Laser processing apparatus and laser processing method

Abstract

To provide a laser processing apparatus that does not damage a device during laser processing and can obtain required processing results for various workpieces.SOLUTION: A laser processing apparatus includes a chuck table that holds a workpiece, laser beam irradiation means that irradiates the workpiece held on the chuck table with a pulsed laser beam LB, and feed means that relatively feeds the chuck table and the laser beam irradiation means for processing. The laser beam irradiation means includes an oscillator 36 that oscillates a pulsed laser beam, and a condenser 38 that condenses the pulsed laser beam LB oscillated by the oscillator 36 and irradiates the workpiece held on the chuck table with the beam. A repetition frequency of the pulsed laser beam LB oscillated by the oscillator 36 is set to be equal to or greater than a value obtained by multiplying a thermal conductivity λ[W / (m K)] of the workpiece by a coefficient β[MHz m K / W].SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a laser processing apparatus including a chuck table for holding a workpiece, a laser beam application means for applying a pulsed laser beam to the workpiece held on the chuck table, and a feeding means for relatively feeding the chuck table and the laser beam application means for processing, and a method for laser processing a workpiece. [Background technology]

[0002] Wafers, on the surface of which multiple devices such as ICs and LSIs are formed along planned dividing lines, are divided into individual device chips using a laser processing machine, and each of the divided device chips is used in electrical equipment such as mobile phones and personal computers.

[0003] The laser processing device includes a chuck table that holds the workpiece, a laser beam application means that irradiates the workpiece held on the chuck table with a pulsed laser beam, and a feed means that feeds the chuck table and the laser beam application means relative to each other for processing, and can perform desired processing on the wafer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6151557 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a wafer is made of SiC, if a pulsed laser beam is irradiated along the intended dividing line to form the starting point for dividing, cracks can propagate from the intended dividing line, following the crystal structure, and damage the device.

[0006] Furthermore, there is a problem that satisfactory processing results cannot be obtained even if various adjustments such as adjusting the output of the laser beam, adjusting the feed rate, or adjusting the position of the focal point are tried.

[0007] An object of the present invention is to provide a laser processing apparatus and a laser processing method that can obtain desired processing results for various workpieces without damaging devices during laser processing. [Means for solving the problem]

[0008] According to the present invention, there is provided the following laser processing apparatus that solves the above-mentioned problems. "A laser processing device including a chuck table for holding a workpiece, a laser beam application means for applying a pulsed laser beam to the workpiece held on the chuck table, and a feed means for relatively feeding the chuck table and the laser beam application means for processing, the laser beam application means includes an oscillator that oscillates a pulsed laser beam, and a condenser that condenses the pulsed laser beam oscillated by the oscillator and irradiates the workpiece held on the chuck table with the condensed laser beam; The repetition frequency of the pulsed laser beam emitted by the oscillator is set to a value equal to or greater than the thermal conductivity λ [W / (m·K)] of the workpiece multiplied by a coefficient β [MHz·m·K / W].

[0009] The coefficient β is preferably 0.2. The oscillator preferably includes a packet setting unit that sets a packet, each group consisting of an arbitrary number of pulsed laser beams, a quasi-repetition frequency setting unit that sets a quasi-repetition frequency for thinning out the pulsed laser beams between the packet and an adjacent packet, and a power amplifier that amplifies the power of the pulsed laser beam, and the packets are used to adjust the heating duration of the workpiece.

[0010] Furthermore, according to the present invention, there is provided the following laser processing method that solves the above problems: "A laser processing method for a workpiece, a preparation step of preparing a laser processing device including a chuck table for holding a workpiece, a laser beam application means for applying a pulsed laser beam to the workpiece held on the chuck table, and a feed means for relatively feeding the chuck table and the laser beam application means for processing; a holding step of holding a workpiece on the chuck table; a laser beam application step of applying a pulsed laser beam to the workpiece held on the chuck table to process the workpiece, The present invention provides a laser processing method in which the repetition frequency of an oscillator that oscillates a pulsed laser beam in the laser beam irradiation step is set to a value equal to or greater than the value obtained by multiplying the thermal conductivity λ [W / (m·K)] of the workpiece by a coefficient β [MHz·m·K / W]. [Effects of the Invention]

[0011] The laser processing apparatus of the present invention is A laser processing apparatus including a chuck table for holding a workpiece, a laser beam application means for applying a pulsed laser beam to the workpiece held on the chuck table, and a feed means for relatively feeding the chuck table and the laser beam application means for processing, the laser beam application means includes an oscillator that oscillates a pulsed laser beam, and a condenser that condenses the pulsed laser beam oscillated by the oscillator and irradiates the workpiece held on the chuck table with the condensed laser beam; The repetition rate of the pulsed laser beam emitted by the oscillator is set to a value equal to or greater than the thermal conductivity λ [W / (m·K)] of the workpiece multiplied by the coefficient β [MHz·m·K / W]. This prevents damage to the device during laser processing and enables desired processing results to be obtained for a variety of workpieces.

[0012] Further, the laser processing method of the present invention includes: a preparation step of preparing a laser processing device including a chuck table for holding a workpiece, a laser beam application means for applying a pulsed laser beam to the workpiece held on the chuck table, and a feed means for relatively feeding the chuck table and the laser beam application means for processing; a holding step of holding a workpiece on the chuck table; a laser beam application step of applying a pulsed laser beam to the workpiece held on the chuck table to process the workpiece, In the laser beam irradiation process, the repetition rate of the oscillator that generates the pulsed laser beam is set to a value equal to or greater than the thermal conductivity λ [W / (m·K)] of the workpiece multiplied by the coefficient β [MHz·m·K / W]. This prevents damage to the device during laser processing and enables desired processing results to be obtained for a variety of workpieces. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view of a laser processing apparatus according to the present invention; [Figure 2] 2 is a schematic diagram of the laser beam application means shown in FIG. 1. [Figure 3] FIG. 3 is a block diagram showing a first configuration of the oscillator shown in FIG. 2; [Figure 4] (a) A block diagram showing a second configuration of the oscillator shown in FIG. 2, (b) A schematic diagram of a pulsed laser beam emitted from the oscillator shown in (a). DETAILED DESCRIPTION OF THE INVENTION

[0014] First, a preferred embodiment of a laser processing apparatus according to the present invention will be described with reference to the drawings.

[0015] (Laser processing equipment 2) Referring to FIG. 1, the laser processing device 2 includes a chuck table 4 for holding a workpiece, a laser beam application means 6 for irradiating the workpiece held on the chuck table 4 with a pulsed laser beam, and a feed means 8 for relatively feeding the chuck table 4 and the laser beam application means 6 for processing.

[0016] (Chuck table 4 of laser processing device 2) A circular suction chuck 10 is disposed on the upper end of the chuck table 4. The suction chuck 10 is formed from a porous material such as porous ceramics. The suction chuck 10 is connected to a suction means (not shown). The suction means generates a suction force on the upper surface of the chuck table 4, so that a workpiece placed on the upper surface of the suction chuck 10 is sucked and held. A plurality of clamps 12 are disposed around the periphery of the chuck table 4 at intervals in the circumferential direction.

[0017] The chuck table 4 is configured to be movable in the X-axis direction indicated by the arrow X in FIG. 1 and the Y-axis direction indicated by the arrow Y in FIG. 1 (a direction perpendicular to the X-axis direction). The laser processing apparatus 2 of this embodiment includes an X-axis movable plate 16 mounted on the upper surface of a base 14 so as to be movable in the X-axis direction, a Y-axis movable plate 18 mounted on the upper surface of the X-axis movable plate 16 so as to be movable in the Y-axis direction, a support column 20 fixed to the upper surface of the Y-axis movable plate 18, and a cover plate 22 fixed to the upper end of the support column 20. The cover plate 22 has an elongated hole 22a extending in the Y-axis direction. The chuck table 4 is mounted on the upper end of the support column 20 through the elongated hole 22a in the cover plate 22. Therefore, the chuck table 4 is configured to be movable in the X-axis direction and the Y-axis direction via the X-axis movable plate 16 and the Y-axis movable plate 18. The chuck table 4 is rotated around an axis extending in the vertical direction by a motor (not shown) built into the support column 20. The XY plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

[0018] (Feeding means 8 of laser processing device 2) Before describing the laser beam application means 6, we will first describe the feeding means 8. The feeding means 8 of this embodiment includes an X-axis feeding means 24 that feeds the chuck table 4 in the X-axis direction for processing, and a Y-axis feeding means 26 that indexes and feeds the chuck table 4 in the Y-axis direction.

[0019] The X-axis feed means 24 has a ball screw 28 that is connected to the X-axis movable plate 16 and extends in the X-axis direction, and a motor 30 that rotates the ball screw 28. The X-axis feed means 24 converts the rotational motion of the motor 30 into linear motion using the ball screw 28 and transmits it to the X-axis movable plate 16, moving the X-axis movable plate 16 in the X-axis direction along the guide rails 14a on the base 14. As a result, the chuck table 4 is fed for processing in the X-axis direction.

[0020] The Y-axis feed means 26 has a ball screw 32 connected to the Y-axis movable plate 18 and extending in the Y-axis direction, and a motor 34 that rotates the ball screw 32. The Y-axis feed means 26 converts the rotational motion of the motor 34 into linear motion using the ball screw 32 and transmits it to the Y-axis movable plate 18, moving the Y-axis movable plate 18 in the Y-axis direction along the guide rails 16a on the X-axis movable plate 16. This causes the chuck table 4 to be indexed and fed in the Y-axis direction.

[0021] (Laser beam irradiation means 6 of laser processing device 2) As shown in FIG. 2, the laser beam application means 6 includes an oscillator 36 that oscillates a pulsed laser beam LB, and a condenser 38 that collects the pulsed laser beam LB generated by the oscillator 36 and irradiates the workpiece held on the chuck table 4 with the collected laser beam. A mirror 40 is provided between the oscillator 36 and the condenser 38 to guide the pulsed laser beam LB generated by the oscillator 36 to the condenser 38. As shown in FIG. 1, the laser beam application means 6 also has a housing 42 that extends upward from the upper surface of the base 14 and then extends substantially horizontally. The oscillator 36 is accommodated inside the housing 42, and the condenser 38 is attached to the lower surface of the tip of the housing 42. Furthermore, an imaging means 44 is attached to the lower surface of the tip of the housing 42 for imaging the workpiece held on the chuck table 4.

[0022] The repetition frequency F of the pulsed laser beam LB oscillated by the oscillator 36 is set to a value equal to or greater than the thermal conductivity λ [W / (m·K)] of the workpiece multiplied by a coefficient β [MHz·m·K / W] (see Equation 1 below). Equation 1 F≧λ·β The coefficient β is preferably 0.2 [MHz m K / W]. For example, if the workpiece is quartz, the thermal conductivity of quartz is 1.4 [W / (m K)], so the value λ·β obtained by multiplying the thermal conductivity λ by the coefficient β is: λ β = 1.4 × 0.2 = 0.28 Therefore, when the workpiece is made of quartz, the repetition frequency F of the pulsed laser beam LB oscillated by the oscillator 36 is set to 0.28 MHz or higher.

[0023] (The oscillator 36a of the laser beam application means 6: configuration shown in FIG. 3) An oscillator 36 that oscillates a pulsed laser beam LB having the repetition frequency F as described above has, for example, the configuration shown in Fig. 3. The oscillator 36a shown in Fig. 3 includes a plurality of seeders 46-1, 46-2, 46-3, ..., 46-n (hereinafter, these may be collectively referred to as "seeders 46") and a power amplifier 48 that amplifies the power of the pulsed laser beam LB oscillated from any of the plurality of seeders 46.

[0024] (Seeder 46 of oscillator 36a) The plurality of seeders 46 oscillate pulsed laser beams LB at different repetition frequencies. The repetition frequencies of the plurality of seeders 46 can be set in stages, for example, between 10 MHz and 1 GHz. Specific examples of the repetition frequencies of the plurality of seeders 46 are as follows: Seeder 46-1: Repetition rate 10MHz Seeder 46-2: Repetition rate 30MHz Seeder 46-3: Repetition rate 50MHz … Seeder 46-n: Repetition rate 1GHz However, the repetition frequency of the plurality of seeders 46 is not limited to the above value, and the number of the plurality of seeders 46 may be any number.

[0025] 3, a seeder having a repetition frequency F equal to or greater than the thermal conductivity λ [W / (m·K)] of the workpiece multiplied by a coefficient β [MHz·m·K / W] is selected from the plurality of seeders 46. The pulsed laser beam LB oscillated by the selected seeder is adjusted to an appropriate power by a power amplifier 48, reflected by a mirror 40, and directed to a condenser 38, where it is irradiated onto the workpiece.

[0026] (The oscillator 36b of the laser beam application means 6: configuration shown in FIG. 4) The oscillator 36 that oscillates the pulsed laser beam LB having the repetition rate F may have the configuration shown in Fig. 4(a). The oscillator 36b shown in Fig. 4(a) includes a seeder 50, a packet setting unit 52, a quasi-repetition rate setting unit 54, and a power amplifier 56.

[0027] (Seeder 50 of oscillator 36b) The seeder 50 is configured to oscillate a pulsed laser beam LB at a relatively high repetition rate. The repetition rate of the pulsed laser beam LB oscillated by the seeder 50 may be, for example, 10 GHz.

[0028] (Packet setting unit 52 of oscillator 36b) The packet setting unit 52 sets a packet P, with an arbitrary number of pulsed laser beams LB as one group. For example, as shown in FIG. 4(b), the packet setting unit 52 sets a packet P, with 10 pulses (10 pulses) of pulsed laser beams LB oscillated by the seeder 50 as one group (1 packet: 10 pulses). In addition, the packet setting unit 52 can adjust the number of pulses included in one packet P, thereby adjusting the quasi-pulse width τ (the pulse width when one packet P is considered as one pulse), which is the time width of one packet P.

[0029] (Quasi-repetition frequency setting unit 54 of oscillator 36b) The quasi-repetition frequency setting unit 54 sets a quasi-repetition frequency Fs for thinning out the pulsed laser beam LB between a packet P and an adjacent packet P. The quasi-repetition frequency Fs is the repetition frequency of the packet P, and is the reciprocal of the quasi-pulse interval t, which is the time interval between packets P (Fs=1 / t).

[0030] (Power amplifier 56 of oscillator 36b) The power amplifier 56 amplifies the power of the pulsed laser beam LB. Specifically, the power amplifier 56 amplifies the power of the pulsed laser beam LB for which the number of pulses included in one packet P has been set by the packet setting unit 52 and the quasi-repetition frequency Fs (the repetition frequency of the packet P) has been set by the quasi-repetition frequency setting unit 54.

[0031] 4(a), the quasi-repetition frequency Fs (the repetition frequency of the packet P) is set to a value equal to or greater than the thermal conductivity λ [W / (m·K)] of the workpiece multiplied by the coefficient β [MHz·m·K / W]. The pulsed laser beam LB, whose quasi-repetition frequency Fs has been set to an appropriate value, is adjusted to an appropriate power by the power amplifier 56, and is then reflected by the mirror 40 and guided to the condenser 38, where it is irradiated onto the workpiece.

[0032] In addition, in the oscillator 36b shown in Figure 4(a), the duration of heating in the workpiece (the duration of heating in the workpiece caused by irradiation with the pulsed laser beam LB) can be adjusted by adjusting the quasi-pulse width τ of the packet P.

[0033] (Workpiece) FIG. 2 also shows a disk-shaped wafer 58 as a workpiece that can be processed by the laser processing apparatus 2. The wafer 58 can be made of materials such as quartz, sapphire, SiC, or diamond. A front surface 58a of the wafer 58 is partitioned into a plurality of rectangular regions by grid-like dividing lines 60. A device 62 such as an IC or LSI is formed in each of the rectangular regions. The wafer 58 is supported on an annular frame 66 via an adhesive tape 64. In this embodiment, the back surface 58b of the wafer 58 is attached to the adhesive tape 64, but the front surface 58a of the wafer 58 may also be attached to the adhesive tape 64.

[0034] (Processing method) Next, a preferred embodiment of the laser processing method according to the present invention will be described.

[0035] (preparation process) In this embodiment, first, a preparation step is carried out to prepare a laser processing apparatus including a chuck table for holding a workpiece, a laser beam application means for irradiating the workpiece held on the chuck table with a pulsed laser beam, and a feed means for relatively feeding the chuck table and the laser beam application means for processing. The laser processing apparatus prepared in the preparation step may be the above-mentioned laser processing apparatus 2. Therefore, in this specification, a case will be described in which the above-mentioned laser processing apparatus 2 is used to process a wafer 58 as a workpiece.

[0036] (holding process) After the preparation step, a holding step is performed in which the wafer 58 (workpiece) is held on the chuck table 4. In the holding step, the wafer 58 is first placed on the upper surface of the chuck table 4 with the adhesive tape 64 side facing downward and the wafer 58 side facing upward. Next, a suction force is generated in the suction chuck 10 by the suction means, and the wafer 58 is suction-held on the upper surface of the chuck table 4. In addition, the annular frame 66 is fixed with a plurality of clamps 12.

[0037] (Laser beam irradiation process) After the holding step, a laser beam irradiation step is carried out in which the wafer 58 held on the chuck table 4 is irradiated with a pulsed laser beam LB to perform processing.

[0038] In the laser beam application step, first, the focal point of the pulsed laser beam LB is positioned on the dividing line 60 of the wafer 58. At this time, the wafer 58 is imaged by the imaging means 44, and the chuck table 4 is rotated appropriately based on the image of the wafer 58 imaged by the imaging means 44, thereby aligning the dividing line 60 of the wafer 58 in the X-axis direction. Then, the focal point of the pulsed laser beam LB is positioned on the dividing line 60 aligned in the X-axis direction. The vertical position of the focal point can be set as desired.

[0039] Once the focal point of the pulsed laser beam LB is positioned at a desired position, the pulsed laser beam LB is irradiated onto the wafer 58 along the dividing line 60, thereby performing laser processing along the dividing line 60. For example, by irradiating the wafer 58 with a pulsed laser beam LB having a wavelength that is transparent to the wafer 58 from the condenser 38 while feeding the chuck table 4 for processing in the X-axis direction, it is possible to form dividing start points (modified layers or shield tunnels) within the dividing line 60. The shield tunnel is composed of pores extending from the front surface 58a to the back surface 58b of the wafer 58 and an amorphous material surrounding the pores. Note that in the laser beam application step, while feeding the chuck table 4 for processing in the X-axis direction, the pulsed laser beam LB having a wavelength that is absorbed by the wafer 58 is irradiated onto the wafer 58 from the condenser 38, thereby performing ablation processing along the dividing line 60, thereby forming dividing start points.

[0040] Furthermore, the Y-axis feed means 26 indexes and feeds the chuck table 4 in the Y-axis direction by an amount corresponding to the spacing in the Y-axis direction of the planned division lines 60, while repeatedly irradiating the pulsed laser beam LB, thereby performing laser processing on all of the planned division lines 60 aligned in the X-axis direction. Furthermore, the chuck table 4 is rotated 90 degrees, and then irradiation of the pulsed laser beam LB and indexing and feeding are alternately repeated, thereby performing laser processing on all of the planned division lines 60 that are perpendicular to the planned division lines 60 that have been previously laser processed.

[0041] In the laser beam application step, it is important to set the repetition frequency F of the oscillator 36 that oscillates the pulsed laser beam LB to a value equal to or greater than the value obtained by multiplying the thermal conductivity λ [W / (m·K)] of the wafer 58 by a coefficient β [MHz·m·K / W]. However, when the laser beam application means 6 has the oscillator 36b shown in FIG. 4(a), the quasi-repetition frequency Fs, which is the repetition frequency of the packet P, is set to a value equal to or greater than the value obtained by multiplying the thermal conductivity λ [W / (m·K)] of the wafer 58 by a coefficient β [MHz·m·K / W]. This prevents cracks from propagating along the crystalline structure of the wafer 58, even if starting points for division are formed along the planned division lines 60, and prevents damage to the devices 62 during laser processing.

[0042] Furthermore, in the laser beam application process, the repetition frequency F or quasi-repetition frequency Fs is set to a value equal to or greater than the thermal conductivity λ [W / (m·K)] of the wafer 58 multiplied by the coefficient β [MHz·m·K / W], thereby achieving effective heating duration in the wafer 58. Therefore, there is no need to repeatedly attempt processing while adjusting processing conditions such as the output, feed speed, and focal point position of the pulsed laser beam LB, and the desired processing results can be quickly obtained. When the laser beam application means 6 has the oscillator 36b shown in FIG. 4(a), the heating duration in the wafer 58 can be further adjusted by adjusting the quasi-pulse width τ of the packet P, thereby achieving even more effective processing results.

[0043] As described above, in this embodiment, the repetition frequency F of the oscillator 36 that oscillates the pulsed laser beam LB is set to a value equal to or greater than the value obtained by multiplying the thermal conductivity λ [W / (m·K)] of the wafer 58 by the coefficient β [MHz·m·K / W]. This prevents damage to the device 62 during laser processing, and enables desired processing results to be obtained for various workpieces.

[0044] <Experiment> The inventors conducted experiments in which a pulsed laser beam was irradiated onto wafers made of various materials while changing the coefficient β in order to find the coefficient β that would allow proper laser processing to be performed by irradiating a wafer with a pulsed laser beam. The pulsed laser beam conditions and the wafers that were laser processed were as follows:

[0045] <Conditions for pulsed laser beam> Wavelength: 1064nm Average power: 1W

[0046] <Wafer> Material Thermal conductivity λ [W / (m K)] Thickness [μm] Quartz 1.4 700 Sapphire 42 700 SiC 490 700 Diamond 2000 700

[0047] The results of laser processing on each of the above wafers are as follows: "OK" in the following evaluation indicates that the crack did not propagate in accordance with the crystalline structure of the wafer, and the starting point for division was successfully formed along the planned dividing line. On the other hand, "NG" in the following evaluation indicates that the crack propagated in accordance with the crystalline structure of the wafer, and the starting point for division was not successfully formed along the planned dividing line.

[0048] <Experimental result 1: Quartz wafer, λ=1.4> Coefficient β [MHz m K / W] Repetition frequency [MHz] Judgment 1.0 1.4 OK 0.5 0.7 OK 0.3 0.42 OK 0.2 0.28 OK 0.15 0.21 NG 0.1 0.14 NG

[0049] <Experimental result 2: Sapphire wafer, λ=42> Coefficient β [MHz m K / W] Repetition frequency [MHz] Judgment 1.0 42 OK 0.5 21 OK 0.3 12.6 OK 0.2 8.4 OK 0.15 6.3 NG 0.1 4.2 NG

[0050] <Experimental result 3: SiC wafer, λ=490> Coefficient β [MHz m K / W] Repetition frequency [MHz] Judgment 1.0 490 OK 0.5 245 OK 0.3 147 OK 0.2 98 OK 0.15 73.5 NG 0.1 49 NG

[0051] <Experimental result 4: Diamond wafer, λ=2000> Coefficient β [MHz m K / W] Repetition frequency [MHz] Judgment 1.0 2000 OK 0.5 1000 OK 0.3 600 OK 0.2 400 OK 0.15 300 NG 0.1 200 NG

[0052] From the above experimental results 1 to 4, it was confirmed that when the coefficient β is 0.2 or more, good laser processing can be performed regardless of whether the wafer material is quartz, sapphire, SiC, or diamond. Although the description of the experimental results is omitted, the inventors have confirmed that a similar tendency is observed in single crystal wafers formed from materials such as lithium tantalate (LT), lithium niobate (LN), and gallium nitride (GaN). [Explanation of symbols]

[0053] 2: Laser processing equipment 4: Chuck table 6: Laser beam irradiation means 8:Feeding means 36: Oscillator 38: Concentrator 52: Packet setting section 54: Quasi-repetition frequency setting unit 56: Power amplifier

Claims

1. A laser processing apparatus including a chuck table for holding a workpiece, a laser beam application means for applying a pulsed laser beam to the workpiece held on the chuck table, and a feed means for relatively feeding the chuck table and the laser beam application means for processing, the laser beam application means includes an oscillator that oscillates a pulsed laser beam, and a condenser that condenses the pulsed laser beam oscillated by the oscillator and irradiates the workpiece held on the chuck table with the condensed laser beam; A laser processing device in which the repetition frequency of the pulsed laser beam oscillated by the oscillator is set to a value equal to or greater than the thermal conductivity λ [W / (m·K)] of the workpiece multiplied by a coefficient β [MHz·m·K / W].

2. 2. The laser processing device according to claim 1, wherein the coefficient β is 0.

2.

3. The oscillator comprises a packet setting unit that sets a packet, each group consisting of an arbitrary number of pulsed laser beams, a quasi-repetition frequency setting unit that sets a quasi-repetition frequency for thinning out the pulsed laser beam between the packet and an adjacent packet, and a power amplification unit that amplifies the power of the pulsed laser beam, 2. The laser processing apparatus according to claim 1, wherein the packet adjusts the duration of heating on the workpiece.

4. A method for laser processing a workpiece, comprising: a preparation step of preparing a laser processing device including a chuck table for holding a workpiece, a laser beam application means for applying a pulsed laser beam to the workpiece held on the chuck table, and a feed means for relatively feeding the chuck table and the laser beam application means for processing; a holding step of holding a workpiece on the chuck table; a laser beam application step of applying a pulsed laser beam to the workpiece held on the chuck table to process the workpiece, In the laser beam irradiation step, the repetition frequency of the oscillator that oscillates the pulsed laser beam is set to a value equal to or greater than the thermal conductivity λ [W / (m·K)] of the workpiece multiplied by a coefficient β [MHz·m·K / W].

Images