Laser cutting device and method

Abstract

A laser cutting device and method are provided that can cut a workpiece having thermal brittleness to a desired thickness. [Solution] The cutting device of the present invention includes a laser generating unit that generates a laser beam that passes through the surface of the workpiece and is only partially absorbed; a beam generating optical unit that focuses the laser beam into a shape that is parallel to the surface of the workpiece to the depth at which it is intended to cut on the surface of the workpiece and extends perpendicular to the cutting direction, generating a laser beam that heats the workpiece to a temperature below its melting point so as not to melt the cut surface and that will generate internal stress that will separate the cut location in the workpiece; and a start point generating unit that generates damage at the cut start point on the outer edge of the cut surface at which it is intended to cut the workpiece.By providing a configuration that cuts the workpiece without melting it and with reduced damage, it is possible to cut a workpiece that has thermal brittleness to a desired thickness using a slice method.

Description

[Technical Field]

[0001] The present invention relates to a laser cutting device and method, and more particularly to a laser cutting device and method for irradiating a laser beam onto an object having thermal brittleness, such as a glass or ceramic ingot, and cutting it in a slicing manner. [Background technology]

[0002] The wafer slicing process is a process in which a silicon ingot in the shape of a block is cut into the shape of a wafer that is normally used.

[0003] Such wafer slicing processes include an ID (Inner Diamond) sawing method, a wire sawing method, and a laser cutting method.

[0004] For example, Patent Documents 1 and 2 below each disclose a cutting method using a wire and a laser.

[0005] Meanwhile, the process of cutting objects with thermal brittleness, such as wafers, ceramics, and glass, has been problematic in that it results in a large number of defects due to cracks and thermal damage, resulting in low yields and excessive loss of processed objects such as ingots.

[0006] In particular, the process of processing an ingot into a wafer involves not only a wafer cutting process but also a number of additional processes such as an ingot and wafer grinding process, which reduces workability and reduces production efficiency. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent Publication No. 10-2008-0001394 [Patent Document 2] Korean Patent No. 10-2368338 Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is to solve the above problems and to provide a laser cutting device and method that can cut workpieces having thermal brittleness, such as glass, ceramics, and ingots, to a desired thickness using a slicing method.

[0009] Another object of the present invention is to provide a laser cutting apparatus and method that can irradiate a workpiece with a laser beam to heat and cool it, thereby cutting the workpiece without melting or vaporizing it. [Means for solving the problem]

[0010] In order to achieve the above object, a cutting device using a laser according to the present invention includes a laser generating unit that generates a laser beam that penetrates the surface of a workpiece and is only partially absorbed; a beam generating optical unit that focuses the laser beam into a shape that extends parallel to the surface of the workpiece and perpendicular to the cutting direction at a depth to be cut in the surface of the workpiece, thereby generating a laser beam that heats the workpiece to a temperature below its melting point so as not to melt the cut surface of the workpiece and to a temperature that generates internal stress that separates the cut portion in the workpiece; and an initiation point generating unit that generates damage at a cut initiation point on the outer periphery of the cut surface to be cut in the workpiece, thereby cutting the workpiece in a slice manner without melting it and reducing damage.

[0011] In order to achieve the above object, the cutting method using a laser beam according to the present invention includes the steps of: (a) generating a laser beam in a laser generating unit that passes through the surface of the workpiece and is only partially absorbed; (b) using a start point generating unit to generate damage at a cutting start point on the outer periphery of the cutting surface to be cut in the workpiece; and (c) using a beam generating optical unit to focus the laser beam into a shape that extends parallel to the surface of the workpiece and perpendicular to the cutting direction at the depth to be cut in the surface of the workpiece, and generating and irradiating the laser beam that heats the cutting surface of the workpiece to a temperature below its melting point so as not to melt it, but to generate internal stress that separates the cutting point from the workpiece, thereby cutting the workpiece in a slicing manner without melting it and reducing damage. [Effects of the Invention]

[0012] According to the laser cutting device and method of the present invention, a workpiece having thermally brittle properties can be cut into slices to a desired thickness.

[0013] Furthermore, according to the present invention, the workpiece can be cut with minimal damage by irradiating the workpiece with a laser beam to heat and cool it without melting or vaporizing it.

[0014] Furthermore, according to the present invention, the cut portion can be easily separated from the object by using the separating portion, and the flatness of the cut surface can be improved.

[0015] As a result, according to the present invention, the workability of the cutting operation of the workpiece can be improved, and post-processing of the cut portion, such as a polishing process performed during wafer manufacturing, can be eliminated or minimized, thereby maximizing productivity. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram illustrating the configuration of a cutting device using a laser according to the present invention. [Figure 2]FIG. 2 is a block diagram of a cutting device using a laser in FIG. 1. [Figure 3] FIG. 2 is a diagram illustrating a configuration of a separation unit. [Figure 4] FIG. 2 is a diagram illustrating a configuration of a separation unit. [Figure 5] FIG. 2 is a diagram showing the arrangement of a cooling unit and a laser generating unit. [Figure 6] FIG. 2 is a diagram showing the arrangement of a cooling unit and a laser generating unit. [Figure 7] FIG. 2 is a diagram showing the arrangement of a cooling unit and a laser generating unit. [Figure 8] 1 is a flowchart illustrating a step-by-step method for cutting using a laser according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a laser cutting apparatus and method according to preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0018] FIG. 1 is a diagram showing the configuration of a cutting device using a laser according to a preferred embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of the cutting device using the laser shown in FIG.

[0019] Hereinafter, terms indicating directions such as "left side," "right side," "front," "rear," "upper side," and "lower side" are defined as indicating the respective directions based on the state in each drawing.

[0020] In this embodiment, the configuration of a cutting apparatus that cuts an ingot into wafers of a predetermined thickness by slicing will be described.

[0021] However, the present invention is not limited to this, and can be applied not only to cutting devices that cut ingots to process wafers, but also to cutting devices that cut workpieces that have thermal brittleness properties, such as glass and ceramics.

[0022] Furthermore, the present invention can be applied to cutting devices that cut not only silicon wafers but also high-hardness, high-brittle materials such as silicon carbide (SiC) wafers and gallium nitride (GaN) wafers, which are harder than silicon wafers.

[0023] As shown in Figures 1 and 2, a laser cutting device 10 according to a preferred embodiment of the present invention includes a laser generating unit 20 that generates a laser beam 21 that passes through the surface of the workpiece 11 and is only partially absorbed; a beam generating optical unit 30 that focuses the laser beam 21 into a shape that is parallel to the surface of the workpiece 11 at the depth at which the workpiece 11 is to be cut and extends perpendicular to the cutting direction, thereby generating the laser beam 21 that heats the workpiece 11 to a temperature below its melting point so as not to melt the cut surface, but which generates internal stress that separates the cut point 14 from the workpiece 11; and an initiation point generating unit 50 that generates damage at a cut initiation point 13 on the outer periphery of the cut surface 12 at which the workpiece 11 is to be cut, thereby cutting the workpiece without melting it and with reduced damage.

[0024] In addition, the laser cutting device 10 according to a preferred embodiment of the present invention further includes a cooling section 40 that supplies a coolant to the cutting point 14 heated by the laser beam 21 to cool it, a separation section 60 that separates the cut cutting point 14 from the workpiece 11, and a control section 70 that controls the operation of each device.

[0025] The control unit 70 can control the diameter of the workpiece 11, for example, an ingot, the thickness of the object to be cut, i.e., the cutting depth based on the top surface of the ingot, the intensity of the laser beam 21 irradiated by the laser generating unit 20, the cutting speed at which the ingot is cut by moving the laser beam along the cutting direction, and the cooling speed determined by the amount and speed of coolant sprayed by the cooling unit 30.

[0026] For example, the control unit 70 can generate a control signal that changes the laser beam 21 to have various shapes and energy distributions according to the diameter and cutting depth of the ingot, the cutting speed, and the cooling speed, and automatically adjusts the output of the laser beam 21 in proportion to the cutting speed.

[0027] The laser generating unit 20 can be provided as a beam generator that generates a laser beam 21, and the beam generating optical unit can be provided as a lens unit that adjusts the focus of the laser beam 21 generated by the beam generator in accordance with the cutting depth and irradiates the workpiece 11 with the laser beam.

[0028] Generally, an ingot is formed in a roughly cylindrical shape and can be cut into a predetermined thickness, i.e., a shape in which the ingot is upright in the vertical direction, by a slicing method using a laser beam 21 that is irradiated so that the focus is positioned at a predetermined cutting depth based on the top surface of the ingot.

[0029] 1, the laser beam 21 irradiated to the workpiece 11 moves along the X-axis direction from the damage generated at the cut starting point 13 located on the outer periphery of the cut surface 12. The laser beam 21 can then cut the cut location 14 on the top surface of the workpiece 11 to a thickness corresponding to the cut depth along the −Z-axis direction.

[0030] That is, laser beam 21 is a linear line beam that extends long along the Y-axis direction so as to be perpendicular to cutting surface 13 that is parallel to the upper surface of workpiece 11.

[0031] For example, the laser beam 21 has a wavelength of about 1×10 -3 μm~1×10 -2 μm wavelength and approximately 1×10 -2 mW / mm 2 ~1×10 5 mW / mm 2 It has an energy density of about 1×10 -2 mm / s~1×10 4 It can move at a speed of mm / s.

[0032] In Figure 1, the position of the laser beam 21 focused to cut the workpiece 11 is slightly away from the actual cutting line on the cutting surface 12, which is the right edge in Figure 1. This is because the workpiece 11 is cut at the position where coolant is supplied after being irradiated with the laser beam 21, resulting in a gap between the position of the laser beam and the actual cutting line. The stronger the intensity of the laser beam 21, the narrower the gap between the laser beam 21 and the cutting line, and the weaker the intensity of the laser beam 21, the wider the gap.

[0033] In this manner, in this embodiment, the laser generating unit 20 sets the output of the laser beam 21 so that the workpiece 11 is heated to a temperature below the melting point at which the cut surface 13 of the workpiece 11 does not melt, and at which internal stress occurs that separates the cut portion 14 from the workpiece 11, before the workpiece 11 is heated to recrystallize or melt, and generates the laser beam 21 at the set output.

[0034] Therefore, the present invention can cut the workpiece heated by the laser beam without melting or vaporizing it, minimizing damage.

[0035] To this end, the laser generating unit 20 generates a laser beam 21 having a wavelength and intensity corresponding to the signal from the control unit 70, and the beam generating optical unit 30 converges the laser beam 21 generated by the laser generating unit 20 and irradiates the laser beam 21 at a focal position corresponding to the cutting depth according to the control signal.

[0036] Here, the laser beam 21 is formed in a straight line having a length equal to or slightly longer than the diameter of the ingot. However, the present invention is not limited to this, and the laser beam 21 can be changed to various shapes, such as a shape having a fixed area or a fixed thickness, according to a control signal from the control unit. However, if the length of the laser beam 21 is smaller than the diameter of the ingot, the laser beam 21 can be moved back and forth multiple times to cut the ingot.

[0037] That is, the surface of the object 11 is heated by the transmitted laser beam 21, but the inside of the object 11, particularly the cut surface 12 corresponding to the focus of the laser beam 21, is heated to a higher temperature than the surface of the object 11. Here, an internal stress is generated at the cut surface 12, which separates the cut portion 14 from the object 11.

[0038] The beam generating optical unit 30 further includes a moving unit (not shown) that moves the lens unit along the cutting direction. The moving unit moves the lens unit or adjusts its angle to move the laser beam 21 in response to a control signal from the control unit 70.

[0039] For example, the moving unit may include a driving motor that generates driving force in response to a control signal from the control unit 70, and a moving body that moves by receiving the driving force of the driving motor through a power transmission unit that is configured in various ways, such as a gear, pulley, belt, or chain.

[0040] Meanwhile, minute damage can be generated at a cutting start point 13 on the outer periphery of a cutting surface 12 to be cut in the workpiece 11 so that a cutting portion 14 can be easily cut.

[0041] For this reason, in this embodiment, a start point generating unit 50 that generates minute damage is further provided at the cutting start point 13.

[0042] For example, the starting point generating unit 50 can use a diamond wheel (not shown) to generate initial damage, or can irradiate the cutting starting point 13 with a laser beam emitted from a separate laser generator (not shown) to generate fine damage.

[0043] Such a starting point generating unit 50 can generate damage of a predetermined size by rotating a diamond wheel or driving a laser generator using a driving module (not shown) driven by a control signal from the control unit 70 to irradiate a laser beam onto the cutting starting point 13.

[0044] The separating unit 60 functions to move the cutting portion 14 to be cut from the workpiece 11 upward to easily separate it.

[0045] For example, FIGS. 3 and 4 are diagrams each showing the configuration of a separation unit.

[0046] As shown in Figure 3, the separation part 60 is formed in an approximately ring shape, is fixed to the outer periphery of the cutting area 14, and can be provided as an outer periphery support member that moves the cutting area upward and separates it from the workpiece 11 by the tensile force provided by a tensioning means (not shown).

[0047] Furthermore, as shown in FIG. 4, the separation portion 60 can be formed in an approximately circular or cylindrical shape, and can be provided as an upper contact support member that adheres to the top of the cutting portion 14, and adheres to the cutting portion 14 using an adhesive or the like, allowing the laser beam 21 to pass through the cutting portion 14, and separating the cutting portion 14 from the workpiece 11 by the tensile force.

[0048] Here, it is desirable that the upper contact support member and the adhesive are each made of a light-transmitting material that can transmit all or most of the laser beam 21 to the workpiece 11 side without reflecting or scattering the laser beam 21.

[0049] The separating unit 60 may also be provided as a tension applying member including an upper jig (not shown) and a lower jig (not shown) that apply tension to the lower end and cutting portion of the workpiece 11.

[0050] The cooling section 40 includes a spray nozzle (not shown) that sprays a coolant onto the surface of the workpiece 11, and a regulator (not shown) that adjusts the cooling rate according to the amount and speed of the coolant sprayed through the spray nozzle.

[0051] The injection nozzle can mix a coolant with a fluid to cool the workpiece 11 through the surface irradiated with the laser beam 21 to the inside, and inject the coolant mixed with the fluid at a predetermined pressure.

[0052] For example, the coolant may be a mixture of water and air, which is sprayed at a predetermined pressure toward the irradiation area where the laser beam 21 is irradiated.

[0053] The cooling area where the coolant is injected then allows the laser beam 21 to penetrate to the cutting depth.

[0054] For example, each of FIGS. 5 to 7 shows the layout structure of the cooling unit and the laser generating unit.

[0055] As shown in FIG. 5, the cooling unit 40 is disposed behind the laser generating unit 20 with respect to the cutting direction, that is, on the left side in FIG.

[0056] Therefore, immediately after the laser generating unit 20 irradiates the workpiece 11 with the laser beam 21, the cooling unit 40 supplies a coolant to the cut location 14 of the heated workpiece 11 to cool it.

[0057] As shown in FIG. 6, the cooling section 40 can be configured to supply a coolant to a cooling area formed wider than the irradiation area in the laser generating section 20 so as to include the irradiation area where the laser beam 21 is irradiated.

[0058] Therefore, after the laser beam 21 is irradiated from the laser generating unit 20 toward the workpiece 11, the cooling unit 40 can supply a coolant to the cutting portion 14 of the heated workpiece 11 to cool it.

[0059] On the other hand, in this embodiment, a coolant removal section 41 is further included to solve the problem that the coolant sprayed from the cooling section 40 interferes with the laser beam 21 when heated or vaporized due to heat exchange with the cutting point 14.

[0060] For example, as shown in FIG. 7, the coolant removal unit 41 may include a fan (not shown) arranged in front of the laser generating unit 20 in the cutting direction, i.e., on the right side as viewed in FIG. 7, and may blow out and remove the coolant heated by heat exchange with the cutting point 14 or the vaporized coolant.

[0061] In this way, the cooling region can be formed so as to cool the entire irradiation region irradiated with the laser beam 21 or to cool a part of the irradiation region.

[0062] Therefore, the depth to which the laser beam 21 is absorbed inside the workpiece 11 can vary depending on the cutting depth of the workpiece 11 .

[0063] As described above, the present invention allows a workpiece having thermally brittle properties to be cut to a desired thickness in a slicing manner.

[0064] Next, with reference to FIG. 8, a cutting method using a laser according to a preferred embodiment of the present invention will be described in detail.

[0065] FIG. 8 is a flow chart illustrating the steps of a laser cutting method according to a preferred embodiment of the present invention.

[0066] 8, laser generating unit 20 generates laser beam 21 that passes through the surface of workpiece 11 and is only partially absorbed. Here, in workpiece 11, minute damage has been generated by start point generating unit 50 at cut start point 13 on the outer periphery of cut surface 12 to be cut.

[0067] In step S12, the beam generating optical unit 30 uses a lens unit to focus the laser beam 21 into a shape that extends parallel to the surface of the workpiece 11 and perpendicular to the cutting direction at the cutting depth to be cut from the surface of the workpiece 11, and generates and irradiates a laser beam that heats the workpiece 11 to a temperature below its melting point that does not melt the cut surface 13 of the workpiece 11 but generates internal stress that separates the cut location 14 from the workpiece 11.

[0068] As a result, the object 11 can be cut in a state where the inside is heated by the irradiated laser beam 21 but the cutting surface 13 is not melted.

[0069] In step S14, the cooling unit 40 cools the surface of the work-piece 11 heated by the laser beam 21.

[0070] Here, the cooling section 40 can supply a coolant to the cutting point 14 of the workpiece 11 that has been heated immediately after the laser generating section 20 irradiates the laser beam 21 toward the workpiece 11, thereby cooling it.

[0071] Alternatively, the cooling section 40 can also supply a coolant to the whole or part of the cutting point 14 of the workpiece 11 that has been heated after the laser generating section 20 irradiates the workpiece 11 with a laser beam 21 to cool the workpiece 11.

[0072] In addition, the coolant removal unit 41 drives a fan to blow out and remove the coolant that has been heated by heat exchange with the cutting point 14 or the vaporized coolant, thereby preventing interference between the coolant and the laser beam 21.

[0073] In this way, while the laser beam 21 is irradiated to heat, cool, and cut the workpiece 11, the control unit 70 controls in real time the diameter and cutting depth of the workpiece 110, the intensity of the laser beam 21 irradiated from the laser generating unit 20, the cutting speed at which the laser beam 21 is moved along the cutting direction to cut the workpiece 11, and the cooling speed determined by the amount and speed of the coolant sprayed by the cooling unit 40 (S16).

[0074] In step S18, the separating unit 60 uses the tensile force provided by the pulling means to move the cut portion 14 cut in the workpiece 11 upward and separate it.

[0075] According to the above process, the present invention can slice a workpiece having thermally brittle properties to a desired thickness.

[0076] Furthermore, the present invention can cut an object to be processed with minimal damage by irradiating the object with a laser beam to heat and cool it without melting or vaporizing the object.

[0077] Furthermore, the present invention can easily separate the cut portion of the object using the separating portion, thereby improving the flatness of the cut surface.

[0078] As a result, the present invention can maximize productivity by improving the workability of the cutting operation on the workpiece and eliminating or minimizing post-processing of the cut portion, such as a polishing process performed during wafer manufacturing.

[0079] The invention made by the inventor has been specifically described above using embodiments, but it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways without departing from the spirit of the invention. [Industrial Applicability]

[0080] The present invention is applicable to the technology of a laser-based cutting device and method for cutting a workpiece having thermal brittleness into a desired thickness by slicing. [Explanation of symbols]

[0081] 10 Cutting device 11 Processing object 12 Cut surface 13 Cutting start point 14 Cutting point 20 Laser generating unit 21 Laser beam 30 Beam generating optics 40 Cooling section 41 Coolant removal section 50 Starting point generator 60 Separation part 70 Control Unit

Claims

1. a laser generating unit (20) that generates a laser beam that is transmitted through the surface of the workpiece (11) and only partially absorbed; a beam generating optical unit (30) that focuses the laser beam into a shape that is parallel to the surface of the object (11) and extends perpendicular to the cutting direction at a depth to be cut in the surface of the object (11), and generates a laser beam that heats the cut surface (12) of the object (11) to a temperature that is below the melting point at which the cut surface (12) of the object (11) does not melt and that generates internal stress that separates the cut portion in the object (11); a start point generating unit (50) for generating damage at a cutting start point (13) on the outer periphery of a cutting surface (12) to be cut in an object (11); a separation unit (60) that separates the cut portion of the object (11), The separating portion (60) is an outer shell supporting member fixed to the outer shell of the cutting portion and separating the cutting portion from the workpiece (11) by a tensile force provided by a tensioning means; An upper contact support member that is in close contact with the upper part of the cutting portion, transmits the laser beam through the cutting portion, and separates the cutting portion from the workpiece (11) by a tensile force; and It is provided as one of the tension force applying units that applies tension force to the lower end of the workpiece (11) and the cutting location, Cut the workpiece to the desired thickness in a slice-like manner without melting it and reducing damage. A laser cutting device characterized in that the separation section (60) is used to move the cut portion of the workpiece (11) upward and separate it.

2. The laser cutting device according to claim 1, further comprising a cooling unit (40) that supplies a coolant to a cutting location of the workpiece (11) that has been heated immediately after the laser generating unit (20) irradiates the workpiece (11) with a laser beam, thereby cooling the heated cutting location.

3. Furthermore, a cooling unit (40) supplies a coolant to a cutting portion of the workpiece (11) that has been heated after the laser beam is irradiated from the laser generating unit (20) toward the workpiece (11) to cool it; 2. The laser cutting device according to claim 1, further comprising a coolant removal section (41) for removing the coolant so as to prevent interference between the laser beam and the coolant heated or vaporized by heat exchange with the cutting portion.

4. a control unit (70) that controls the operation of the laser generating unit (20), the beam generating optical unit (30), and the cooling unit (40); 4. The laser cutting device according to claim 2 or 3, wherein the control unit (70) generates a control signal for controlling the diameter and cutting depth of the workpiece (11), the intensity of the laser beam irradiated from the laser generating unit (20), the cutting speed at which the laser beam is moved along the cutting direction to cut the workpiece (11), and the cooling speed based on the amount and speed of coolant sprayed by the cooling unit (40).

5. (a) generating a laser beam in a laser generating unit (20) that passes through the surface of the workpiece (11) and is only partially absorbed; (b) generating damage at a cutting start point (13) of the outer contour of the cutting surface to be cut in the object (11) using a start point generating unit (50); (c) in the beam generating optical unit (30), the laser beam is focused in a shape extending parallel to the surface of the object (11) and perpendicular to the cutting direction at a depth to be cut in the surface of the object (11), and a laser beam is generated and irradiated that heats the cut surface (12) of the object (11) to a temperature below the melting point at which the cut surface (12) is not melted and that generates internal stress that separates the cut portion from the object (11); (d) separating the cut portion of the object (11) using a separating unit (60); Cutting the workpiece (11) to a desired thickness in a slicing manner without melting it and reducing damage; an outer shell support member fixed to the outer shell of the cutting portion and separating the cutting portion from the workpiece (11) by a tensile force provided by a tension means; an upper contact support member that is in close contact with the upper portion of the cutting portion, transmits the laser beam through the cutting portion, and separates the cutting portion from the workpiece (11) by a tensile force; and A cutting method using a laser, characterized in that the cutting point cut in the workpiece (11) is moved upward and separated using the separation unit (60) provided as one of the tensile force providing units that provide tensile force to the lower end of the workpiece (11) and the cutting point.

6. The step (c) includes using a cooling unit (40) to cool the surface of the workpiece (11) heated by the laser beam; 6. The laser cutting method according to claim 5, wherein the cooling unit (40) supplies a coolant to the cutting point of the heated workpiece (11) to cool it immediately after the laser generating unit (20) irradiates the workpiece (11) with a laser beam.

7. The step (c) includes using a cooling unit (40) to cool the surface of the workpiece (11) heated by the laser beam; a coolant removal unit (41) is used to remove the coolant that has been heated or vaporized by heat exchange with the cutting portion so as to prevent interference between the coolant and the laser beam; 6. The laser cutting method according to claim 5, wherein the cooling unit (40) supplies a coolant to a cutting point of the heated workpiece (11) to cool it after the laser beam is irradiated from the laser generating unit (20) toward the workpiece (11).

8. 8. The laser cutting method according to claim 6 or 7, wherein step (c) uses a control unit (70) to control the diameter and cutting depth of the workpiece (11), the intensity of the laser beam irradiated from the laser generating unit (20), the cutting speed at which the laser beam is moved along the cutting direction to cut the workpiece (11), and the cooling speed determined by the amount and speed of coolant sprayed by the cooling unit (40).

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