Laser processing method

Abstract

To provide a laser processing method in which the problem that cracking of about dozens μm occurs radially in a crossover point at which a first direction crosses a second direction, which deteriorates a quality of a member formed of a work-piece can be solved.SOLUTION: The laser processing method comprises: a first processing step of applying processing for forming a division starting point or a division groove by emitting a laser beam in a first direction to form a first processing mark; and a second processing step of applying processing for forming a division starting point or a division groove by emitting a laser beam in a second direction crossing the first direction, so as to form a second processing mark, which further comprises an unprocessed area processing step of forming an unprocessed area to which processing is not applied, in a crossover point at which the first direction crosses the second direction and of processing the unprocessed area, in the first processing step or in the second processing step. The unprocessed area processing step applies processing of emitting a laser beam in a direction inclined with respect to the first direction or the second direction to form the division starting point or the division groove, so as to form a connection processing mark connecting the first processing mark to the second processing mark.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a laser processing method for irradiating a plate-shaped workpiece with a laser beam to perform processing.

Background Art

[0002] A wafer on which a plurality of devices such as ICs and LSIs are partitioned by a dicing line and formed on the surface is processed on the dicing line by a laser processing apparatus and divided into individual device chips, which are used in electric devices such as mobile phones and personal computers.

[0003] Laser processing apparatuses include those of a type that form a modified layer by positioning the focal point of a laser beam having a wavelength that is transmissive to the wafer inside the wafer and irradiating it (see, for example, Patent Document 1), those of a type that form a shield tunnel formed from pores and a modified layer surrounding the pores by positioning the focal point of a laser beam having a wavelength that is transmissive to the wafer at a required position on the wafer and irradiating it (see, for example, Patent Document 2), and those of a type that form a groove by ablation processing by positioning the focal point of a laser beam having a wavelength that is absorptive to the wafer at a required position on the wafer and irradiating it (see, for example, Patent Document 3), and are appropriately selected according to the workpiece including the wafer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

特許文献2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, due to the wafer material and the direction of the crystal orientation, when processing is performed by irradiating the planned division lines with a laser beam, cracks of several tens of micrometers in size occur radially in unintended directions at the intersections of orthogonal planned division lines, which degrades the quality of the device chip.

[0006] In particular, if the crystal orientation and the direction of the planned division line are misaligned, cracks may occur in unintended directions different from the planned division line, leading to a decrease in the quality of the device chip. Similarly, in the technology of laser processing to form a desired shape from a plate-like workpiece such as silicon (Si) or silicon carbide (SiC), cracks may occur in unintended directions at intersections, resulting in the same problems as described above.

[0007] The present invention has been made in view of the above facts, and its main technical problem is to provide a laser processing method that solves the problem of radial cracks of several tens of micrometers occurring at the intersection where a first direction and a second direction intersect to form a dividing point or dividing groove in a plate-shaped workpiece by laser processing, thereby degrading the quality of the component formed from the workpiece. [Means for solving the problem]

[0008] To solve the above-mentioned main technical problems, the present invention provides a laser processing method for processing a plate-shaped workpiece by irradiating it with a laser beam, comprising: a first processing step of irradiating a laser beam in a first direction to form a starting point for division or a division groove and thereby forming a first processing mark; and a second processing step of irradiating a laser beam in a second direction intersecting the first direction to form a starting point for division or a division groove and thereby forming a second processing mark, wherein in the first processing step or the second processing step, at the intersection where the first direction and the second direction intersect, an unprocessed area is formed and the unprocessed area is further processed, wherein the unprocessed area processing step involves irradiating a laser beam in a direction inclined with respect to the first direction or the second direction to form a starting point for division or a division groove and thereby forming the first processing mark and Applicable Form a connecting machining mark that links the second machining mark. The process involves using the end of the second processing mark along the second direction on one side of the unprocessed region as the base end, and irradiating it with a laser beam at an angle between it and the first direction, so as not to be perpendicular to the first direction, to form a connecting processing mark that connects the first processing mark and the second processing mark, which are made of a modified layer, and further, using the end of the second processing mark along the second direction on the other side of the unprocessed region as the base end, irradiating it with a laser beam at an angle between it and the first direction, so as not to be perpendicular to the first direction, and A laser beam is irradiated to form a connecting mark that connects the first processed mark and the second processed mark, which are made of a modified layer, and the angle of inclination of each connecting mark, or the position of the end that serves as the base when forming each connecting mark, is appropriately adjusted so that the connecting mark formed with the end of the second processed mark on one side of the unprocessed area as the base end, and the connecting mark formed with the end of the second processed mark on the other side of the unprocessed area as the base end, are not connected at the same location in the first processed mark. A laser processing method is provided.

[0009] The first and second processing marks may be modified layers formed by irradiating the workpiece with a laser beam of a wavelength that is transparent to the workpiece, with the focal point positioned inside the workpiece. Alternatively, the first and second processing marks may be shield tunnels formed from pores and a modified layer surrounding the pores by irradiating the workpiece with a laser beam of a wavelength that is transparent to the workpiece, with the focal point positioned at a required location on the workpiece. Furthermore, the first and second processing marks may be grooves formed by ablation by irradiating the workpiece with a laser beam of a wavelength that is absorbent to the workpiece, with the focal point positioned at a required location on the workpiece.

[0010] The plate-shaped workpiece is a wafer on which multiple devices are partitioned by dividing lines and formed on its surface, and it is preferable that the first direction and the second direction are the directions of the dividing lines. The plate-shaped workpiece may also be a Si wafer or a GaAs wafer in which the crystal orientation and the first direction and the second direction are tilted by 45 degrees, and the plate-shaped workpiece may also be a hexagonal wafer which is a SiC wafer, an LT wafer, or an SiO2 wafer. [Effects of the Invention]

[0011] The laser processing method of the present invention comprises: a first processing step of irradiating a laser beam in a first direction to form a starting point for division or a division groove to form a first processing mark; and a second processing step of irradiating a laser beam in a second direction intersecting the first direction to form a starting point for division or a division groove to form a second processing mark, wherein in the first processing step or the second processing step, at the intersection where the first direction and the second direction intersect, an unprocessed area is formed and the unprocessed area is processed, wherein the unprocessed area processing step involves irradiating a laser beam in a direction inclined with respect to the first direction or the second direction to form a starting point for division or a division groove to form the first processing mark and Applicable Form a connecting machining mark that links the second machining mark. The process involves using the end of the second processing mark along the second direction on one side of the unprocessed region as the base end, and irradiating it with a laser beam at an angle between it and the first direction, so as not to be perpendicular to the first direction, to form a connecting processing mark that connects the first processing mark and the second processing mark, which are made of a modified layer, and further, using the end of the second processing mark along the second direction on the other side of the unprocessed region as the base end, irradiating it with a laser beam at an angle between it and the first direction, so as not to be perpendicular to the first direction, and A laser beam is irradiated to form a connecting mark that connects the first processed mark and the second processed mark, which are made of a modified layer, and the angle of inclination of each connecting mark, or the position of the end that serves as the base when forming each connecting mark, is appropriately adjusted so that the connecting mark formed with the end of the second processed mark on one side of the unprocessed area as the base end, and the connecting mark formed with the end of the second processed mark on the other side of the unprocessed area as the base end, are not connected at the same location in the first processed mark. Therefore, at the intersection where the first direction and the second direction intersect to form the starting point or division groove of a plate-shaped workpiece by laser processing, the first processing mark and the second processing mark do not intersect at the intersection. As a result, the problem of radial cracks of several tens of micrometers occurring at the intersection and degrading the quality of the component formed from the workpiece is resolved. [Brief explanation of the drawing]

[0012] [Figure 1] This is an overall perspective view of the laser processing equipment. [Figure 2] Figure 1 is a perspective view showing how the first processing step is carried out using the laser processing apparatus shown. [Figure 3] (a) A plan view showing an enlarged portion of the embodiment shown in Figure 2, and (b) A plan view showing an enlarged portion of the embodiment in which the second processing step is carried out. [Figure 4] This is a plan view showing how the processing step for the unprocessed area is carried out. [Figure 5] (a) A plan view showing another embodiment of the first processing step, and (b) A plan view showing another embodiment of the second processing step. [Figure 6]It is a plan view showing another embodiment of the unprocessed area processing step. [Figure 7] (a) A perspective view showing an embodiment different from the embodiment of the laser processing method shown in FIGS. 2 to 6, and (b) a plan view showing an enlarged area A of (a).

Embodiments for Carrying out the Invention

[0013] Hereinafter, embodiments of a laser processing method configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0014] FIG. 1 shows an overall perspective view of a laser processing apparatus 1 suitable for carrying out the laser processing method of the present embodiment. The laser processing apparatus 1 is disposed on a base 2 and includes at least a holding means 3 for holding a plate-like workpiece described later, a laser beam irradiating means 4 for irradiating the workpiece held by the holding means 3 with a laser beam, and a control means 20.

[0015] Further, the laser processing apparatus 1 includes an imaging means 5 for performing an alignment for detecting a processing position by imaging the workpiece held by the holding means 3, and a processing feed means 6 for relatively moving the holding means 3 and the laser beam irradiating means 4.

[0016] The holding means 3 is a means for holding a plate-shaped workpiece. As shown in FIG. 1, it includes a rectangular X-axis direction movable plate 31 mounted on the base 2 so as to be movable in the X-axis direction, a rectangular Y-axis direction movable plate 32 mounted on the X-axis direction movable plate 31 so as to be movable in the Y-axis direction, a cylindrical support column 33 fixed to the upper surface of the Y-axis direction movable plate 32, and a rectangular cover plate 34 fixed to the upper end of the support column 33. A chuck table 35 extending upward through a long hole formed on the cover plate 34 is disposed on the cover plate 34. The chuck table 35 is configured to be rotatable by a rotation driving means (not shown) housed in the support column 33. On the upper surface of the chuck table 35, a circular suction chuck 36 formed of a porous material having air permeability and having an XY plane specified by X coordinates and Y coordinates as a holding surface is disposed. The suction chuck 36 is connected to a suction means (not shown) by a flow path passing through the support column 33. Around the suction chuck 36, four clamps 37 used when holding the workpiece described later on the chuck table 35 are arranged at equal intervals. By operating the suction means, the workpiece can be sucked and held by the suction chuck 36.

[0017] The machining feed means 6 includes an X-axis moving means 61 for moving the holding means 3 in the X-axis direction and a Y-axis moving means 62 for moving the holding means 3 in the Y-axis direction. The X-axis moving means 61 converts the rotational motion of a motor 63 into a linear motion via a ball screw 64 and transmits it to the X-axis direction movable plate 31, and moves the X-axis direction movable plate 31 in the X-axis direction along a pair of guide rails 2a, 2a arranged along the X-axis direction on the base 2. The Y-axis moving means 62 converts the rotational motion of a motor 65 into a linear motion via a ball screw 66 and transmits it to the Y-axis direction movable plate 32, and moves the Y-axis direction movable plate 32 in the Y-axis direction along a pair of guide rails 31a, 31a arranged along the Y-axis direction on the X-axis direction movable plate 31.

[0018] The laser processing apparatus 1 includes a frame 7 consisting of a vertical wall portion 7a erected to the side of the X-axis moving means 61 and Y-axis moving means 62 on a base 2, and a horizontal wall portion 7b extending horizontally from the upper end of the vertical wall portion 7a. The optical system constituting the laser beam irradiation means 4 and the imaging means 5 are housed inside the horizontal wall portion 7b of the frame 7. Details are omitted, but the optical system of the laser beam irradiation means 4 includes an oscillator that emits a laser beam LB of a desired wavelength, an attenuator that adjusts the output of the laser beam LB emitted from the oscillator, a reflective mirror that converts the optical path of the laser beam LB toward the concentrator 41 equipped with a concentrating lens (not shown), etc. The control means 20 controls the laser beam irradiation means 4 to adjust the repetition frequency, spot diameter, average output, etc.

[0019] The control means 20 is composed of a computer and includes a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) for storing the control program and the like, a read-write random access memory (RAM) for temporarily storing detected values, calculation results, etc., and input and output interfaces (details are not shown in the illustration). In addition to the laser beam irradiation means 4 described above, the control means 20 is connected to and controlled by an imaging means 5, an X-axis moving means 61, a Y-axis moving means 62, etc., and the information of the position to be processed, which is captured and detected by the imaging means 5, is stored in an appropriate memory.

[0020] The laser processing apparatus 1 described above has a configuration that is generally as described above, and the laser processing method of this embodiment, which is carried out using the laser processing apparatus 1, will be described below.

[0021] The plate-shaped workpiece processed by the laser processing method of this embodiment is a silicon (Si) wafer 10, as shown in Figure 2, in which multiple devices 12 are demarcated by division lines 14 and formed on the surface 10a. The wafer 10 is supported by a protective tape T on a frame F having an opening Fa capable of housing the wafer 10. The division lines 14 include a plurality of first division lines 14a along a predetermined first direction R1 on the wafer 10, and a plurality of second division lines 14b along a second direction R2 perpendicular to the first direction R1. The surface 10a of the wafer 10 is demarcated in a grid pattern by the first division lines 14a and the second division lines 14b. A notch 16 for specifying the crystal orientation is formed on the outer edge of the wafer 10 in this embodiment. In this embodiment, as shown in Figure 3(a), the crystal orientation D is tilted at a 45-degree angle in plan view with respect to the first planned division line 14a and the second planned division line 14b.

[0022] The wafer 10 described above is attracted to the chuck table 35 of the holding means 3 described above, and the frame F is gripped and fixed by the clamp 37. Next, the X-axis moving means 61 and the Y-axis moving means 62 are operated to position the wafer 10 directly below the imaging means 5, the wafer 10 is photographed by the imaging means 5, and alignment is performed to detect the positions of the first division line 14a along the first direction R1 and the second division line 14b along the second direction R2 perpendicular to the first direction R1 in XY coordinates. Furthermore, the direction of the first division line 14a is aligned in the X-axis direction, and the second division line 14b is aligned in the Y-axis direction.

[0023] Next, based on the position information detected by the imaging means 5 described above, the light condenser 41 of the laser beam irradiation means 4 is positioned directly above the processing start position of a predetermined first division line 14a along the first direction R1, and the focal point of a laser beam LB1 with a wavelength that is transparent to the wafer 10 is positioned and irradiated into the wafer 10, and the wafer 10 is processed and fed in the X-axis direction to form a first processing mark 100 consisting of a modified layer that will serve as the starting point for division, along the predetermined first division line 14a of the wafer 10, as shown in Figure 3(a). Once the first processing mark 100 has been formed, the wafer 10 is indexed and fed in the Y-axis direction by the distance between adjacent first division lines 14a, so that the unprocessed first division line 14a is positioned directly below the light condenser 41. Then, in the same manner as described above, the focal point of the laser beam LB1 is positioned inside the first division line 14a and irradiated, and the wafer 10 is processed and fed in the X-axis direction to form a first processing mark 100 consisting of the same modified layer as described above. Similarly, the wafer 10 is processed and fed in the X-axis direction and the Y-axis direction to form a first processing mark 100 in the same manner as described above along all of the first division lines 14a along the first direction R1, and the first processing step is completed.

[0024] In this embodiment, the processing to form the modified layer is carried out under the following laser processing conditions. The first processing mark 100 is formed by repeatedly irradiating the area 2 to 3 times while changing the depth at which the focal point is positioned within the same first planned division line 14a. The second processing step and the unprocessed area processing step, which will be described later, are also carried out under the same laser processing conditions as shown below. Wavelength: 1064nm Repetition frequency: 100kHz Spot diameter: 1 μm Irradiation interval: 5μm Average output: 0.5W

[0025] Once the first processing step is complete, the wafer 10 is rotated 90 degrees together with the chuck table 35 to align the unprocessed second division line 14b along the second direction R2 with the X-axis direction, as shown in Figure 3(b). Then, the focuser 41 of the laser beam irradiation means 4 is positioned at the processing start position of the predetermined second division line 14b, and the focus point of the laser beam LB1 is positioned inside the second division line 14b and irradiated, while the wafer 10 is processed and fed in the X-axis direction to form a second processing mark 110 consisting of a modified layer that serves as the starting point for division, along the predetermined second division line 14b of the wafer 10, as shown in Figure 3(b).

[0026] In this embodiment, as shown in the figure, when forming the second processing mark 110, at the intersection where the first division line 14a along the first direction R1 and the second division line 14b along the second direction R2 intersect, an unprocessed area S1 is formed between the ends 110a and 110b that straddle the intersection. Once the second processing mark 110 including the unprocessed area S1 has been formed on the second division line 14b in this manner, the focusing point of the laser beam LB1 is positioned inside and irradiated onto all remaining second division lines 14b in the same manner as described above, to form a second processing mark 110 with an unprocessed area S1 at the intersection where the first division line 14a and the second division line 14b intersect, thereby completing the second processing step.

[0027] In the embodiment described above, the second processing mark 110 formed in the second processing step has an unprocessed area S1 at the intersection where the first planned division line 14a and the second planned division line 14b intersect, whereas the first processing mark 100 formed in the first processing step is also formed at this intersection. However, the present invention is not limited thereto. For example, when forming the first processing mark 100 in the first processing step, an unprocessed area S1 is formed at the intersection where the laser beam LB1 is not irradiated, and when forming the second processing mark 110 in the second processing step, the second processing mark 110 is formed at this intersection.

[0028] In the embodiment described above, if an unprocessed area S1 is formed in the second processing step at the intersection where the first planned division line 14a and the second planned division line 14b intersect, and the laser beam LB1 is not irradiated there, then the unprocessed area processing step described below is performed to process the unprocessed area S1.

[0029] When performing the unprocessed area processing step, the chuck table 35 is rotated 90 degrees to align the first planned division line 14a along the first direction R1 with the X-axis direction, as shown in Figure 4(a). Then, the laser beam irradiation means 4, the X-axis moving means 61, and the Y-axis moving means 62 are operated to irradiate the laser beam LB1 with the end 110a of the second processed mark 110 formed on the second planned division line 14b along the second direction R2 as the base end, at an angle such that it is not perpendicular to the first direction R1 and an obtuse angle is formed between it and the first direction R1 towards the device 12, as shown in the figure, thereby forming connecting processed marks 120a and 120b that connect the first processed mark 100 and the second processed mark 110, which are made of the same modified layer as the first processed mark 100 and the second processed mark 110.

[0030] As described above, once the connecting processing marks 120a and 120b are formed, then, as shown in Figure 4(b), the end 110b of the lower second processing mark 110 is used as the base, and the laser beam LB1 is irradiated with an inclination such that it is not perpendicular to the first direction R1 and an obtuse angle is formed between it and the first direction R1 towards the device 12, thereby forming connecting processing marks 122a and 122b made of the same modified layer as described above. At this time, the inclination angle of each connecting processing mark, or the position of the base end 110a and 110b when forming each connecting processing mark, is appropriately adjusted so that the above connecting processing marks 120a and 120b and the connecting processing marks 122a and 122b are not connected at the same location on the first planned division line 14a. The above unprocessed area processing steps are then performed, and the laser processing method of the present invention is completed.

[0031] If the laser processing method of this embodiment described above is carried out, the wafer 10 is transported to a splitting device (not shown), and external force is applied to the wafer 10, such as by expanding it in the planar direction, to split it starting from the first processing mark 110, the second processing mark 120, and the connecting processing marks 120a, 120b, 122a, and 122b, thereby dividing the wafer 10 into individual devices 12.

[0032] In the raw area processing step described with reference to Figure 4, an example was described in which the raw area S1 is formed at an intersection where devices 12 are present above and below the first planned division line 14a, and devices 12 are present on both sides of the second planned division line 14b, that is, at an intersection surrounded by four devices 12, and four connecting processing marks 120a, 120b, 122a, and 122b are formed to connect the first processing mark 100 and the second processing mark 110. However, the present invention is not limited to this, and for example, in Figure 4(a), if the device 12 is not formed below the first planned division line 14a, but only above the first planned division line 14a, on both sides of the second planned division line 14b, then only the above connecting processing marks 120a and 120b need to be formed at the intersection where the raw area S1 is formed, then only the above connecting processing marks 120a and 120b need to be formed. In other words, the raw area processing step in this embodiment only needs to form a connecting processing mark that links the first processing mark 100 and the second processing mark 110 only on the side where the device 12 is formed.

[0033] According to the laser processing method of this embodiment described above, the first processing mark 100 formed on the first division line 14a along the first direction R1 and the second processing mark 110 formed on the second division line 14b along the second direction R2 perpendicular to the first direction R1 are connected by a connecting processing mark in an inclined direction. Therefore, since the first processing mark 100 and the second processing mark 110 do not intersect at the intersection where the first division line 14a and the second division line 14b intersect, the problem of radial cracks of several tens of micrometers occurring at the intersection of the first division line 14a and the second division line 14b, thereby degrading the quality of the individually divided devices 12, is resolved.

[0034] The present invention is not limited to the embodiments described above, and may also be a laser processing method according to other embodiments as shown in Figures 5 and 6. First, similar to the embodiments described above, the wafer 10 is attracted to the chuck table 35 of the holding means 3 of the laser processing apparatus 1 described with reference to Figure 1, and the frame F is gripped and fixed by the clamp 37. Next, the X-axis moving means 61 and the Y-axis moving means 62 are operated to position the wafer 10 directly below the imaging means 5, and the wafer 10 is photographed by the imaging means 5. The positions of the first planned division line 14a along the first direction R1 and the second planned division line 14b along the second direction R2 perpendicular to the first direction R1 are detected in XY coordinates, and the direction of the first planned division line 14a is aligned in the X-axis direction, and the second planned division line 14b is aligned in the Y-axis direction.

[0035] Next, based on the position information detected by the imaging means 5 described above, the light concentrator 41 of the laser beam irradiation means 4 is positioned directly above the processing start position of a predetermined first division line 14a along the first direction R1. Then, the focal point of the laser beam LB1 is positioned inside the wafer 10 and irradiated, and the wafer 10 is processed and fed in the X-axis direction to form a first processing mark 130 consisting of a modified layer that serves as the starting point for division, along the predetermined first division line 14a of the wafer 10, as shown in Figure 5(a). In this embodiment, when forming the first processing mark 130, an unprocessed area S2 is formed between the ends 130a and 130b that straddle the intersection where the first division line 14a along the first direction R1 and the second division line 14b along the second direction R2 intersect. In this way, once a first processed mark 130 including an unprocessed area S2 is formed on the first planned division line 14a, the same method is used to position the focal point of the laser beam LB1 inside and irradiate all remaining first planned division lines 14a along the first direction R1, thereby forming a first processed mark 130 with an unprocessed area S2 at the intersection where the first planned division line 14a and the second planned division line 14b intersect, and completing the first processing step.

[0036] Once the first processing step described above is completed, the wafer 10 is rotated 90 degrees together with the chuck table 35 to align the unprocessed second division line 14b along the second direction R2 in the X-axis direction and the first division line 14a in the Y-axis direction, as shown in Figure 5(b). Then, the focuser 41 of the laser beam irradiation means 4 is positioned at the processing start position of the predetermined second division line 14b, and the focus point of the laser beam LB1 is positioned inside the second division line 14b and irradiated, while the wafer 10 is processed and fed in the X-axis direction to form a second processing mark 140 consisting of a modified layer that serves as the starting point for division, along the predetermined second division line 14b of the wafer 10, as shown in Figure 5(b).

[0037] In this embodiment, as shown in the figure, when forming the second processing mark 140, the laser beam LB1 is not irradiated between the ends 140a and 140b that sandwich the previously formed unprocessed region S2. In this way, once the second processing mark 140 has been formed on the second division line 14b, excluding the unprocessed region S2, the second processing mark 140 is formed on all remaining second division lines 14b by positioning the focal point of the laser beam LB1 inside and irradiating them in the same manner as described above, thereby completing the second processing step. In this embodiment, as shown in Figure 5(b), an unprocessed region S2 is formed at the intersection where the first division line 14a and the second division line 14b intersect, where neither the first processing mark 130 nor the second processing mark 140 is formed.

[0038] As described above, after performing the first and second processing steps to form the first processing marks 130 and the second processing marks 140, and after forming an unprocessed area S2 at the intersection where the first planned division line 14a and the second planned division line 14b intersect, the unprocessed area processing step described below is performed to process the unprocessed area S2.

[0039] When performing the processing step for the unprocessed area, the chuck table 35 is rotated 90 degrees to align the first planned division line 14a along the first direction R1 with the X-axis direction, as shown in Figure 6(a). Then, the laser beam irradiation means 4, the X-axis moving means 61, and the Y-axis moving means 62 are operated to irradiate the laser beam LB1 with an inclination such that it is not perpendicular to the first direction R1 and an obtuse angle is formed on the device 12 side, as shown in the figure, thereby performing processing to form a modified layer and creating connecting processing marks 150a and 150b that connect the ends 130a and 130b of the first processing marks 130 along the first direction R1 and the end 140a of the second processing marks 140 along the second direction R2.

[0040] As described above, once the connecting processing marks 150a and 150b are formed, the laser beam irradiation means 4, X-axis moving means 61, and Y-axis moving means 62 are then operated to irradiate the laser beam LB1 with an inclination such that it is not perpendicular to the first direction R1 and an obtuse angle is formed towards the device 12, as shown in Figure 6(b), thereby forming a modified layer and creating connecting processing marks 152a and 152b that connect the first processing mark 130 along the first direction R1 and the end 140b of the second processing mark 140 along the second direction R2. At this time, the inclination angle of each connecting processing mark, or the position when each connecting processing mark is formed, is appropriately adjusted so that the above-mentioned connecting processing marks 150a and 150b and the connecting processing marks 152a and 152b are not connected at the same location on the first planned division line 14a. With the above, the unprocessed area processing step is executed and the laser processing method of the present invention is completed.

[0041] If the laser processing method of this embodiment described above is carried out, the wafer 10 is transported to a splitting device (not shown), and external force is applied by expanding the wafer 10, etc., so that the first processing mark 130, the second processing mark 140, and the connecting processing marks 150a, 150b, 152a, and 152b function as starting points for splitting, the wafer 10 can be split into individual devices 12, and the same effects as in the embodiment described above can be obtained.

[0042] Furthermore, the plate-shaped workpiece processed by the laser processing method of the present invention is not limited to a wafer 10 in which the above-described plurality of devices 12 are partitioned by division lines 14 and formed on the surface 10a. For example, it is also applicable to laser processing of a wafer 10' as shown in Figure 7 to divide it into a desired shape, for example, a substantially rectangular plate-shaped member 11A and an annular member 11B.

[0043] The wafer 10' shown in Figure 7 is, for example, a silicon (Si) plate-shaped wafer. The laser processing apparatus 1 described above irradiates the wafer 10' with a laser beam LB2 of an absorbent wavelength, and the laser processing method described below is carried out.

[0044] The wafer 10' shown in Figure 7 is supported by a protective tape T on an annular frame F. A notch 16' for identifying the crystal orientation is formed on the outer edge of the wafer 10'. When carrying out the laser processing method of this embodiment, first, the wafer 10' is attracted to the chuck table 35 of the holding means 3 of the laser processing apparatus 1, and the frame F is gripped and fixed by the clamp 37. Next, the X-axis moving means 61 and Y-axis moving means 62 are operated to position the wafer 10' directly below the imaging means 5, and the imaging means 5 is used to take an image and perform alignment to detect the position on the wafer 10' to be laser processed.

[0045] The control means 20 has the shape of the rectangular plate-like member 11A described above stored in it, and separates it from the wafer 10' to produce the product. When executing the laser processing method of this embodiment, the XY coordinates of the short sides 160, 160 are set to align with the first direction R1 based on the stored information regarding the shape of the plate-like member 11A, and the XY coordinates of the long sides 170, 170 are set to align with the second direction R2 which is perpendicular to the first direction R1. Then, the chuck table 35 is rotated to align the direction of the short sides 160 with the X-axis direction and the direction of the long sides 170 with the Y-axis direction.

[0046] Next, based on the position information detected by the imaging means 5 described above, the light concentrator 41 of the laser beam irradiation means 4 is positioned directly above the processing start position of the short side 160 along the first direction R1, and the focal point of the laser beam LB2, which has a wavelength absorbed by the wafer 10', is positioned on the surface 10a' of the wafer 10', and the wafer 10 is processed and fed in the X-axis direction to form a first processing mark which will be a dividing groove along the short sides 160, 160 along the first direction R1 of the wafer 10', as shown in Figure 7(a). When irradiating with the laser beam LB2 under the laser processing conditions of this embodiment, the irradiation of the laser beam LB2 is repeated about 10 times along the same line to form a dividing groove that penetrates to the back side of the wafer 10'. The first processing step is completed by forming the first processing mark consisting of the dividing groove along the short sides 160, 160 as described above.

[0047] The laser processing performed in this embodiment is carried out, for example, under the following laser processing conditions. Wavelength: 355nm Repetition frequency: 100kHz Spot diameter: 10 μm Irradiation interval: 0.5μm Average output: 3W

[0048] Once the first processing step described above is completed, the wafer 10 is rotated 90 degrees together with the chuck table 35 to align the long sides 170, 170 along the second direction R2 with the X-axis direction. Then, the concentrator 41 of the laser beam irradiation means 4 is positioned at the processing start position of the long sides 170, 170, and the focal point of the laser beam LB2 based on the above laser processing conditions is positioned and irradiated onto the surface 10a' of the wafer 10', while the wafer 10 is fed in the X-axis direction to form a second processing mark consisting of divided grooves along the long sides 170, 170 of the wafer 10', thus completing the second processing step.

[0049] In this embodiment, as can be seen from Figure 7(b), which shows an enlarged view of area A in Figure 7(a), when the first and second machining processes are carried out to form the first and second machining marks along the short sides 160, 160 and the long sides 170, 170, an unmachined area S3 is formed at the intersection where the short sides 160 along the first direction R1 and the long sides 170 along the second direction R2 intersect, in which the first machining marks (dividing grooves on the short sides 160, 160) and the second machining marks (dividing grooves on the long sides 170, 170) are not formed. Note that in Figure 7(b), only area A shown in Figure 7(a) is enlarged, but the same unmachined area S3 is formed at all four intersections where the short sides 160, 160 along the first direction R1 and the long sides 170, 170 along the second direction R2 intersect.

[0050] Once the above-described unprocessed region S3 is formed, an unprocessed region processing step is performed to process the unprocessed region S3. In the unprocessed region processing step, as shown in Figure 7(b), a laser beam LB2 based on the above-described laser processing conditions is irradiated in a direction inclined with respect to the short side 160 along the first direction R1 and the long side 170 along the second direction R2, to form a connecting processing mark 180 consisting of a dividing groove that connects the end 160a of the short side 160 and the end 170a of the long side 170. The unprocessed region processing step is completed by performing the same processing on the unprocessed regions S3 of the other three intersections. With the above, the laser processing method of this embodiment is completed, and the wafer 10' can be divided into a plate-shaped member 11A and an annular member 11B.

[0051] According to the laser processing method of this embodiment, a first processing mark (dividing groove) formed along the short side 160 along the first direction R1 and a second processing mark (dividing groove) formed along the long side 170 along the second direction R2 perpendicular to the first direction R1 are connected by a connecting processing mark 180 formed at an angle. Since the short side 160 along the first direction R1 and the long side 170 along the second direction R2 do not intersect at the intersection, the problem of radial cracks of several tens of micrometers occurring at the intersection, which degrades the quality of the divided plate-like member 11A and the annular member 11B, is resolved.

[0052] In the embodiments described above, examples were shown in which a modified layer is formed by irradiating the wafer 10 with a laser beam LB1 of a wavelength that is transparent to the wafer 10 and positioning the focal point inside the wafer 10, and in which a divided groove is formed by irradiating the wafer 10 with a laser beam LB2 of a wavelength that is absorptive to the wafer 10 and positioning the focal point on the surface of the wafer 10 and performing ablation processing. However, the present invention is not limited thereto. For example, a shield tunnel that serves as the starting point for division is formed by positioning the focal point of a laser beam of a wavelength that is transparent to the wafer 10 at a required position on the wafer 10 and irradiating it, and forming a pore and a modified layer surrounding the pore. The laser processing conditions when forming the shield tunnel may be set to the following conditions, for example (for details of other processing conditions, see Patent Document 2 above). Wavelength: 1064nm Repetition frequency: 100kHz Spot diameter: 2 μm Irradiation interval: 5μm Average output: 4W

[0053] Furthermore, in the embodiments described above, examples were shown in which the plate-shaped workpieces, wafers 10 and 10', processed by the laser processing method of the present invention, are made of silicon (Si). However, the present invention is not limited to this, and for example, gallium arsenide (GaAs) wafers may also be used. Moreover, the plate-shaped workpiece may be a hexagonal wafer such as a silicon carbide (SiC) wafer, lithium tantalate (LT) wafer, or silicon dioxide (SiO2) wafer. Furthermore, in the embodiments described above, the case in which the crystal orientation D of the workpiece wafer 10 is tilted 45 degrees in a plan view with respect to the first planned division line 14a and the second planned division line 14b was described, but the present invention is not limited to this, and the above effects can be obtained by the laser processing method of the present invention regardless of the direction of the crystal orientation D. [Explanation of symbols]

[0054] 1: Laser processing equipment 2: Base 2a, 2a: Guide rail 3: Holding means 31:X-axis movable plate 31a, 31a: Guide rail 32: Y-axis movable plate 33: Post 34: Cover board 35: Chuck Table 36: Suction Chuck 37: Clamp 4: Laser beam irradiation means 41: Light concentrator 5: Imaging means 6: Processing feed means 61:X-axis movement means 62: Y-axis movement means 7:Frame body 7a: Vertical wall 7b:Horizontal wall 10: Wafer 12: Devices 14: Planned division line 14a: First planned division line 14b: Second planned division line 16: Notch 20: Control means 100: First processing mark 110: Second processing mark 120a, 120b: Connection machining marks 122a, 122b: Connection machining marks 130: First processing mark 140: Second processing mark 150a, 150b: Connection machining marks 152a, 152b: Connection machining marks 160: Short side 160a: End 170: Long side 170a: End 180: Connection machining marks

Claims

1. A laser processing method that processes a plate-shaped workpiece by irradiating it with a laser beam, A first processing step involves irradiating a laser beam in a first direction to form a starting point for division or a division groove, thereby forming a first processing mark, A second processing step involves irradiating a laser beam in a second direction intersecting the first direction to form a starting point for division or a division groove, thereby forming a second processing mark. Equipped with, In the first or second processing step, at the intersection where the first direction and the second direction intersect, an unprocessed area is formed where no processing is performed. The process further comprises a raw area processing step for processing the raw area, The unprocessed area processing step involves irradiating a laser beam in a direction inclined with respect to the first direction or the second direction to form a starting point for division or a division groove, thereby forming a connecting processing mark that connects the first processing mark and the second processing mark. The end of the second processing mark along the second direction on one side of the unprocessed area is used as the base end, and a laser beam is irradiated at an angle between the first direction and the first direction, so as not to be perpendicular to the first direction, thereby forming a connecting processing mark that connects the first processing mark and the second processing mark, which are made of a modified layer. Furthermore, the second processing mark along the second direction on the other side of the unprocessed area... A laser processing method comprising irradiating a laser beam with an inclination between the first direction and the first direction, using the end of the work mark as the base end, to form a connecting work mark that connects the first work mark and the second work mark, which are made of a modified layer, wherein the connecting work mark formed with the end of the second work mark on one side of the unprocessed area as the base end and the connecting work mark formed with the end of the second work mark on the other side of the unprocessed area as the base end are not connected at the same location in the first work mark, by appropriately adjusting the inclination angle of each connecting work mark or the position of the base end when forming each connecting work mark.

2. The laser processing method according to claim 1, wherein the first processing mark and the second processing mark are modified layers formed by irradiating the workpiece with a laser beam having a wavelength that is transparent to the workpiece, with the focal point positioned inside the workpiece.

3. The laser processing method according to claim 1, wherein the first processing mark and the second processing mark are shield tunnels formed from pores and altered layers surrounding the pores by irradiating the workpiece with a laser beam of a wavelength that is transparent to the workpiece, with the focal point positioned at a required position on the workpiece.

4. The laser processing method according to claim 1, wherein the first processing mark and the second processing mark are grooves formed by ablation processing by irradiating the workpiece with a laser beam having a wavelength that is absorbable to the workpiece, with the focal point positioned at a required position on the workpiece.

5. The laser processing method according to claim 1, wherein the plate-shaped workpiece is a wafer on which a plurality of devices are partitioned by division lines and formed on its surface, and the first direction and the second direction are the directions of the division lines.

6. The laser processing method according to any one of claims 1 to 5, wherein the plate-shaped workpiece is a Si wafer or GaAs wafer in which the crystal orientation and the first direction and the second direction are tilted by 45 degrees.

7. Plate-shaped workpieces include SiC wafers, LT wafers, and SiO2 wafers. ２ A laser processing method according to any one of claims 1 to 5, wherein the wafer is a hexagonal wafer.

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