Laser processing method

Abstract

To provide a laser processing method in which attachment of debris to a workpiece is restricted.SOLUTION: In a laser processing method, a workpiece is irradiated with a laser beam in processing the workpiece. The laser processing method includes: a holding step 1 for holding a workpiece in a processing chamber such that one surface side of the workpiece is directed vertically downward; a vacuuming step 2 for reducing a pressure of air inside the processing chamber to a prescribed pressure being lower than ambient pressure, after the holding step 1; and a laser irradiating step 3 for irradiating one surface side of the workpiece with a laser beam, after the vacuuming step 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In general, in device manufacturing, a number of streets (planned division lines) arranged in a grid pattern are set on the surface of a substrate such as a wafer, such as a semiconductor wafer or an optical device wafer, and devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integrations) are formed in a number of chip areas partitioned by the streets.

[0003] As a method for dividing a wafer along the streets, a method has been proposed in which a laser beam of a wavelength that is absorbent for the wafer is irradiated along the intended dividing line to perform ablation processing, thereby forming a laser processed groove that serves as the starting point for dividing (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-305420 Summary of the Invention [Problem to be solved by the invention]

[0005] However, ablation processing has the problem that fine dust called debris is generated when the laser beam is irradiated. This dust is scattered into the processing chamber and accumulates on the surface of the device, reducing the quality of the device.

[0006] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a laser processing method capable of suppressing adhesion of debris to a workpiece. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the laser processing method of the present invention is a laser processing method for processing a workpiece by irradiating the workpiece with a laser beam, and is characterized in that it includes a holding step of holding the workpiece in a processing chamber so that one side of the workpiece faces vertically downward, a vacuum step after the holding step of reducing the air pressure in the processing chamber to a predetermined pressure lower than atmospheric pressure, and a laser irradiation step after the vacuum step of irradiating the one side of the workpiece with the laser beam.

[0008] In the laser processing method of the present invention, the workpiece may be a silicon substrate, and in the laser irradiation step, a fluorine-based gas may be supplied to the one surface side of the workpiece irradiated with the laser beam. Effect of the Invention

[0009] The present invention can suppress adhesion of debris to a workpiece. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a flowchart showing the flow of a laser processing method according to an embodiment. [Diagram 2] FIG. 2 is a perspective view showing an example of a workpiece to be processed. [Diagram 3] FIG. 3 is a schematic diagram showing an example of the configuration of a laser processing apparatus for carrying out the laser processing method according to the embodiment. [Figure 4] FIG. 4 is a schematic diagram showing a laser processing apparatus for carrying out the laser processing method according to the first modified example. [Diagram 5] FIG. 5 is a schematic diagram showing a laser processing apparatus for carrying out a laser processing method according to the second modified example. [Figure 6] FIG. 6 is a schematic diagram showing a laser processing apparatus for carrying out a laser processing method according to a third modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The form (embodiment) 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 embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0012] [Embodiment] A laser processing method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart showing the flow of the laser processing method according to the embodiment. FIG. 2 is a perspective view showing an example of a workpiece 10 to be processed. FIG. 3 is a schematic diagram showing a configuration example of a laser processing device 20 that performs the laser processing method according to the embodiment. The laser processing method according to the embodiment includes a holding step 1, a vacuuming step 2, and a laser irradiation step 3, and is performed in the laser processing device 20 shown in FIG. 3 with the workpiece 10 shown in FIG. 2 as the processing object.

[0013] First, an example of the workpiece 10 to be processed will be described. The workpiece 10 is, for example, a disk-shaped semiconductor wafer, an optical device wafer, or other wafer, with silicon (Si), silicon carbide (SiC), gallium nitride (GaN), gallium arsenide (GaAs), or other semiconductor material as the substrate 11. Alternatively, the workpiece 10 is a disk-shaped wafer with sapphire (Al2O3), glass, quartz, or other material as the substrate 11. Examples of glass include alkali glass, non-alkali glass, soda-lime glass, lead glass, borosilicate glass, quartz glass, and the like. The workpiece 10 of the embodiment is a silicon substrate.

[0014] 2, the workpiece 10 has a plurality of planned division lines 13 set in a grid pattern on the surface 12 of the substrate 11, and devices 14 formed in areas partitioned by the planned division lines 13. The devices 14 are, for example, integrated circuits such as ICs or LSIs, image sensors such as CCDs (Charge Coupled Devices) or CMOSs ​​(Complementary Metal Oxide Semiconductors), or MEMS (Micro Electro Mechanical Systems).

[0015] The workpiece 10 may be transported and processed in a state where, for example, an annular frame is attached and a tape having a diameter larger than the outer diameter of the workpiece 10 is attached to the back surface 15 of the workpiece 10 and supported within an opening of the frame. The workpiece 10 is divided into individual devices 14 along the planned division lines 13 and singulated into device chips 16. Note that the workpiece 10 is not limited to a disk shape, and may be other plate shapes such as a resin package substrate or a metal substrate. Also, the device chips 16 are not limited to a square shape, and may be rectangular or polygonal.

[0016] Next, an example of a laser processing device 20 that performs laser processing on a workpiece 10 will be described. As shown in Fig. 3, the laser processing device 20 includes a processing chamber 21, a holding unit 30, a moving unit 40, and a laser irradiation unit that irradiates a laser beam 50. In the following description, the X-axis direction is one direction on a horizontal plane and is the processing feed direction. The Y-axis direction is a direction perpendicular to the X-axis on the horizontal plane and is the indexing feed direction. The Z-axis direction is a direction perpendicular to the X-axis and Y-axis directions and is the focal point position adjustment direction.

[0017] The processing chamber 21 houses a holding unit 30 and a moving unit 40. The processing chamber 21 can form an internal space 22 that is isolated from the outside. A load / unload port (not shown) that can be opened and closed for loading and unloading the workpiece 10, a window 23, and an exhaust port 24 are formed in the wall that partitions the processing chamber 21.

[0018] The window portion 23 is formed in the floor portion on the lower surface side of the wall portion that divides the processing chamber 21. The window portion 23 is formed on the optical path of a laser beam 50 that is irradiated vertically upward from the outside of the processing chamber 21 toward the holding surface 31 of the holding unit 30, and transmits the laser beam 50. The window portion 23 is made of, for example, BK7 (borosilicate crown glass), CaF2 (calcium fluoride), or SiO2 (synthetic quartz glass).

[0019] The exhaust port 24 is formed in one of the walls that divide the processing chamber 21, and in the example shown in Fig. 3, it is formed at a position close to the floor surface on the left side of the drawing. The exhaust port 24 is connected to a vacuum suction source (not shown) via an exhaust path 25. When the processing chamber 21 is in a sealed state, the vacuum suction source (not shown) creates a negative pressure, thereby reducing the pressure in the space 22.

[0020] The holding unit 30 is a unit that holds the workpiece 10 so that one surface (front surface 12 in the embodiment) of the workpiece 10 faces vertically downward. The holding unit 30 in the embodiment is a holding table having a holding surface 31 that is a plane parallel to the horizontal direction and faces vertically downward. The holding unit 30 in the embodiment is provided with an electrode 32 connected to a high-frequency power source (not shown).

[0021] In the holding unit 30, when power is applied to the electrode 32 from the high frequency power source, a dielectric polarization phenomenon occurs between the holding surface 31 and the workpiece 10, and the workpiece 10 is attracted and held on the holding surface 31 by electrostatic attraction force due to polarization of the electric charge. The holding unit 30 in the embodiment attracts and holds the back surface 15 side of the workpiece 10 on the holding surface 31, and exposes the front surface 12 side downward.

[0022] The moving unit 40 is a unit that relatively moves the holding unit 30 and the focal point 51 of the laser beam 50. The moving unit 40 includes a processing feed unit 41, an indexing feed unit 42, a focal point position adjustment unit (not shown), and a rotation unit 43.

[0023] The processing feed unit 41 is a unit that relatively moves the holding unit 30 and the focal point 51 of the laser beam 50 in the X-axis direction, which is the processing feed direction. In the embodiment, the processing feed unit 41 moves the holding unit 30 and the rotating unit 43 in the X-axis direction. The processing feed unit 41 is provided so as to be movable in the Y-axis direction by, for example, the indexing feed unit 42.

[0024] The indexing feed unit 42 is a unit that relatively moves the holding unit 30 and the focal point 51 of the laser beam 50 in the Y-axis direction, which is the indexing feed direction. In the embodiment, the indexing feed unit 42 moves the holding unit 30, the rotation unit 43, and the processing feed unit 41 in the Y-axis direction. The indexing feed unit 42 is installed on the ceiling wall of the processing chamber 21, for example.

[0025] The focal point position adjustment unit (not shown) is a unit that moves at least the condenser 52 in the Z-axis direction, which is the focal point position adjustment direction, among the laser irradiation units that irradiate the laser beam 50. In the embodiment, the focal point position adjustment unit moves the condenser 52 in the Z-axis direction relative to the processing chamber 21.

[0026] The rotation unit 43 is a unit that rotates the holding unit 30 around an axis parallel to the Z-axis direction. In the embodiment, the rotation unit 43 rotates the holding unit 30 around the axis relative to the processing feed unit 41.

[0027] The laser irradiation unit that irradiates the laser beam 50 includes, for example, a laser oscillator (not shown), a condenser 52, and various optical components that guide the laser beam 50 from the laser oscillator to the condenser 52. The laser oscillator emits the laser beam 50 having a predetermined wavelength for processing the workpiece 10. The condenser 52 condenses the laser beam 50 emitted from the laser oscillator and irradiates it toward the workpiece 10 held on the holding surface 31 of the holding unit 30. The laser beam 50 that has passed through the condenser 52 is irradiated toward the holding unit 30 through the window portion 23.

[0028] Next, each step of the laser processing method of the embodiment will be described in detail. Holding step 1 shown in Fig. 1 is a step of holding the workpiece 10 in the processing chamber 21 so that one surface (front surface 12 in the embodiment) of the workpiece 10 faces vertically downward as shown in Fig. 3. Specifically, the workpiece 10 is transported to a holding unit 30 inside the processing chamber 21 by a transport unit (not shown) or the like with the back surface 15 facing upward.

[0029] Next, with the back surface 15 of the workpiece 10 in contact with the holding surface 31 of the holding unit 30, power is applied to the electrode 32 from a high frequency power source (not shown), causing a dielectric polarization phenomenon between the holding surface 31 and the workpiece 10, and the back surface 15 of the workpiece 10 is attracted and held on the holding surface 31 by electrostatic attraction force due to polarization of the charge. The holding unit 30 attracts and holds the back surface 15 of the workpiece 10 on the holding surface 31, exposing the front surface 12 downward.

[0030] The evacuation step 2 shown in FIG. 1 is carried out after the holding step 1. The evacuation step 2 is a step for reducing the air pressure in the processing chamber 21 shown in FIG. 3 to a predetermined pressure lower than atmospheric pressure. Specifically, first, the unillustrated loading / unloading port used for transporting the workpiece 10 into the processing chamber 21 in the holding step 1 is closed, and the space 22 inside the processing chamber 21 is sealed. Next, a vacuum suction source (not shown) is operated to reduce the pressure in the space 22 via the exhaust port 24 and exhaust path 25. At this time, the space 22 is depressurized to a pressure of 1×10 4The pressure is reduced to 100 MPa (absolute pressure) or less, and the lower the pressure the more preferable.

[0031] The laser irradiation step 3 shown in Fig. 1 is carried out after the evacuation step 2. The laser irradiation step 3 is a step of irradiating a laser beam 50 onto one surface (in the embodiment, the front surface 12) of the workpiece 10 facing vertically downward, as shown in Fig. 3. In the embodiment, the laser beam 50 is a laser beam having a wavelength that is absorbed by the workpiece 10. Here, a case will be described in which the laser beam 50 is linearly irradiated in the processing feed direction to perform linear groove processing along the intended division line 13 (see Fig. 2), but the present invention may also be applied to, for example, annular groove processing.

[0032] Specifically, first, the planned division lines 13 are detected by, for example, capturing an image of the surface 12 of the workpiece 10 with an imaging unit (not shown). Next, the holding unit 30 is rotated around the Z axis by the rotating unit 43 to match the direction in which the planned division lines 13 to be processed extend with the processing feed direction (X-axis direction). In addition, the processing feed unit 41 and the indexing feed unit 42 position the processing start position of the planned division lines 13 at a position where the laser beam 50 is irradiated, and a focal point position adjustment unit (not shown) sets the focal point 51 of the laser beam 50 near the surface 12 of the workpiece 10.

[0033] Next, while irradiating the pulsed laser beam 50, the processing feed unit 41 moves the holding unit 30 in the processing feed direction (X-axis direction) at a predetermined feed rate. As a result, a processing groove is formed along the division lines 13 on the surface 12 of the workpiece 10. Next, the indexing feed unit 42 moves the holding unit 30 a predetermined distance in the indexing feed direction (Y-axis direction), and adjacent division lines 13 are positioned to be irradiated with the laser beam 50, and laser processing is performed in the same manner. After processing all the division lines 13 along one direction, the division lines 13 perpendicular to one direction are similarly positioned to be irradiated with the laser beam 50 and laser processing is performed, thereby forming laser processing grooves on all the division lines 13.

[0034] As described above, in the laser processing method according to the embodiment, the workpiece 10, which has one surface (front surface 12) to be processed facing vertically downward, is irradiated with the laser beam 50 from below to above in a vacuum to perform processing. Here, the reason why debris adheres to the workpiece 10 by irradiation with the laser beam 50 is considered to be that the debris scattered by the expansion of the air near the processing point falls due to gravity, and the expanded air cools and contracts, returning to the processing point.

[0035] Falling of debris due to gravity can be prevented by holding the surface (front surface 12) of the workpiece 10 to be processed vertically during laser processing. Contraction of the expanded air can be prevented by creating a vacuum state in the space 22 in the processing area. Therefore, the laser processing method of the embodiment can suppress adhesion of debris to the workpiece 10.

[0036] Therefore, even if the workpiece 10 is not covered with a protective film of liquid resin that transmits the laser beam 50 as in the conventional method, it is possible to prevent debris from adhering to the workpiece 10, and it is possible to reduce the time required for the process of removing the liquid resin and the cost of the liquid resin, which cannot be reused. Furthermore, by using a protective film of liquid resin in addition to the method of the embodiment, it is possible to further prevent debris from adhering to the workpiece 10.

[0037] [First Modification] Next, a laser processing method according to a first modified example will be described with reference to the drawings. Fig. 4 is a schematic diagram showing a laser processing apparatus 20-1 for carrying out the laser processing method according to the first modified example. In the laser processing apparatus 20-1 used in the first modified example, the same components as those in the laser processing apparatus 20 of the embodiment are denoted by the same reference numerals and will not be described.

[0038] In the laser processing method of the first modification, the workpiece 10 to be processed is limited to a silicon substrate. In the laser processing method of the first modification, in the laser irradiation step 3, the laser beam 50 is irradiated while a fluorine-based gas 60 is being supplied to one surface (front surface 12 in the first modification) of the workpiece 10 to be irradiated with the laser beam 50. The fluorine-based gas 60 includes, for example, sulfur hexafluoride (SF6) gas, carbon tetrafluoride (CF4) gas, nitrogen trifluoride (NF3) gas, and the like.

[0039] The laser processing apparatus 20-1 used in the first modified example differs from the laser processing apparatus 20 of the embodiment in that it includes a gas supply nozzle 61 that supplies a fluorine-based gas 60. The gas supply nozzle 61 has an injection port inside the processing chamber 21, and supplies the fluorine-based gas 60 toward the focal point 51 of the laser beam 50, i.e., the processing point. In the first modified example, the gas supply nozzle 61 is disposed in a position adjacent to the window portion 23 on the floor of the processing chamber 21.

[0040] As described above, in the laser processing method according to the first modification, the laser beam 50 is irradiated while the fluorine-based gas 60 is being supplied to the processing point. The fluorine-based gas 60 is decomposed in plasma generated by the irradiation of the laser beam 50. Silicon fluoride is generated in a gaseous state by a reaction between fluorine decomposed from the fluorine-based gas 60 and silicon particles, which are debris generated from the workpiece 10. This makes it possible to suppress the debris from reattaching to the workpiece 10.

[0041] In addition to the embodiment of the first modified example, when the fluorine-based gas 60 is supplied, the fluorine-based gas 60 may be converted into plasma between the gas supply nozzle 61 and the workpiece 10 held in the holding unit 30, and plasma etching may be performed simultaneously with the laser processing in the laser irradiation step 3.

[0042] In this case, for example, the processing chamber 21 is treated as a chamber of a plasma etching device, and a pair of electrodes are arranged vertically facing each other between the holding unit 30 and the lower part of the processing chamber 21. The pair of electrodes are made of a conductive material, insulated from the processing chamber 21, and connected to a high-frequency power source. By applying power from the high-frequency power source to the pair of electrodes, the fluorine-based gas 60 is turned into plasma, and is drawn into the workpiece 10 held by the holding unit 30. As a result, the portion of one side (surface 12 in this embodiment) of the workpiece 10 that has been melted by irradiation with the laser beam 50 can be removed by plasma etching.

[0043] [Second Modification] Next, a laser processing method according to a second modified example will be described with reference to the drawings. Fig. 5 is a schematic diagram showing a laser processing apparatus 20-2 for carrying out the laser processing method according to the second modified example. In the laser processing apparatus 20-1 used in the second modified example, the same components as those in the laser processing apparatus 20-1 of the first modified example are denoted by the same reference numerals and will not be described.

[0044] In the laser processing method of the second modification, fluorine-based gas 60 is supplied coaxially with the optical path of laser beam 50 while surrounding the optical path. Laser processing apparatus 20-2 used in the second modification has a different configuration of condenser 52-1 and gas supply nozzle 61-1 from the configurations of condenser 52 and gas supply nozzle 61 of laser processing apparatus 20-1 of the first modification, and also differs in that enclosure 26 is provided.

[0045] The collector 52-1 of the second modification is disposed inside the processing chamber 21. That is, the laser beam 50 is incident on the collector 52-1 after passing through the window 23 and is collected. The gas supply nozzle 61-1 is provided on the floor of the processing chamber 21. The gas supply nozzle 61-1 has a plurality of nozzles arranged in a ring shape or an annular opening so as to surround the window 23 through which the laser beam 50 passes. The enclosure 26 is provided in a truncated cone shape from the floor of the processing chamber 21 upward so as to surround the gas supply nozzle 61-1 and the optical path of the laser beam 50 from the side. The fluorine-based gas 60 supplied from the gas supply nozzle 61-1 fills the inside of the truncated cone-shaped enclosure 26 and is supplied from the opening 27 at the top end of the truncated cone shape toward the focal point 51 of the laser beam 50, i.e., the processing point.

[0046] As described above, in the laser processing method according to the second modification, when the fluorine-based gas 60 is supplied to the focal point 51 of the laser beam 50, the enclosure 26 is formed to surround the optical path of the laser beam 50. As in the first modification, this has the effect of suppressing re-adhesion of debris, which is silicon fine particles, to the workpiece 10 due to a reaction between fluorine and the debris, and also has the effect of suppressing contamination of the window 23 and the collector 52-1 on the inner side of the processing chamber 21 by debris.

[0047] [Third Modification] Next, a laser processing method according to a third modified example will be described with reference to the drawings. Fig. 6 is a schematic diagram showing a laser processing apparatus 20-3 for carrying out the laser processing method according to the third modified example. In the laser processing apparatus 20-3 used in the third modified example, the same components as those in the laser processing apparatus 20 of the embodiment are denoted by the same reference numerals and will not be described.

[0048] The laser processing apparatus 20-3 used in the third modification is different from the laser processing apparatus 20 of the embodiment in that the configurations of the processing chamber 21-1 and the moving unit 40-1 are different from those of the processing chamber 21 and the moving unit 40 of the laser processing apparatus 20 of the embodiment.

[0049] The machining chamber 21-1 of the third modified example can be moved in the X-axis direction, which is the machining feed direction, and in the Y-axis direction, which is the index feed direction, by the machining feed unit 41-1 and the index feed unit 42-1 of the moving unit 40-1. The machining feed unit 41-1 is provided outside the machining chamber 21-1 and moves the machining chamber 21-1 in the X-axis direction. The index feed unit 42-1 moves the machining chamber 21-1 and the machining feed unit 41-1 in the Y-axis direction.

[0050] The rotating unit 43-1 is provided inside the processing chamber 21-1, and rotates the holding unit 30 about its axis relative to the processing chamber 21-1. In this way, in the third modified example, the entire processing chamber 21-1 moves relative to the focusing point 51 of the laser beam 50. That is, since the positions of the processing chamber 21-1 and the focusing device 52 move relatively, the window portion 23-1 that transmits the laser beam 50 from the outside to the inside of the processing chamber 21-1 is formed on almost the entire surface of the floor of the processing chamber 21-1 accordingly.

[0051] As described above, in the laser processing method according to the third modified example, the processing chamber 21-1 is processed and indexed. That is, since the holding unit 30 is fixed to the processing chamber 21-1 in the translational direction, the dimensions of the processing chamber 21-1 can be reduced. Therefore, for example, it is easy to reduce the pressure of the space 22 inside the processing chamber 21-1.

[0052] The present invention is not limited to the above embodiment and modified examples. In addition, the configurations of the embodiment and each modified example may be partially interchangeable with each other. For example, the configuration in which the processing feed unit 41-1 and the indexing feed unit 42-1 of the third modified example are provided outside the processing chamber 21-1 may be applied to the laser processing apparatuses 20-1 and 20-2 of the first and second modified examples. In addition, in the embodiment, the first and third modified examples, the condenser 52-1 may be disposed inside the processing chamber 21 and 21-1 from the window portion 23 and 23-1, and in the second modified example, the condenser 52 may be disposed outside the processing chamber 21 from the window portion 23.

[0053] Furthermore, in the above embodiment and modified examples, the holding unit 30 attracts and holds the workpiece 10 by electrostatic adsorption force, but when processing the workpiece 10 while supported by a frame and tape as described above, multiple clamp members may be arranged around the holding unit 30, and the clamp members may clamp the frame to hold the workpiece 10.

[0054] Furthermore, the method of processing and feeding the focal point 51 of the laser beam 50 is not limited to the processing and feeding units 41 and 41-1 of the embodiment and the modified example, and may be by scanning the laser beam 50. That is, the laser irradiation unit that irradiates the laser beam 50 may have a scanning unit such as a polygon mirror or a galvanometer mirror having an axis parallel to the Y-axis direction. In this case, the condenser 52 and 52-1 include an fθ lens that is a composite lens made up of a combination of multiple lenses. [Explanation of symbols]

[0055] 1 Hold Step 2 Vacuum Step 3 Laser irradiation step 10 Workpiece 11 Substrate 12 Surface (one side) 13 Division line 14 Devices 15 Back side 16 Device Chips 20, 20-1, 20-2, 20-3 Laser processing equipment 21, 21-1 Processing room 22 Space 23, 23-1 Window section 24 Exhaust port 25 Exhaust duct 26 Enclosure 27 Aperture 30 Holding Unit 31 Holding surface 32 electrodes 40, 40-1 Mobile unit 41, 41-1 Processing feed unit 42, 42-1 Indexing feed unit 43, 43-1 Rotating unit 50 Laser Beam 51 Focus point 52, 52-1 Concentrator 60 Fluorine-based gases 61, 61-1 Gas supply nozzle

Claims

1. A laser processing method for processing a workpiece by irradiating the workpiece with a laser beam, comprising: a holding step of holding the workpiece in the processing chamber so that one surface of the workpiece faces vertically downward; a vacuum step of reducing the air pressure in the processing chamber to a predetermined pressure lower than atmospheric pressure after the holding step; a laser irradiation step of irradiating the one surface side of the workpiece with the laser beam after the evacuation step; Equipped A laser processing method comprising:

2. the workpiece is a silicon substrate, In the laser irradiation step, a fluorine-based gas is supplied to the one surface side of the workpiece to be irradiated with the laser beam.

2. The laser processing method according to claim 1.

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