L3), i.e., the first beam (L1) and the second beam (L2), is projected onto the processing object (1) using the projection optical system (400). The projection optical system (400) focuses the processing beam (L3) onto the processing object (1). When dicing processing is performed, the processing beam (L3) may have a Gaussian intensity profile. When grooving processing is performed, a D-lens (diffraction lens) that converts the processing beam (L3) into a beam having a flat-top intensity profile may be included. The projection optical system (400) may include a telecentric lens for causing the processing beam (L3), i.e., the first and second beams (L1) (L2), to be incident perpendicularly onto the processing surface of the processing object (1).

[0091] With the processing beam (L3) focused on the processing target (1), the stage (100) is repeatedly moved multiple times in the Y direction, which is the processing direction. The processing target (1) is melted and vaporized by the energy of the processing beam (L3), so that the processing target (1) can be processed, for example, by grooving or dicing.

[0092] According to the laser processing method of the present embodiment, since the first beam (L1) and the second beam (L2) having mutually inverted intensity profiles are overlapped, the intensity profile of the processing beam (L3) can be symmetrical in the X direction orthogonal to the processing direction, and the unevenness of intensity along the X direction can be alleviated. The X-direction edges of the processing result can be processed symmetrically, and in the case of grooving processing, the flatness of the bottom (11) of the groove (10) can be improved. In addition, according to the laser processing method of the present embodiment, since the first and second beams (L1) (L2) having mutually orthogonal polarizations are combined and overlapped, interference between the first and second beams (L1) (L2) does not occur during the combining process. Therefore, deterioration of the processing quality due to interference during the combining process of the two beams can be prevented. As an example, the case where the second beam (L2) is inverted has been described, but the second beam (L2) may also be rotated. The rotation angle of the second beam (L2) can be determined so as to form a processing beam (L3) having optimal conditions depending on the shape of the intensity profile of the laser beam (L), the characteristics of the processing object (1), and the processing goal.

[0093] Fig. 12 is a schematic flowchart of one embodiment of a laser processing method. The laser processing method of this embodiment differs from the laser processing method of Fig. 11 in that it further comprises a step (S5) of adjusting the polarization characteristics of the laser beam (L). Therefore, the matters described with respect to Fig. 11 are equally applicable to Fig. 12, and the following description focuses on the differences.

[0094] [Step S5]

[0095] Referring to FIGS. 4 and 10, one embodiment of the laser processing method may include a step (S5) of adjusting the intensity ratio of the first and second beams (L1) (L2) by changing the polarization characteristics of the laser beam (L). Step (S5) is performed before separating the laser beam (L) into the first and second beams (L1) (L2), thereby adjusting the intensity ratio of the first and second beams (L1) (L2). As described above, the first and second beams (L1) (L2) have different polarization directions, that is, polarization directions that are orthogonal to each other. Therefore, by changing the polarization characteristics of the laser beam (L) to adjust the magnitudes of the two polarization components, the intensity ratio of the first and second beams (L1) (L2) after separation can be adjusted. As an example, the polarization characteristics of the laser beam (L) can be changed by rotating the half-wave plate (350) disposed between the light source (200) and the beam splitter (310), whereby the intensities of the P-polarization component and the S-polarization component of the laser beam (L) can be continuously adjusted. With this configuration, the intensities of the first and second beams (L1) (L2) can be adjusted so as to implement optimal processing quality according to the characteristics of the object to be processed (1), the processing goal, etc. In addition, the optimal processing beam (L3) can be easily formed while minimizing changes in the optical system, and a laser processing device having stable processing quality can be implemented.

[0096] Fig. 13 is a schematic flowchart of one embodiment of a laser processing method. The laser processing method of this embodiment differs from the embodiment of the laser processing method illustrated in Fig. 12 in that it further comprises a step (15) of adjusting the beam diameter of at least one of the first and second beams (L1, L2). Accordingly, the matters described with respect to Figs. 11 and 12 are equally applicable to Fig. 11, and the differences will be primarily described.

[0097] [Step S15]

[0098] Referring to FIGS. 5 and 13, the laser processing method of the present embodiment includes a step (S15) of adjusting the depth of focus by adjusting the beam diameter of at least one of the first and second beams (L1) (L2). Step (S15) may be performed before step (S20). For example, the beam diameters of the first and second beams (L1) (L2) may be adjusted using first and second beam expanders (341) (342), each of which includes one or more zoom lenses. As a result, the depth of focus of the first beam (L1) and the depth of focus of the second beam (L2) become different, so that the depth of focus (DOF) of the processing beam (L3) formed by overlapping the first and second beams (L1) (L2) may be expanded. Accordingly, processing that is less sensitive to the flatness of the processing target (1) is possible, and stable processing quality can be achieved even if the flatness of the processing target (1) is partially uneven. In addition, in the case of grooving processing, the depth of focus of the processing beam (L3) can be made relatively shallow, and in the case of dicing processing, the depth of focus of the processing beam (L3) can be made relatively deep, so that the processing target can be effectively responded to.

[0099] Fig. 14 is a schematic flowchart of one embodiment of a laser processing method. The laser processing method of this embodiment differs from the embodiment of the laser processing method illustrated in Fig. 11 in that it further comprises a step (25) of moving (vibrating) at least one of the first and second beams (L1, L2). Accordingly, the matters described with respect to Figs. 11 to 13 are equally applicable to Fig. 14, and the differences will be primarily described.

[0100] [Step S25]

[0101] Referring to FIGS. 6 and 14, the laser processing method of the present embodiment includes a step (S25) of vibrating at least one of the first and second beams (L1) (L2). For example, while the object to be processed (1) is moved in the processing direction, i.e., the Y direction, at least one of the first beam (L1) and the second beam (L2) can be vibrated in a direction orthogonal to the processing direction, i.e., the X direction, using a scanner (370). The width of the vibration can be appropriately adjusted depending on the characteristics of the object to be processed (1), the processing target, the processing state, etc.

[0102] For example, the second beam (L2) can be positioned at a reference processing position, and the first beam (L1) can be moved (vibrated) in the X direction orthogonal to the processing direction based on the reference processing position. For example, the first beam (L1) can be positioned at a reference processing position, and the second beam (L2) can be moved (vibrated) in the X direction orthogonal to the processing direction based on the reference processing position. For example, the first and second beams (L1)(L2) can be moved (vibrated) in the X direction orthogonal to the processing direction based on the reference processing position. By moving at least one of the first beam (L1) and the second beam (L2) in the X direction to adjust the overlapping width of the first beam (L1) and the second beam (L2), grooving or dicing processing having a target processing width larger than the beam widths of the first beam (L1) and the second beam (L2) is possible. In addition, the side walls (12) (13) and the recast layer (15) (16) formed on the surface of the groove (10) can be removed by the vibrating first beam (L1) and / or second beam (L2). Even if an intensity peak exists in the intensity profile of the first beam (L1) and / or second beam (L2), since the portion corresponding to the intensity peak vibrates in the X direction, the peak energy is dispersed in the X direction, so that the occurrence of a heat-affected zone can be reduced, the occurrence of a groove (14) can be reduced, and the flatness of the bottom (11) of the groove (10) can be improved.

[0103] In addition, when a projection optical system (400) equipped with a telecentric lens is employed, the vibrating first beam (L1) and / or second beam (L2) can be incident perpendicularly to the processing surface of the processing object (1), thereby improving the processing quality.

[0104] Although embodiments of the present invention have been described above, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible.

Claims

1. Light source; A beam splitter that separates a laser beam from the light source into a first beam having a first polarization and a second beam having a second polarization; A beam converter that changes the beam mode of at least one of the first beam and the second beam; A beam combiner that overlaps the first beam and the second beam with the same optical path; A laser processing device including a projection optical system that projects the superimposed first beam and second beam onto a processing target.

2. In paragraph 1, The above beam splitter is a laser processing device including a polarizing beam splitter.

3. In paragraph 1, A laser processing device in which the beam converter rotates or reverses at least one of the first beam and the second beam so that the first beam and the second beam have different intensity profiles.

4. In paragraph 3, The beam converter is a laser processing device that rotates at least one of the first beam and the second beam around an optical axis.

5. In paragraph 4, The above beam converter The above beam converter is a laser processing device including a dove prism.

6. In paragraph 5, A laser processing device capable of adjusting the rotation angle of at least one of the first beam and the second beam by rotating the dove prism.

7. In paragraph 3, The beam converter is a laser processing device that reverses at least one of the first beam and the second beam.

8. In paragraph 1, A laser processing device comprising a beam diameter controller that adjusts the depth of focus of at least one of the first beam and the second beam by adjusting the beam diameter of at least one of the first beam and the second beam.

9. In paragraph 1, A laser processing device comprising a beam intensity controller arranged between the light source and the beam splitter to change the polarization characteristics of the laser beam, thereby controlling the intensities of the first beam and the second beam.

10. In paragraph 1, A laser processing device comprising at least one scanner for moving at least one of the first and second beams in a direction orthogonal to the processing direction.

11. In paragraph 10, A laser processing device that processes the processing object while moving at least one of the first beam and the second beam in a direction orthogonal to the processing direction.

12. In paragraph 10, A laser processing device that processes the object to be processed while moving at least one of the first beam and the second beam in a direction orthogonal to the processing direction.

13. In paragraph 1, A laser processing device including a telecentric lens that irradiates a beam parallel to the optical axis to the processing target regardless of the incident angles of the first beam and the second beam.

Images