Laser processing method

Abstract

The objective is to reduce the risk of defects occurring when multiple branched beams, separated from a laser beam using a diffractive optical element, are focused onto a workpiece, due to diffracted light of an order that does not contribute to processing being focused onto the workpiece. [Solution] The laser processing method is a laser processing method that irradiates a laser beam onto a street set on an object to be processed, and comprises a branching step 1001 in which a diffractive optical element is used to branch the laser beam into a plurality of branched beams including processing light to irradiate the street and unwanted light to irradiate the device, and a focusing irradiation step 1002 in which the plurality of branched beams are each focused and irradiated from the surface side of the object to be processed, wherein the irradiation diameter of the area irradiated by one unwanted light, a branched beam, on the surface is set to be larger than the irradiation diameter of the area irradiated by one processing light, a branched beam.

Description

Technical Field

[0001] The present invention relates to a laser processing method.

Background Art

[0002] There has been proposed a laser processing apparatus that branches and condenses a single laser beam into a plurality of laser beams using a diffractive optical element and a condenser lens, and irradiates the plurality of laser beams onto a processing line (processing region) to simultaneously perform a plurality of linear processes (for example, see Patent Document 1).

[0003] In an optical system that branches a laser beam using the diffractive optical element shown in Patent Document 1, in addition to the light of the order that is irradiated onto the processing region and contributes to processing, higher-order light and zero-order light that are not irradiated onto the processing region and do not contribute to processing are generated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the laser processing apparatus shown in Patent Document 1, since the light of the order that does not contribute to processing is also condensed onto the surface side of the workpiece by the condenser lens, there is a problem that the region (device region) other than the processing region on the workpiece is damaged.

[0006] If these lights are condensed and irradiated onto the device region formed on the workpiece, the device may be destroyed or defects may occur in the device in subsequent processes.

[0007] ​This invention has been made in view of the above problems, and aims to reduce the risk of defects occurring when multiple branched beams, branched from a laser beam using a diffractive optical element, are focused and irradiated onto a workpiece, due to diffractive beams of an order that do not contribute to processing being focused and irradiated onto the workpiece. [Means for solving the problem]

[0008] To solve the above-mentioned problems and achieve the objective, the present invention provides a laser processing method for irradiating a processing area set on an object to be processed with a laser beam, comprising: a branching step of using a diffractive optical element to branch the laser beam into a plurality of branched beams including processing light to irradiate the processing area and unwanted light to irradiate a non-processing area; and a focusing irradiation step of focusing each of the plurality of branched beams and irradiating from one side of the object to be processed, wherein the irradiation diameter on the one surface irradiated by one of the unwanted beams is set to be larger than the irradiation diameter on the one of the processing beams.

[0009] In the laser processing method described above, the energy density of one unwanted light beam irradiated onto the unprocessed region on the surface may be less than the energy density required to alter the unprocessed region.

[0010] In the laser processing method described above, the object to be processed may have a plurality of streets and device areas demarcated by the streets on one surface, the processing areas may be set on the streets, and the non-processing areas may be set on the device areas. [Effects of the Invention]

[0011] The present invention has the effect of reducing the risk of defects occurring when multiple branched beams, branched from a laser beam using a diffractive optical element, are focused and irradiated onto a workpiece, due to diffractive beams of an order that do not contribute to processing being focused and irradiated onto the workpiece. [Brief explanation of the drawing]

[0012] [Figure 1]Figure 1 is a schematic perspective view showing an object to be processed by the laser processing method according to Embodiment 1. [Figure 2] Figure 2 is a perspective view showing an example of the configuration of a laser processing apparatus for implementing the laser processing method according to Embodiment 1. [Figure 3] Figure 3 is a schematic diagram showing the configuration of the laser beam irradiation unit and other components of the laser processing apparatus shown in Figure 2. [Figure 4] Figure 4 is a flowchart showing the flow of the laser processing method according to Embodiment 1. [Figure 5] Figure 5 is a schematic diagram showing the laser processing of an object in the comparative example laser processing method. [Figure 6] Figure 6 is a schematic diagram showing a partial cross-section of the laser processing of an object to be processed in a laser processing method according to a modified embodiment of Embodiment 1. [Figure 7] Figure 7 is a schematic diagram showing, in partial cross-section, another state in which the workpiece is laser-processed in the laser processing method according to a modified embodiment of Embodiment 1. [Modes for carrying out the invention]

[0013] Embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by those skilled in the art, and those that are substantially the same. In addition, the components described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the present invention.

[0014] [Embodiment 1] A laser processing method according to Embodiment 1 of the present invention will be described with reference to the drawings. Figure 1 is a schematic perspective view showing an object to be processed by the laser processing method according to Embodiment 1. Figure 2 is a perspective view showing an example of the configuration of a laser processing apparatus for implementing the laser processing method according to Embodiment 1. Figure 3 is a schematic diagram showing the configuration of the laser beam irradiation unit and the like of the laser processing apparatus shown in Figure 2. Figure 4 is a flowchart showing the flow of the laser processing method according to Embodiment 1. Figure 5 is a schematic diagram showing the state of laser processing of an object in a comparative example laser processing method.

[0015] (Object to be processed) The laser processing method according to Embodiment 1 is a method of laser processing (equivalent to laser processing) of the workpiece 200 shown in Figure 1. The workpiece 200 shown in Figure 1, which is the target of the laser processing method according to Embodiment 1, is a wafer such as a disc-shaped semiconductor wafer or optical device wafer with a substrate made of silicon, GaAs, InP, GaN, or SiC.

[0016] As shown in Figure 1, the workpiece 200 comprises a plurality of intersecting streets 202 on a surface 201 (corresponding to one surface) and devices 203 (corresponding to device regions) formed in each region partitioned in a grid pattern by the streets 202. The devices 203 are, for example, integrated circuits such as ICs (Integrated Circuits) or LSIs (Large Scale Integrations), image sensors such as CCDs (Charge Coupled Devices) or CMOSs ​​(Complementary Metal Oxide Semiconductors), MEMS (Micro Electro Mechanical Systems), or semiconductor memory (semiconductor memory devices).

[0017] (Laser processing equipment) The laser processing method shown in Embodiment 1 is implemented by the laser processing apparatus 1 shown in FIG. 2. Next, the laser processing apparatus 1 will be described. The laser processing apparatus 1 is a processing apparatus that laser-processes the workpiece 200. As shown in FIG. 2, the laser processing apparatus 1 includes a holding unit 10, a moving unit 30, a laser beam irradiation unit 20, an imaging unit 40, and a control unit 100.

[0018] The holding unit 10 has a disk shape, and a flat holding surface 11 along the horizontal direction for holding the workpiece 200 is formed of porous ceramic or the like. Further, the holding unit 10 is movably provided over the processing area below the laser beam irradiation unit 20 by the moving unit 30 and the loading / unloading area where the workpiece 200 is loaded and unloaded while being separated from below the laser beam irradiation unit 20.

[0019] The holding unit 10 is connected to a vacuum suction source (not shown), and by being suctioned from the vacuum suction source, the workpiece 200 placed on the holding surface 11 is suctioned and held. In Embodiment 1, as shown in FIGS. 2 and 3, the holding unit 10 sucks and holds the back surface 204 side on the back side of the surface 201 of the workpiece 200.

[0020] The moving unit 30 relatively moves the holding unit 10 and the laser beam irradiation unit 20. The moving unit 30 includes a Y-axis moving unit 31 which is a indexing feed unit that moves the holding unit 10 in the Y-axis direction parallel to the horizontal direction, an X-axis moving unit 32 which is a processing feed unit that moves the holding unit 10 in the X-axis direction parallel to the horizontal direction and orthogonal to the Y-axis direction, and a rotational moving unit 33 that rotates around an axis parallel to the Z-axis direction which is orthogonal to both the X-axis direction and the Y-axis direction and parallel to the vertical direction.

[0021] The Y-axis movement unit 31 is installed on the main body 2 of the device and moves the holding unit 10 in the Y-axis direction by moving the moving plate 3 on which the X-axis movement unit 32 is installed in the Y-axis direction. The X-axis movement unit 32 is installed on the moving plate 3 and moves the holding unit 10 in the X-axis direction by moving the second moving plate 4 on which the rotational movement unit 33 is installed in the X-axis direction. The rotational movement unit 33 is installed on the second moving plate 4 and rotates the holding unit 10 around its axis by supporting the holding unit 10.

[0022] The Y-axis movement unit 31 moves the movement plate 3, the X-axis movement unit 32, the second movement plate 4, the rotation movement unit 33, and the holding unit 10 in the Y-axis direction. The X-axis movement unit 32 moves the second movement plate 4, the rotation movement unit 33, and the holding unit 10 in the X-axis direction.

[0023] The Y-axis moving unit 31 and the X-axis moving unit 32 are equipped with a well-known ball screw rotatably mounted around its axis, a well-known motor for rotating the ball screw around its axis, and a well-known guide rail for supporting the moving plates 3 and 4 so that they can move in the Y-axis direction or the X-axis direction. The rotary moving unit 33 is equipped with a well-known motor for rotating the holding unit 10 around its axis.

[0024] As shown in Figure 1, the laser beam irradiation unit 20 is partially provided at the tip of a support column 6, the base of which is fixed to an upright wall 5 erected from the Y-axis end of the main body of the apparatus 2. The laser beam irradiation unit 20 is a processing unit that laser processes the workpiece 200 held by the holding unit 10.

[0025] In Embodiment 1, as shown in Figure 3, the laser beam irradiation unit 20 includes a laser oscillator 22 that emits a laser beam 21 with a wavelength that is absorbed by the workpiece 200, a diffractive optical element 23 that splits the laser beam 21 emitted by the laser oscillator 22 into a plurality of branched beams 211, a mirror 24 that reflects the laser beam 21 emitted by the laser oscillator 22 toward the diffractive optical element 23, and a focusing lens 25 that focuses the branched beams 211 split by the diffractive optical element 23.

[0026] The diffractive optical element 23 splits the laser beam 21 into a 0th-order branched beam 211 (hereinafter referred to as 211-0), a -1st-order branched beam 211 (hereinafter referred to as 211-1), a +1st-order branched beam 211 (hereinafter referred to as 211+1), a -2nd-order branched beam 211 (hereinafter referred to as 211-2), a +2nd-order branched beam 211 (hereinafter referred to as 211+2), and a higher-order branched beam (not shown). In Embodiment 1, the diffractive optical element 23 splits the laser beam 21 in the Y-axis direction such that branched beams 211-2, 211-1, 211-0, 211+1, and 211+2 are located side by side in the Y-axis direction.

[0027] Furthermore, in Embodiment 1, the diffractive optical element 23 is configured to irradiate a portion of the multiple branched lights 211-2, 211-1, 211-0, 211+1, 211+2 onto the street 202, which is the processing area, as processing light 220 for ablation processing of the street 202, and to irradiate the remainder onto the device 203, which is the non-processing area, as unwanted light 221. The surface shape of the diffractive optical element 23 is configured to be of various shapes such that the focal point 222 of the unwanted light 221, which is focused by the focusing lens 25, is located closer to the focusing lens 25 than the focal point 222 of the unwanted light 221, which is focused by the focusing lens 25.

[0028] The diffractive optical element 23 has a surface shape that can be set to various shapes, so that a portion of the multiple branched lights 211-2, 211-1, 211-0, 211+1, and 211+2 are set as processing light 220, and the remainder as unwanted light 221. In Embodiment 1, the diffractive optical element 23 has the 0th-order branched light 211-0, the -1st-order branched light 211-1, and the +1st-order branched light 211+1 set as processing light 220, and the -2nd-order branched light 211-2 and the +2nd-order branched light 211+2 set as unwanted light 221.

[0029] Thus, in Embodiment 1, the processing area is set on the street 202, and the non-processing area is set on the device 203. Furthermore, the diffractive optical element 23 cannot change any of the multiple branched lights 211-2, 211-1, 211-0, 211+1, and 211+2 that have been set as processing light 220, nor can it change any that have been set as unwanted light 221. For example, once the 0th-order branched light 211-0 is set as processing light 220, the diffractive optical element 23 cannot change the 0th-order branched light 211-0 to unwanted light 221, and once the -2nd-order branched light 211-2 is set as unwanted light 221, the diffractive optical element 23 cannot change the -2nd-order branched light 211-2 to processing light 220.

[0030] In Embodiment 1, the laser beam irradiation unit 20 uses a diffractive optical element 23 to split a laser beam 21 that is absorbent to the workpiece 200 into a plurality of branched beams 211-2, 211-1, 211-0, 211+1, 211+2, which include processing light 220 and unwanted light 221. The focal point 222 of the branched beams 211-1, 211-0, 211+1, which are set to the processing light 220, is set on the surface 201 of the street 202 of the workpiece 200, and the beam is irradiated along the street 202 to perform ablation processing on the surface 201 of the street 202 of the workpiece 200. In Embodiment 1, the laser beam irradiation unit 20 irradiates the surface 201 of the same street 202 with branched beams 211-1, 211-0, and 211+1 set as processing beam 220, and irradiates the adjacent device 203 of the street 202 to be ablated with branched beams 211-2 and 211+2 set as unwanted beam 221, thereby ablating one street 202 simultaneously.

[0031] For this reason, on the surface 201 of the workpiece 200, the irradiation diameter 221-1 of the region irradiated by the branched light 211-2,211+2 set as one unwanted light 221 is set to be larger than the irradiation diameter 220-1 of the region irradiated by the branched light 211-1,211-0,211+1 set as one processing light 220. Furthermore, on the device 203 on the surface 201 of the workpiece 200, the output of the laser beam 21 oscillated by the laser oscillator 22, the distance in the Z-axis direction between the focal point 222 of the branched light 211-2,211+2 set as one unwanted light 221 and the focal point 222 of the branched light 211-2,211+2 set as one processing light 220 are set so that the energy density on the surface 201 of the device 203 irradiated by the branched light 211-2,211+2 set as one unwanted light 221 is lower than the energy density required to alter the device 203.

[0032] Thus, in Embodiment 1, the laser beam irradiation unit 20 performs ablation on the street 202 of the workpiece 200, but does not perform ablation on the device 203 of the workpiece 200. In Embodiment 1, the positions of the focal points 222 in the Z-axis direction of the 0th-order branched light 211-0, -1st-order branched light 211-1, and +1st-order branched light 211+1 set in the processing light 220 are equal. In Embodiment 1, the positions of the focal points 222 in the Z-axis direction of the -2nd-order branched light 211-2 and +2nd-order branched light 211+2 set in the unwanted light 221 are equal.

[0033] In this invention, the laser beam 21 emitted by the laser oscillator 22 of the laser beam irradiation unit 20 has a wavelength that is absorbent to the workpiece 200, but in this invention, it may also have a wavelength that is transparent to the workpiece 200. When the laser beam 21 has a wavelength that is transparent to the workpiece 200, the laser processing apparatus 1 forms a modified layer inside the workpiece 200 along the street 202.

[0034] The modified layer refers to a region whose density, refractive index, mechanical strength, and other physical properties differ from those of the surrounding area. Examples include melted regions, cracked regions, dielectric breakdown regions, refractive index change regions, and regions where these regions are mixed. Furthermore, the modified layer has lower mechanical strength and other properties than other parts of the treated object 200.

[0035] The imaging unit 40 is installed at the tip of the support column 6 and is positioned in line with the focusing lens 25 of the laser beam irradiation unit 20 in the X-axis direction. The imaging unit 40 is equipped with an image sensor that captures the area to be processed of the workpiece 200 held by the holding unit 10 before cutting. The image sensor is, for example, a CCD (Charge-Coupled Device) image sensor or a CMOS (Complementary MOS) image sensor. The imaging unit 40 captures the workpiece 200 held by the holding unit 10 to obtain an image for performing alignment between the workpiece 200 and the laser beam irradiation unit 20, and outputs the obtained image to the control unit 100.

[0036] The control unit 100 controls each component of the laser processing apparatus 1 to cause the laser processing apparatus 1 to perform processing operations on the workpiece 200. The control unit 100 is a computer having a computing laser processing device with a microprocessor such as a CPU (central processing unit), a storage device with memory such as ROM (read-only memory) or RAM (random access memory), and an input / output interface device. The computing laser processing device of the control unit 100 performs calculation processing according to the computer program stored in the storage device and outputs control signals for controlling the laser processing apparatus 1 to each component of the laser processing apparatus 1 via the input / output interface device.

[0037] The control unit 100 is connected to a display unit (not shown) which consists of a liquid crystal display device that displays the status of processing operations and images, an input unit (not shown) used by the operator to register processing conditions, and a notification unit that notifies the operator. The input unit consists of at least one of a touch panel provided on the display unit and an external input device such as a keyboard. The notification unit notifies the operator by emitting at least one of sound, light, and / or a display, and may also be used by the display unit.

[0038] (Laser processing method) Next, a laser processing method according to Embodiment 1 will be described. The laser processing method according to Embodiment 1 is a method of laser processing a workpiece 200 using the laser processing apparatus 1 with the configuration described above. That is, the laser processing method according to Embodiment 1 is a method in which the laser processing apparatus 1 with the configuration described above irradiates a laser beam 21 onto a street 202, which is a processing area set on the workpiece 200.

[0039] The processing method according to Embodiment 1 comprises a branching step 1001 and a focusing irradiation step 1002, as shown in Figure 4.

[0040] In Embodiment 1, the laser processing apparatus 1 registers processing conditions in the control unit 100 by an operator or the like, and the back surface 204 side of the workpiece 200 is placed on the holding surface 11 of the holding unit 10. In Embodiment 1, when the control unit 100 receives a processing start instruction from an operator or the like, the control unit 100 starts the processing operation and holds the back surface 204 side of the workpiece 200 on the holding surface 11 of the holding unit 10 by suction.

[0041] In Embodiment 1, the laser processing apparatus 1 has a control unit 100 that controls a moving unit 30 to move the holding unit 10 from the loading / unloading area towards the processing area to below the imaging unit 40, and the imaging unit 40 images the workpiece 200 held by the holding unit 10 to perform alignment.

[0042] In Embodiment 1, the laser processing apparatus 1 controls the moving unit 30 and the laser beam irradiation unit 20, etc., based on processing conditions, and the moving unit 30 moves the focusing lens 25 of the laser beam irradiation unit 20 and the workpiece 200 relatively along the street 202 while irradiating the workpiece 200 with branched beams 211-2, 211-1, 211-0, 211+1, 211+2 from the laser beam irradiation unit 20.

[0043] In Embodiment 1, the laser processing apparatus 1 moves the focusing lens 25 of the laser beam irradiation unit 20 and the workpiece 200 along the street 202 relative to each other, and irradiates the workpiece with branched light 211-2, 211-1, 211-0, 211+1, 211+2 from the laser beam irradiation unit 20, performing the branching step 1001 and the focusing irradiation step 1002 in succession.

[0044] (Branching step) The branching step 1001 is a step in which the laser beam 21 is branched into a plurality of branched beams 211-2, 211-1, 211-0, 211+1, 211+2, which include processing light 220 that irradiates the street 202, which is the processing area, and unwanted light 221 that irradiates the device 203, which is the non-processing area, using the diffractive optical element 23. In Embodiment 1, in the branching step 1001, the laser processing apparatus 1 has a control unit 100 that controls the laser beam irradiation unit 20 to oscillate the laser beam 21 from the laser oscillator 22. Then, in the branching step 1001, the diffractive optical element 23 branches the laser beam 21 into a plurality of branched beams 211-2, 211-1, 211-0, 211+1, 211+2.

[0045] (Concentrated light irradiation step) The focusing irradiation step 1002 is a step in which multiple branched lights 211-2, 211-1, 211-0, 211+1, and 211+2 are focused and irradiated from the surface 201 side of the workpiece 200. In Embodiment 1, in the focusing irradiation step 1002, the focusing lens 25 focuses the branched lights 211-2, 211-1, 211-0, 211+1, and 211+2 and irradiates the surface 201 side of the workpiece 200.

[0046] In Embodiment 1, during the focusing and irradiation step 1002, the diffractive optical element 23 splits the laser beam 21 into branched light 211-1, 211-0, 211+1, which are the processing light 220, and branched light 211-2, 211+2, which are the unwanted light 221. Therefore, the focusing lens 25 of the laser beam irradiation unit 20 sets the focusing point 222 of the branched light 211-1, 211-0, 211+1, which are the processing light 220, to the surface 201 of the street 202, and sets the focusing point 222 of the branched light 211-2, 211+2, which are the unwanted light 221, to the side of the focusing lens 25 that is closer to the surface of the device 203. In Embodiment 1, during the focusing irradiation step 1002, the irradiation diameter 221-1 of the region where unwanted light 221, which is branched light 211-2, 211+2, is irradiated on the surface 201 of the workpiece 200 by the focusing lens 25 of the laser beam irradiation unit 20 is set to be larger than the irradiation diameter 220-1 of the region where the processing light 220, which is branched light 211-1, 211-0, 211+1, is irradiated. This ensures that the energy density of the unwanted light 221, which is branched light 211-2, 211+2, irradiated on the device 203 on the surface 201 is set to a value lower than the energy density required to alter the device 203.

[0047] During the processing operation, the laser processing apparatus 1 irradiates all streets 202 of the workpiece 200 with the laser beam 21, then stops the oscillation of the laser beam 21 from the laser oscillator 22, that is, ends the branching step 1001 and the focusing irradiation step, and moves the holding unit 10 from the processing area toward the loading / unloading area. During the processing operation, the laser processing apparatus 1 stops the movement of the holding unit 10 in the loading / unloading area, stops the suction holding of the workpiece 200 by the holding unit 10, and ends the processing operation.

[0048] In the comparative example laser processing method, which processes the workpiece 200 by splitting the laser beam 21 into branched beams 211-2, 211-1, 211-0, 211+1, and 211+2 so that the focal point 222 shown in Figure 5 is located at the same position in the Z-axis direction, the focal point 222 of the branched beams 211-2 and 211+2 is also located on the device 203, causing damage to the device 203. In contrast to this comparative example, the laser processing method according to Embodiment 1 described above has the irradiation diameter 221-1 of the area irradiated by the branched beams 211-2 and 211+2, which are unwanted beams 221 irradiated onto the device 203, which is a non-processing area other than the street 202 set on the surface 201 of the workpiece 200, set to be larger than the irradiation diameter 220-1 of the area irradiated by the branched beams 211-1, 211-0, and 211+1, which are processing beams 220 irradiated onto the street 202.

[0049] For this reason, the laser processing method according to Embodiment 1 can suppress damage to the device 203 caused by branched light 211-2, 211+2 of an order that does not contribute to the processing of the workpiece 200. As a result, the laser processing method according to Embodiment 1 has the effect of reducing the risk of defects occurring when a plurality of branched light 211-2, 211-1, 211-0, 211+1, 211+2 branched from the laser beam 21 using the diffractive optical element 23 is focused and irradiated onto the workpiece 200, due to branched light 211-2, 211+2 of an order that does not contribute to laser processing being focused and irradiated onto the device 203 of the workpiece 200. Note that in Figure 5, the same reference numerals are used for the same parts as in Embodiment 1 and their description is omitted.

[0050] In this invention, among the multiple branched lights 211-2, 211-1, 211-0, 211+1, and 211+2, any that irradiates the street 202 but irradiates an unintended area may be treated as unwanted light 221. For example, in Embodiment 1, among the branched lights 211-1, 211-0, and 211+1 irradiated onto the street 202, the 0th-order branched light 211-0 may be treated as unwanted light 221, and the irradiation diameter 221-1 of the 0th-order branched light 211-0 on the surface 201 may be made larger than the processing light 220.

[0051] [Variation] A modified version of the laser processing method according to Embodiment 1 will be described based on the drawings. Figure 6 is a schematic diagram showing a partial cross-section of the laser processing state of the workpiece according to the modified version of the laser processing method according to Embodiment 1. Figure 7 is a schematic diagram showing another partial cross-section of the laser processing state of the workpiece according to the modified version of the laser processing method according to Embodiment 1. Note that the same reference numerals are used for the same parts as in Embodiment 1 in Figures 6 and 7, and their descriptions are omitted.

[0052] Figures 6 and 7 show, in addition to branched beams 211-2, 211-1, 211-0, 211+1, and 211+2, a -3rd-order branched beam 211 (hereinafter referred to as reference numeral 211-3) and a 3rd-order branched beam 211 (hereinafter referred to as reference numeral 211+3). In the modified laser processing method, while the laser processing method according to Embodiment 1 ablates one street 202 simultaneously, the modified method ablates two adjacent streets 202 simultaneously.

[0053] In the modified examples shown in Figures 6 and 7, the laser processing apparatus 1 has the 0th-order branched light 211-0, the -2nd-order branched light 211-2, the +2nd-order branched light 211+2, the -3rd-order branched light 211-3, and the +3rd-order branched light 211+3 set as unwanted light 221, and the -1st-order branched light 211-1 and the +1st-order branched light 211+1 set as processing light 220. In the modified examples shown in Figures 6 and 7, the laser processing apparatus 1 simultaneously irradiates two adjacent streets 202 with branched light 211-1 and 211+1, thereby ablating two adjacent streets 202 at the same time.

[0054] In the modified examples shown in Figures 6 and 7, the laser processing apparatus 1 irradiates the device 203 with 0th-order branched light 211-0, -2nd-order branched light 211-2, and +2nd-order branched light 211+2. In the modified examples shown in Figures 6 and 7, the laser processing apparatus 1 irradiates the street 202 adjacent to the two streets 202 that simultaneously perform ablation processing with -3rd-order branched light 211-3 and +3rd-order branched light 211+3 (the street 202 irradiated with +3rd-order branched light 211+3 is indicated by the reference numeral 202-1).

[0055] Thus, in this modified example, even among the branched light 211-3, 211+3 irradiated onto street 202, those that are not subjected to ablation are set as unwanted light 221, making the irradiation diameter 221-1 on surface 201 larger than the irradiation diameter 220-1 of processing light 220.

[0056] In the modified laser processing method, the irradiation diameter 221-1 of the region irradiated with unwanted light 221, which is branched light 211-3, 211-2, 211-0, 211+2, 211+3, on the surface 201 of the workpiece 200 is set to be larger than the irradiation diameter 220-1 of the region irradiated with processing light 220, which is branched light 211-1, 211+1. For this reason, the modified laser processing method, similar to Embodiment 1, reduces the risk of defects occurring when multiple branched lights 211-3, 211-2, 211-1, 211-0, 211+1, 211+2, 211+3 branched from the laser beam 21 using the diffractive optical element 23 are focused and irradiated onto the workpiece 200, due to branched light 211-2, 211-0, 211+2 of an order that does not contribute to laser processing being focused and irradiated onto the device 203 of the workpiece 200.

[0057] Furthermore, in the modified laser processing method, as shown in Figure 6, the processing light 220, which is branched light 211-1, 211+1, is irradiated onto two adjacent streets 202, and then, as shown in Figure 7, the processing light 220, which is branched light 211-1, 211+1, is irradiated onto the next two adjacent streets 202. In this case, in the modified laser processing method, as shown in Figure 6, unwanted light 221, which is branched light 211+3, is irradiated onto street 202-1, and ablation processing of street 202-1 by branched light 211+3 can be suppressed, thus suppressing the occurrence of processing defects.

[0058] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention. [Explanation of symbols]

[0059] 21 Laser beams 23 Diffractive Optical Elements 200 Items to be processed 201 Surface (one side) 202 Streets (Processing Area) 203 Device (device area, unprocessed area) 211, 211-3, 211-2, 211-0, 211+2, 211+3 Branched light 220 Processing light 220-1 Irradiation diameter 221 Unnecessary light 221-1 Irradiation diameter 1001 Branching Step 1002 Focusing Irradiation Step

Claims

1. A laser processing method in which a laser beam is irradiated onto a processing area set on an object to be processed, A branching step in which the laser beam is branched into a plurality of branched beams including processing light to irradiate the processing area and unwanted light to irradiate the non-processing area using a diffractive optical element, The system includes a focusing irradiation step in which each of the multiple branched lights is focused and irradiated from one side of the object to be processed, A laser processing method in which, on the surface, the irradiation diameter to which one unwanted light is irradiated is set to be larger than the irradiation diameter to which one processing light is irradiated.

2. The laser processing method according to claim 1, wherein the energy density of one unwanted light beam irradiated in the unprocessed area on the surface is less than the energy density required to alter the unprocessed area.

3. The object to be processed comprises a plurality of streets on one surface and device areas demarcated by these streets, The laser processing method according to claim 1 or claim 2, wherein the processing area is set on the street and the non-processing area is set on the device area.

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