Laser processing method and laser processing apparatus

Abstract

A disclosed laser processing method comprises the steps of: performing primary processing while positioning a processing beam having a first processing width smaller than a target width of a groove at a first position inside the target width and relatively moving the processing beam with respect to an object to be processed; and alternately performing a plurality of secondary processing and tertiary processing in which the processing is performed while sequentially positioning the processing beam at a plurality of second positions moved by a first step in a first direction with respect to the first position and at a plurality of third positions moved by a second step in an opposite direction of the second position with respect to the first position and relatively moving the processing beam in a second direction with respect to the object to be processed.

Description

Laser processing method and laser processing device

[0001] The present disclosure relates to a laser processing method and apparatus, and more specifically, to a laser processing method and apparatus for forming a groove in a workpiece.

[0002] In semiconductor manufacturing processes, glass substrates, silicon substrates, sapphire substrates, etc., are used as wafers. To individually separate multiple circuit elements formed on the wafer during the preparation stage for the semiconductor process or after the semiconductor process is completed, it is necessary to cut the wafer.

[0003] As a cutting method, there is a mechanical cutting method that uses a rotating saw blade to cut the wafer. In the case of the mechanical cutting method, there is a risk that circuit components on the wafer may be damaged by debris generated during the cutting process. Furthermore, the mechanical cutting method has disadvantages, such as a very slow processing speed and the cost and time required to replace saw blades due to wear. Additionally, microcracks may occur near the cutting line.

[0004] As a cutting method using a laser, there is laser full cutting, which completely cuts the wafer. Laser full cutting is difficult to apply when the wafer thickness is thick, and is applied to cutting wafers with a thickness of less than 50㎛.

[0005] As a composite cutting method, a method has been devised in which a groove is formed on a wafer using a laser, and then the wafer is completely cut using a rotary saw blade.

[0006] A laser processing method and apparatus capable of forming high-quality grooves on a workpiece are provided.

[0007] A laser processing method according to one aspect of the present disclosure is a laser processing method for forming a groove having a target width on a workpiece, comprising: a step of preparing a processing beam having a first processing width smaller than the target width; a step of performing a first processing by positioning the processing beam at a first position inside the target width and moving the processing beam relative to the workpiece in a second direction intersecting the first direction in the width direction; a step of performing a plurality of second processing by positioning the processing beam at a plurality of second positions moved by a first step in the first direction relative to the first position and performing processing by moving the processing beam relative to the workpiece in the second direction, and a step of performing a plurality of third processing by positioning the processing beam at a plurality of third positions moved by a second step opposite to the first position and performing processing by moving the processing beam relative to the workpiece in the second direction.

[0008] In one embodiment, the first position may be a position where the center of the processing beam and the center of the groove coincide.

[0009] In one embodiment, the first position may be a position in which the center of the processing beam is deviated in the first direction from the center of the groove.

[0010] In one embodiment, the first processing width may be 70% or more of the target width of the groove. In one embodiment, the first processing width may be 80% or more of the target width of the groove.

[0011] As one embodiment, the processing depth by the first processing may be 10% to 30% of the target depth of the groove.

[0012] As an example, the processing depth of each of the plurality of secondary and tertiary processing steps may be smaller than the processing depth of the primary processing step.

[0013] In one embodiment, the plurality of second positions and the plurality of third positions may be symmetric with respect to the first position.

[0014] In one embodiment, the plurality of second positions and the plurality of third positions may be asymmetric with respect to the first position.

[0015] As an example, when the second processing and the third processing are repeated multiple times, the number of relative movements of the processing beam in the second direction may be smaller in the later processing stage compared to the earlier processing stage.

[0016] As an embodiment, the method may further include the step of preparing a processing beam having a second processing width greater than the target width; and the step of aligning the center of the processing beam with the center of the groove and performing a fourth processing while moving the processing beam relative to the workpiece.

[0017] A laser processing device according to one aspect of the present disclosure comprises: a stage on which a workpiece is mounted; a laser generator for generating a laser beam; a beam shaper for shaping the laser beam into a flat-top processing beam; and a focusing optical system for focusing the processing beam onto the workpiece. A control unit for controlling the stage, the laser generator, the beam shaper, and the focusing optical system to form a groove having a target width on the workpiece; wherein the control unit alternately performs a first processing step in which a processing beam having a first processing width smaller than the target width is positioned at a first position inside the target width and the processing beam is moved relative to the workpiece in a second direction intersecting the first direction which is the width direction, thereby performing a first processing step in which the processing beam is positioned at a plurality of second positions moved by a first step in the first direction relative to the first position and the processing beam is moved relative to the workpiece in the second direction, thereby performing a plurality of second processing steps in which the processing beam is positioned at a plurality of third positions moved by a second step opposite to the second position relative to the first position and the processing beam is moved relative to the workpiece in the second direction, and the processing beam is positioned at a plurality of third positions moved by a second step relative to the first position and the processing beam is moved relative to the workpiece in the second direction, thereby performing a third processing step in which the processing beam is positioned at a plurality of third positions moved by a second step opposite to the second position relative to the first position and the processing beam is moved relative to the workpiece in the second direction. Controls the light-gathering optical system.

[0018] In one embodiment, the first position may be a position where the center of the processing beam and the center of the groove coincide.

[0019] In one embodiment, the first position may be a position in which the center of the processing beam is deviated in the first direction from the center of the groove.

[0020] As one embodiment, the processing width may be 70% or more of the target width of the groove.

[0021] As one embodiment, the processing depth by the first processing may be 10% to 30% of the target depth of the groove.

[0022] As an example, the processing depth of each of the plurality of secondary and tertiary processing steps may be smaller than the processing depth of the primary processing step.

[0023] In one embodiment, the plurality of second positions and the plurality of third positions may be symmetric with respect to the first position.

[0024] In one embodiment, the plurality of second positions and the plurality of third positions may be asymmetric with respect to the first position.

[0025] In one embodiment, the control unit can control the stage, the laser generator, the beam shaper, and the focusing optical system to prepare a processing beam having a second processing width greater than the target width, align the center of the processing beam with the center of the groove, and perform a fourth processing while moving the processing beam relative to the workpiece.

[0026] According to embodiments of the laser processing method and apparatus of the present disclosure, a processing beam having a small processing width is moved stepwise in a first direction (the width direction of the groove) to form a groove having a target width and a target length, so that processing products such as burrs, debris, and recast layers can be removed during the processing process.

[0027] In addition, the energy of the processing beam can be dispersed so that it is not concentrated in a specific area of ​​the groove bottom, thereby mitigating the formation of wedge-shaped grooves and improving the flatness of the groove bottom.

[0028] According to embodiments of the laser processing method and apparatus of the present disclosure, grooves having various widths can be formed without changing the configuration of the optical system of the laser processing apparatus.

[0029] FIG. 1 is a schematic diagram of a laser processing device according to one embodiment of the present disclosure.

[0030] FIG. 2 is a schematic plan view of one embodiment of a workpiece with a groove formed therein.

[0031] FIG. 3 is a schematic cross-sectional view of one embodiment of a workpiece with a groove formed therein.

[0032] Figure 4 is a cross-sectional view showing a groove formed on a workpiece by a conventional processing method.

[0033] Figure 5 is a schematic flowchart of one embodiment of a laser processing method.

[0034] FIGS. 6a to 6e are drawings showing an embodiment of a laser processing method.

[0035] Figure 7 is a flowchart showing one embodiment of a laser processing method.

[0036] FIG. 8 is a cross-sectional view showing one embodiment of a laser processing method.

[0037] Hereinafter, embodiments of a laser processing method and apparatus according to the present disclosure will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals refer to the same components, and the size or thickness of each component may be exaggerated for clarity of explanation.

[0038] FIG. 1 is a schematic diagram of a laser processing device according to one embodiment of the present disclosure. FIG. 2 is a schematic plan view of one embodiment of a workpiece (1) having a groove (2) formed therein. FIG. 3 is a schematic cross-sectional view of one embodiment of a workpiece (1) having a groove (2) formed therein. Referring to FIG. 1, the laser processing device may comprise a stage (100), a laser generator (200), a beam shaper (300), a focusing optical system (400), and a control unit (500).

[0039] A workpiece (1) is mounted on a stage (100). The workpiece (1) may be a wafer used in a semiconductor process, such as a glass substrate, a silicon substrate, or a sapphire substrate. The workpiece (1) may be a wafer before the semiconductor process is performed. As shown in FIG. 2, the workpiece (1) may be a wafer on which a plurality of circuit elements (11) are formed on the surface by a series of semiconductor processes. Although not shown in the drawings, a fixing means for fixing the workpiece (1) to the stage (100) may be provided. For example, the fixing means may be a vacuum chuck.

[0040] The stage (100) may be moved laterally, for example, in the X direction, or in the Y direction, or in both the X and Y directions, by means of a moving means not shown. Additionally, the stage (100) may be moved in the Z direction perpendicular to the X and Y directions. Additionally, the stage (100) may be rotated about the Z direction as an axis. For example, the stage (100) may be moved in the Y direction to form a groove (2) that extends in the Y direction. Then, the stage (100) may be rotated 90 degrees with respect to the Z direction and the stage (100) may be moved in the Y direction to form a groove (2) that extends in the X direction.

[0041] The laser generator (200) generates a laser beam (L1). The laser beam (L1) may be, for example, collimated parallel light. The laser beam (L1) may be an ultrashort pulse laser beam having a pulse width of 1 μs or less, for example, a pulse width of the nanosecond order, picosecond order, or femtosecond order. For example, the peak power density of the laser beam (L1) having a pulse width of the femtosecond order is 1×10⁻⁶ 8It can be greater than (W / cm²), and the peak power density of the laser beam can be lower than this, with a pulse width of the nanosecond or picosecond order. Such a laser beam (L1) has very high focusing ability and can be focused down to the diffraction limit.

[0042] The beam shaper (300) shapes the laser beam (L1) so that it has a power profile suitable for processing. The laser beam (L1) may have, for example, a Gaussian power profile. The beam shaper (300) can shape the laser beam (L1) into a processing beam (L2) having a flat-top power profile.

[0043] The focusing optical system (400) focuses the processing beam (L2) onto the workpiece (1). The focusing optical system (400) may include a focusing lens. The focusing optical system (400) may also be equipped with a zoom lens unit for adjusting the size of the processing beam (L2), for example, the processing width.

[0044] The control unit (500) controls the stage (100), laser generator (200), beam shaper (300), and focusing optical system (400) to form a groove (2) having a target width (Fig. 3: W2) on the workpiece (1). The control unit (500) may be equipped with, for example, a processor, memory, and input means. A control program for controlling the laser processing device may be stored in the memory. A processing command including various parameters for forming the groove (2) may be input through the input means. The processor may control the laser processing device to form the groove (2) by driving the control program stored in the memory. The input means may be, for example, a host computer connected to the laser processing device, or it may be an input means such as a keyboard provided on the laser processing device itself.

[0045] When a processing beam (L2) is focused onto a workpiece (1), it is compressed temporally and spatially near the point of focus, forming a state in which very high peak power is concentrated locally. Then, the workpiece (1) is locally melted and evaporated by the energy of the processing beam (L2). For example, the position of the workpiece (1) in a first direction (e.g., X direction) is fixed so that the processing beam (L2) is positioned at a location where a groove (2) is to be formed on the workpiece (1), and the processing beam (L2) is moved relative to the workpiece (1) multiple times in a second direction (e.g., Y direction) to form a groove (2) that extends in the Y direction. For example, the Y-direction position of the workpiece (1) can be fixed so that the processing beam (L2) is positioned at the location where the groove (2) is to be formed on the workpiece (1), and the processing beam (L2) can be moved relative to the workpiece (1) multiple times in the X-direction to form a groove (2) that extends in the X-direction. The relative movement of the processing beam (L2) in the X-direction or Y-direction with respect to the workpiece (1) can be implemented, for example, by moving the stage (100) on which the workpiece (1) is mounted in the X-direction or Y-direction. Of course, the workpiece (1) may be positioned at a fixed location and the processing beam (L2) may be moved in the X-direction or Y-direction. In this case, an optical system including a beam shaper (300) and a focusing optical system (400) may be moved in the X-direction or Y-direction. Below, an exemplary case is described in which the lateral (Y-direction) position of the processing beam (L2) is fixed and the stage (100) is driven in the lateral direction to move the workpiece (1).

[0046] FIG. 4 is a cross-sectional view showing a groove (2') formed on a workpiece (1') by a conventional processing method. Referring to FIG. 4, the processing width (WL') of the processing beam (L2') is the same as the target width (W2') of the groove (2'). The processing beam (L2') is reciprocated multiple times, for example, in the Y direction. In this way, according to a laser processing method in which the processing width (WL') of the processing beam (L2') is the same as the target width (W2') of the groove (2'), various processing defects may occur.

[0047] For example, as the processing beam (L2') reciprocates multiple times in the Y direction, the energy of the processing beam (L2') may be concentrated near the edge of the processing beam (L2') of the workpiece (1'), causing it to be processed excessively compared to other parts. As a result, a wedge-shaped groove may be formed from the bottom (21') of the groove (2') near the side wall (22') of the groove (2'), as indicated by reference numeral 26' in FIG. 4. A crack may occur from the wedge-shaped groove (26'). If the crack progresses to the lower surface of the workpiece (1'), the workpiece (1') may be damaged. If the crack moves in an undesirable direction, for example, a circuit element (Fig. 2: 11) formed on the surface (23') of the workpiece (1') may be damaged.

[0048] Additionally, the material (processing product) evaporated by the energy of the processing beam (L2') may adhere to and solidify on the sidewall (22') of the groove (2'), thereby forming a recast layer (27') on the sidewall (22'). Due to the recast layer (27'), it is difficult to form a groove (2') with a target width (W2'). Furthermore, the sidewall (22') of the groove (2') becomes uneven, making it difficult to obtain a high-quality groove (2'). The recast layer (27') can become the starting point for cracks caused by stress unevenness.

[0049] Additionally, as indicated by reference numeral 28' in FIG. 4, the processing product may be attached to the outside of the groove (2'), that is, to the surface (23') of the workpiece (1'). Such attached material (28') is called a burr or debris. The burr or debris may damage or contaminate a circuit element (Fig. 2: 11) located adjacent to the groove (2') on the surface (23') of the workpiece (1').

[0050] The various processing defects mentioned above can become more severe as the depth of the groove increases. Recently, there has been a growing demand for processing grooves with a depth of 50㎛ or more, and there is a need for laser processing methods and devices that can reduce processing defects and form high-quality grooves.

[0051] Taking these points into account, the laser processing apparatus and method according to the present disclosure utilize a processing beam (L2) having a first processing width (WL) smaller than the target width (W2) of the groove (2), as illustrated in FIG. 3. The processing beam (L2) is moved stepwise to a plurality of positions in the width direction of the groove (2), for example, in the first direction (X direction), and at each of the plurality of positions, the processing beam (L2) is moved relative to the workpiece (1), for example, in the second direction (Y direction) to form the groove (2). The groove (2) may be defined, for example, by a bottom (21) immersed from the surface (23) of the workpiece (1) and a side wall (22) extending from the bottom (21) toward the surface (23). The groove (2) may be in a shape that extends in the transverse direction, for example, in the second direction. For example, the side wall (22) may be perpendicular to the surface (23) and may be an inclined surface that widens outward from the bottom (21) toward the surface (23).

[0052] In FIG. 3, the processing beam (L2) is shown in an elliptical shape, but this is merely a shape to represent the processing beam (L2) and does not represent the actual shape of the processing beam (L2). As previously mentioned, the processing beam (L2) may have a flat-top energy profile.

[0053] As described above, if the same location is continuously processed with a processing beam (L2') having non-uniform strength, a wedge-shaped groove may be formed along the edge of the bottom (21') of the groove (2'). Additionally, the flatness of the bottom (21') of the groove (21') may be reduced. The laser processing apparatus and method according to the present disclosure can improve the flatness of the bottom by forming a groove having a target width while gradually expanding the processing width through stepwise movement of the processing beam in a first direction.

[0054] Hereinafter, embodiments of a laser processing method are described. FIG. 5 is a schematic flowchart of one embodiment of a laser processing method. Referring to FIG. 5, one embodiment of a laser processing method may include the step of preparing a processing beam (L2) having a first processing width (WL) (S10), the step of positioning the processing beam (L2) at a first position and performing a first processing step (S20), the step of positioning the processing beam (L2) at a second position and performing a second processing step (S30), the step of positioning the processing beam (L2) at a third position and performing a third processing step (S40), and the step of alternately performing the second processing and the third processing multiple times, for example, n times (S50).

[0055] The control unit (500) controls the stage (100), laser generator (200), beam shaper (300), and focusing optical system (400) to perform steps S10, S20, S30, S40, and S50. For example, the control unit (500) controls the stage (100), laser generator (200), beam shaper (300), and focusing optical system (400) to prepare a processing beam (L2) having a first processing width (WL) (S10), perform a first processing (S20), and alternately repeat a second processing (S30) and a third processing (S40) (S50). The first processing step is performed by positioning a processing beam (L2) having a first processing width (WL) smaller than the target width (W2) at a first position inside the target width (W2), and moving the processing beam (L2) relative to the workpiece (1) in a second direction (Y) that intersects, for example, the first direction (X) in the width direction. The second processing step is performed by positioning the processing beam (L2) at a plurality of second positions that are moved by a first step (ST1) in the first direction (X) relative to the first position, and moving the processing beam (L2) relative to the workpiece (1) in a second direction (Y). The third processing step is performed by positioning the processing beam (L2) at a plurality of third positions that are moved by a second step (ST2) opposite to the second position relative to the first position, and moving the processing beam (L2) relative to the workpiece (1) in a second direction (Y). Secondary and tertiary processing are performed alternately.

[0056] FIGS. 6a to 6e are drawings showing an embodiment of a laser processing method. With reference to FIGS. 6a to 6e, an embodiment of a laser processing method for forming a groove (2) having a target width (W2) on a workpiece (1) according to the flowchart shown in FIG. 5 will be described in detail. In FIGS. 6a to 6e, the processing beam (L2) is shown in an elliptical shape, but this is merely a shape to indicate the processing beam (L2) and does not represent the actual shape of the processing beam (L2). As previously mentioned, the processing beam (L2) may have a flat-top energy profile.

[0057]

[0058] [Step S10]

[0059] A processing beam (L2) having a first processing width (WL) smaller than the target width (W2) of the groove (2) is prepared. For example, the control unit (500) can drive the beam shaper (300) and / or the focusing optical system (400) to adjust the processing width of the processing beam (L2) to the first processing width (WL).

[0060] Referring to FIG. 6a, the first machining width (WL) is smaller than the target width (W2) of the groove (2). In FIG. 6a, the groove (2) to be finally formed is shown by a dashed line at two points. The first machining width (WL) may be 70% or more of the target width (W2). If the first machining width (WL) is smaller than 70% of the target width (W2), the number of repetitions (n) of the secondary and tertiary machining described later may increase, and the machining time may be extended. For example, the first machining width (WL) may be 80% or more of the target width (W2).

[0061]

[0062] [Step S20]

[0063] A processing beam (L2) is positioned at a first position that is inside the target width (W2), and a first processing step is performed by moving the processing beam (L2) relative to the workpiece (1) in a second direction (Y) that is orthogonal to the first direction (X), which is the width direction. First, the processing beam (L2) is positioned at the first position. The first position is inside the target width (W2) of the groove (2) to be finally formed. In other words, the first position is a position where the processing beam (L2) does not overlap with the side walls (22) of the width direction of the groove (2), that is, the first direction (X). For example, as shown in FIG. 6a, the first position may be a position where the center of the processing beam (L2) coincides with the centerline (CL) of the first direction (X) of the groove (2). However, the scope of the invention is not limited by this, and the first position may be a position offset to either side of the first direction (X) with respect to the centerline (CL), as long as the processing beam (L2) does not overlap with the side walls (22) of the width direction of the groove (2), i.e., the first direction (X). The control unit (500) can drive the stage (100) to move the workpiece (1) in the first direction (X) and position the processing beam (L2) at the first position.

[0064] Next, primary processing is performed. Primary processing is performed by irradiating the workpiece (1) with a processing beam (L2) and moving it relative to the workpiece (1) in a second direction (Y). For example, the processing beam (L2) can be fixed at a first position, and the stage (100) can be moved back and forth multiple times in the second direction (Y). As the material constituting the workpiece (1) is melted and evaporated by the energy of the processing beam (L2), a primary groove is formed as indicated by reference numeral 2-1 in FIG. 6a.

[0065] A recast layer (27-1) may be created on the side wall (22-1) of the primary groove (2-1) created by the primary processing. A processing product (28-1), such as burrs or debris, may be created on the surface (23) of the workpiece (1). Additionally, a wedge-shaped groove (29-1) immersed from the bottom (21-1) may be created at a location adjacent to the side wall (22-1) within the bottom (21-1) of the primary groove (2-1). The recast layer (27-1), the processing product (28-1), and the groove (29-1) may be removed by the secondary processing and tertiary processing described later.

[0066] The machining depth (D11) of the first machining may be 10% to 30% of the target depth (D2) of the groove (2). If the machining depth of the first machining is greater than 30% of the target depth (D2), the amount of recast layer (27-1) increases, and even if the second and third machining described later is performed, the recast layer (27-1) may not be sufficiently removed. In addition, the depth of the groove (29-1) may become excessively deep. If the machining depth of the first machining is less than 10% of the target depth (D2), the number of second and third machining steps described later becomes too high, and the machining speed may decrease.

[0067] The recast layer (27-1), processed product (28-1), etc., must be removed before they are completely hardened to ensure high removal efficiency. Therefore, the number of first, second, and third processing steps can be determined so that second and third processing steps can be performed before the recast layer (27-1) and processed product (28-1) from the first processing step solidify.

[0068]

[0069] [Step S30]

[0070] When the first processing is completed, the second processing is performed. As illustrated in FIG. 6b, the second processing can be performed by moving the processing beam (L2) to a second position and moving the processing beam (L2) relative to the workpiece (1) in the second direction (Y). In the case of the first second processing, the second position is a position moved by one step (ST1) in the first direction (X) from the first position, for example, in the +X direction. In the case of the second processing after the second, the second position is a position moved by one step (ST1) in the +X direction from the previous second position. When the processing beam (L2) is positioned at the second position, the side wall (22-a1) corresponding to the second position of the first groove (2-1) is positioned within the projection area of ​​the processing beam (L2). The first step (ST1) can be determined to satisfy these conditions.

[0071] Secondary processing is performed by irradiating the workpiece (1) with respect to the workpiece (1) and moving the workpiece (1) relative to the workpiece (1) in a second direction (Y). For example, the workpiece (L2) can be fixed at a second position, and the stage (100) can be moved back and forth multiple times in the second direction (Y). As the material constituting the workpiece (1) is melted and evaporated by the energy of the workpiece (L2), a secondary groove is formed as indicated by reference numeral 2-2 in FIG. 6b. The processing depth (D21) of the secondary groove (2-2) may be smaller than the processing depth (D11) of the primary processing. To this end, the number of relative movements of the workpiece (L2) in the second direction during secondary processing may be smaller than during primary processing. By doing so, the formation of a recast layer, a processed product, and a groove can be reduced during secondary processing.

[0072] In the process of forming a secondary groove (2-2) by secondary processing, the recast layer (27-1) on the side wall (22-1a) of the primary groove (2-1) and the processed product (28-1) adjacent to the side wall (22-1a) of the primary groove (2-1) on the surface (23) of the workpiece (1) can be removed. Additionally, the groove (29-1) adjacent to the side wall (22-1a) of the primary groove (2-1) can be removed.

[0073]

[0074] [Step S40]

[0075] When the second processing is finished, the third processing is performed. The third processing can be performed by moving the processing beam (L2) to a third position as shown in FIG. 6c and moving the processing beam (L2) relative to the workpiece (1) in the second direction (Y). In the case of the first third processing, the third position is a position moved by two steps (ST2) from the first position in the first direction (X) in the opposite direction of the second position, for example, in the -X direction. In the case of the third processing after the second, the third position is a position moved by two steps (ST2) in the -X direction from the previous third position. When the processing beam (L2) is positioned at the third position, the side wall (22-1b) corresponding to the third position of the first groove (2-1) is positioned within the projection area of ​​the processing beam (L2). The second step (ST2) can be determined to satisfy these conditions. Step 1 (ST1) and Step 2 (ST2) may be the same or different.

[0076] The third processing is performed by irradiating the workpiece (1) with respect to the workpiece (1) and moving the workpiece (1) relative to the workpiece (1) in a second direction (Y). For example, the workpiece (L2) can be fixed at a third position, and the stage (100) can be moved back and forth multiple times in the second direction (Y). As the material constituting the workpiece (1) is melted and evaporated by the energy of the workpiece (L2), a third groove is formed as indicated by reference numeral 2-3 in FIG. 6c. The processing depth (D31) of the third groove (2-3) may be smaller than the processing depth (D11) of the first processing. To this end, the number of relative movements of the workpiece (L2) in the second direction during the third processing may be smaller than during the first processing. By doing so, the formation of the recast layer, processing product, and groove can be reduced during the third processing.

[0077] In the process of forming the third groove (2-3) by the third processing, the recast layer (27-1) on the side wall (22-1b) of the first groove (2-1) and the processed product (28-1) adjacent to the side wall (22-1b) of the first groove (2-1) on the surface of the workpiece (1) can be removed. Additionally, the groove (29-1) adjacent to the side wall (22-1b) of the first groove (2-1) can be removed.

[0078]

[0079] [Step S50]

[0080] Secondary processing and tertiary processing are performed sequentially, for example, n times. Referring to FIG. 6d, the positions of the processing beam (L2) in the primary processing and multiple secondary and tertiary processing steps are schematically illustrated. FIG. 6d illustrates a case where the secondary processing and tertiary processing steps are repeated three times, but the number of repetitions is not limited to this, and the number of repetitions for the secondary processing and tertiary processing steps can be appropriately selected to form a groove (2) having a target width (W2) and a target depth (D2). As described above, in the secondary processing step after the second step, the second position is a position moved by one step (ST1) from the previous second position, and in the tertiary processing step after the second step, the third position is a position moved by two steps (ST2) from the previous third position.

[0081] By repeating the second and third processing steps, the depth of the groove gradually increases, and the width of the groove gradually increases. By performing the second and third processing steps n times, for example, a groove (2) having a target width (W2) and a target depth (D2) can be formed as shown in FIG. 3. Since the recast layer, processing product, and wedge-shaped groove generated during the preceding second and third processing steps are removed by the subsequent processing steps, a high-quality groove (2) with improved flatness of the bottom (21) can be reliably formed.

[0082] The machining depth by the second machining (Fig. 6b: D21) and the machining depth by the third machining (Fig. 6c: D31) are smaller than the machining depth by the first machining (Fig. 6a: D11). For example, the number of reciprocating movements in the second direction (Y) in each of the second and third machining processes is smaller than the number of reciprocating movements in the second direction (Y) in the first machining process. As a result, the formation of recast layers and machining products can be reduced during the second and third machining processes. In addition, wedge-shaped grooves can also be minimized.

[0083] When repeating the second and third processing n times, the number of reciprocating movements of the processing beam (L2) in the second direction (Y) may be smaller in the later processing stage compared to the earlier processing stage. For example, as the processing stage progresses, the number of reciprocating movements of the processing beam (L2) in the second direction (Y) may gradually decrease. By doing so, the formation of recast layers, processing products, and wedge-shaped grooves can be reduced. However, this is not limited thereto, and when repeating the second and third processing n times, the number of relative movements of the processing beam (L2) in the second direction (Y) may be the same.

[0084] In one embodiment, as illustrated in FIG. 6d, the second position and the third position may be symmetric with respect to the centerline (CL) of the groove (2). In other words, the center of the processing beam (L2) in the first processing coincides with the centerline (CL) of the groove (2). Additionally, a plurality of second processing is performed at a plurality of second positions, and a plurality of third processing is performed at a plurality of third positions, wherein the paired second and third positions may be symmetric with respect to the first position. That is, the paired second and third positions may be symmetric with respect to the centerline (CL) of the groove (2). In this case, the first step (ST1) and the second step (ST2) are identical. A plurality of first steps (ST1) may be identical, and a plurality of second steps (ST2) may also be identical. However, this is not limited thereto. If the condition that the paired first step (ST1) and second step (ST2) are identical is satisfied, at least one of the plurality of first steps (ST1) may be different from the remaining first steps (ST1), and at least one of the plurality of second steps (ST2) may be different from the remaining second steps (ST2).

[0085] As an example of one embodiment, as shown in FIG. 6e, the second position and the third position may be asymmetric with respect to the centerline (CL) of the groove (2). In the first processing step, the first position of the processing beam (L2) may be a position deviated in the first direction (X) from the centerline (CL) of the groove (2). For example, the first position may be a position deviated by an offset amount (OS1) in the +X direction from the centerline (CL) of the groove (2). In this case, the second position and the third position of the first step are positions moved by the first step (ST1) and the second step (ST2), respectively, from the first position. The second position and the third position from the second step to the nth step are positions moved by the first step (ST1) and the second step (ST2), respectively, from the previous second position and third position. In order to form a groove (2) having a target width (W2) and a target depth (D2) by repeating the secondary processing and the tertiary processing n times each, the first step (ST1) and the second step (ST2) are different from each other. In FIG. 6e, the second step (ST2) is larger than the first step (ST1). Multiple secondary processing is performed at multiple second positions, and multiple tertiary processing is performed at multiple third positions, wherein the paired second and third positions are asymmetric with respect to the first position. Multiple first steps (ST1) may be identical, and multiple second steps (ST2) may be identical. At least one of the multiple first steps (ST1) may be different from the remaining first steps (ST1). Of course, at least one of the multiple second steps (ST2) may be different from the remaining second steps (ST2). However, the scope of the invention is not limited by this.

[0086] According to the embodiments of the laser processing method and apparatus described above, the following effects can be obtained.

[0087] First, in the case of a conventional processing method in which the position of a processing beam having a processing width equal to the target width of the groove to be formed is fixed in a first direction and processing is performed all at once to the target depth, there is a possibility of wafer breakage, contamination, or damage to circuit components due to the generation of a large amount of recast layers and processing products, and the formation of deep wedge-shaped grooves. According to the laser processing method and apparatus of the present disclosure, a groove having a target width and target length is formed by moving a processing beam having a small processing width stepwise in a first direction. Accordingly, processing products such as burrs and debris, and recast layers, etc., can be removed during the processing process. In addition, since the energy of the processing beam can be dispersed so as not to be concentrated in a specific area of ​​the bottom of the groove, the generation of wedge-shaped grooves can be mitigated and the overall flatness of the bottom of the groove can be improved. Therefore, a high-quality groove can be formed.

[0088] Second, since the processing beam is moved stepwise to multiple second and third positions, grooves of various widths can be formed without changing the configuration of the optical system of the laser processing device. For example, when the configuration of the optical system of the laser processing device is configured to form a groove with a width of 90 μm, it is possible to form a groove with a width of 90 μm or more by increasing the number of repetitions of the second processing and third processing.

[0089] FIG. 7 is a flowchart showing an embodiment of a laser processing method. FIG. 8 is a cross-sectional view showing an embodiment of a laser processing method. A control unit (500) can control a stage (100), a laser generator (200), a beam shaper (300), and a focusing optical system (400) to perform step S60 after performing steps S10, S20, S30, S40, and S50. With reference to FIG. 8, an embodiment of a laser processing method for forming a groove (2) having a target width (W2) on a workpiece (1) according to the flowchart shown in FIG. 7 is described.

[0090] Steps S10 to S50 in FIG. 7 are the same as described with reference to FIG. 5 and FIG. 6a to 6e. After step S50 is completed, as shown in FIG. 8, there may be a processing product (28), such as a burr or debris, at a location adjacent to the side wall (22) of the groove (2) on the surface (23) of the workpiece (1). A laser processing method according to one embodiment of the present disclosure may further comprise a fourth processing step for removing the processing product (28).

[0091]

[0092] [Step S60]

[0093] A processing beam (L2) having a second processing width (WL2) that is larger than the target width (W2) is prepared. For example, the control unit (500) can drive the beam shaper (300) and / or the focusing optical system (400) to adjust the processing width of the processing beam (L2) to the second processing width (WL2). Referring to FIG. 8, the second processing width (WL2) is larger than the target width (W2) of the groove (2) and can be set to a value sufficient to remove the processing product (28). For example, the second processing width (WL2) may be about 110% of the target width (W2).

[0094]

[0095] [Step S70]

[0096] Next, a fourth processing step is performed. First, the processing beam (L2) is positioned at a fourth position. The fourth position may be, for example, a position where the processing beam (L2) coincides with the center of the groove (2). The control unit (500) can drive the stage (100) to move the workpiece (1) in the first direction (X) to position the processing beam (L2) at the fourth position. Next, the processing beam (L2) is irradiated onto the workpiece (1) and moved relative to the workpiece (1) in the second direction (Y). For example, the control unit (500) can fix the position of the processing beam (L2) and move the stage (100) back and forth multiple times in the second direction (Y). The processing product (28) present on the surface (23) of the workpiece (1) can be removed by the energy of the processing beam (L2). By doing so, a high-quality groove (2) can be formed on the workpiece (1).

[0097] Although embodiments of the present invention have been described above, they are merely illustrative and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom.

Claims

1. A laser processing method for forming a groove having a target width on a workpiece, A step of preparing a processing beam having a first processing width smaller than the above target width; A step of positioning the processing beam at a first position inside the target width, and performing a first processing step while moving the processing beam relative to the workpiece in a second direction intersecting the first direction, which is the width direction; A laser processing method comprising the step of alternately performing a plurality of secondary processing, wherein the processing beam is positioned at a plurality of second positions moved by a first step in the first direction relative to a first position and processing is performed while moving the processing beam relative to the workpiece in the second direction, and a plurality of tertiary processing, wherein the processing beam is positioned at a plurality of third positions moved by a second step opposite to the second position relative to the first position and processing is performed while moving the processing beam relative to the workpiece in the second direction.

2. In Paragraph 1, A laser processing method in which the first position is a position where the center of the processing beam and the center of the groove coincide.

3. In Paragraph 1, A laser processing method in which the first position is a position in which the center of the processing beam is deviated in the first direction from the center of the groove.

4. In Paragraph 1, A laser processing method in which the first processing width is at least 70% of the target width of the groove.

5. In Paragraph 4, A laser processing method in which the first processing width is at least 80% of the target width of the groove.

6. In Paragraph 1, A laser processing method in which the processing depth by the above primary processing is 10% to 30% of the target depth of the above groove.

7. In Paragraph 1, A laser processing method in which the processing depth of each of the plurality of secondary and tertiary processing steps is smaller than the processing depth of the primary processing step.

8. In Paragraph 1, A laser processing method in which the plurality of second positions and the plurality of third positions are symmetric with respect to the first position.

9. In Paragraph 1, A laser processing method in which the plurality of second positions and the plurality of third positions are asymmetric with respect to the first position.

10. In Paragraph 1, A laser processing method in which, when the above-mentioned second processing and the above-mentioned third processing are repeated multiple times, the number of relative movements of the processing beam in the above-mentioned second direction is smaller in the later stages of processing compared to the earlier stages of processing.

11. In Paragraph 1, A step of preparing a processing beam having a second processing width greater than the above target width; A laser processing method further comprising the step of aligning the center of the processing beam with the center of the groove and performing a fourth processing while moving the processing beam relative to the workpiece.

12. A stage on which a workpiece is mounted; A laser generator that generates a laser beam; A beam shaping machine that shapes the above laser beam into a flat-top processing beam; A focusing optical system for focusing the above processing beam onto the above processing target; A control unit that controls the stage, the laser generator, the beam shaper, and the focusing optical system to form a groove having a target width on the workpiece; The above control unit is, A processing beam having a first processing width smaller than the above target width is positioned at a first position inside the above target width, and a first processing is performed while moving the processing beam relative to the workpiece in a second direction intersecting the first direction, which is the width direction. Alternately performing a plurality of secondary processing steps, wherein the processing beam is positioned at a plurality of second positions moved by a first step in the first direction relative to the first position and processing is performed while moving the processing beam relatively in the second direction relative to the workpiece, and a plurality of tertiary processing steps, wherein the processing beam is positioned at a plurality of third positions moved by a second step in the opposite direction of the second position relative to the first position and processing is performed while moving the processing beam relatively in the second direction relative to the workpiece. A laser processing device that controls the above stage, the above laser generator, the above beam shaper, and the above focusing optical system.

13. In Paragraph 12, A laser processing device in which the first position is a position where the center of the processing beam and the center of the groove coincide.

14. In Paragraph 12, A laser processing device in which the first position is a position in which the center of the processing beam is deviated in the first direction from the center of the groove.

15. In Paragraph 12, A laser processing device in which the processing width is at least 70% of the target width of the groove.

16. In Paragraph 12, A laser processing device in which the processing depth by the above primary processing is 10% to 30% of the target depth of the above groove.

17. In Paragraph 12, A laser processing device in which the processing depth of each of the plurality of secondary and tertiary processing steps is smaller than the processing depth of the primary processing step.

18. In Paragraph 12, A laser processing device in which the plurality of second positions and the plurality of third positions are symmetric with respect to the first position.

19. In Paragraph 12, A laser processing device in which the plurality of second positions and the plurality of third positions are asymmetric with respect to the first position.

20. In Paragraph 12, The above control unit is, Prepare a processing beam having a second processing width greater than the above target width, and Align the center of the processing beam with the center of the groove, and perform a fourth processing step while moving the processing beam relative to the workpiece. A laser processing device that controls the above stage, the above laser generator, the above beam shaper, and the above focusing optical system.

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