Laser processing equipment

Abstract

To provide a laser processing device capable of suppressing an error of an inspection result of an SiC ingot.SOLUTION: A laser processing device 1 incudes a chuck table 10 for holding an SiC ingot on a holding surface 11, a laser beam irradiation unit 20 for positioning a condensing point of a laser beam to a depth corresponding to thickness of a wafer to be generated from a first surface, irradiating the SiC ingot with a laser beam, separating the SiC into Si and C, and forming a peeling layer having an extended clack along a c surface, a moving unit 30 for relatively moving the chuck table 10 and the laser beam irradiation unit 20, and a peeling layer inspection unit 40 for emitting inspection light 41 of a wavelength having transmittance to the SiC ingot and reflecting on the peeling layer, and inspecting the peeling layer from intensity of the reflected light. The holding surface 11 has a color for absorbing the inspection light 41.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a laser processing apparatus, and more particularly to a chuck table. [Background technology]

[0002] Devices such as ICs, LSIs, LEDs, and power devices are made of silicon (Si) and aluminum. 2 O 3 Functional layers are laminated on the surface of wafers made of materials such as sapphire and single crystal SiC (silicon carbide), and are then partitioned along the planned division lines. The wafers on which devices are formed are then cut along the planned division lines using cutting equipment and laser processing equipment, and divided into individual devices. Each divided device is used in electrical equipment such as mobile phones and personal computers.

[0003] Wafers on which devices are formed are generally produced by thinly slicing cylindrical ingots with a wire saw. The front and back surfaces of the sliced ​​wafers are polished to a mirror finish. However, when an ingot is sliced ​​with a wire saw and the front and back surfaces of the sliced ​​wafers are polished, most of the ingot (70-80%) is discarded, which is uneconomical. In particular, SiC ingots are hard and difficult to slice with a wire saw, which takes a considerable amount of time, resulting in poor productivity, and the high unit price of the ingot makes it difficult to efficiently produce wafers.

[0004] Therefore, the applicant has proposed a technology in which the focal point of a laser beam having a wavelength that is transparent to single crystal SiC is positioned inside a SiC ingot, the laser beam is irradiated onto the SiC ingot to form a delamination layer on the planned cutting surface, and a wafer is peeled off from the SiC ingot along the planned cutting surface on which the delamination layer has been formed (see, for example, Patent Document 1).

[0005] However, when the height of the SiC ingot is reduced by repeatedly peeling off the wafer and the crystal structure of the intended cutting surface changes, it becomes difficult to form an appropriate peeled off layer along the intended cutting surface under the initial processing conditions. Therefore, a method has been devised in which an inspection light is irradiated onto the peeled off layer during or after laser processing, and whether or not the peeled off layer has been properly formed is confirmed based on the brightness of the reflected light (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6399913 [Patent Document 2] JP 2020-205312 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the wafer production method shown in Patent Document 2 had a problem in that, particularly when the SiC ingot was thin, the brightness of the captured image increased due to the effect of the inspection light reflected by the chuck table (its holding surface), changing the inspection results of the peeling layer, which may lead to erroneous inspection results for each peeling layer.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a laser processing device that can suppress errors in the inspection results of SiC ingots. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, the laser processing apparatus of the present invention is a laser processing apparatus for forming a peeling layer in a SiC ingot, comprising: a chuck table for holding the SiC ingot with a holding surface; a laser beam application unit including a collector for positioning a focal point of a laser beam having a wavelength transparent to SiC at a depth from the top surface of the SiC ingot corresponding to the thickness of a wafer to be produced and irradiating the SiC ingot with the laser beam, thereby separating the SiC into Si and C and forming a peeling layer in which a crack extends along the c-plane; a moving unit for relatively moving the chuck table and the laser beam application unit; and a peeling layer inspection unit for applying inspection light having a wavelength transparent to the SiC ingot and reflected by the peeling layer and inspecting the peeling layer from the intensity of the reflected light. A control unit; having The peeling layer inspection unit irradiates a plurality of peeling layers for inspection formed on the SiC ingot with inspection light by using a laser beam having a different output, and images the plurality of peeling layers for inspection. The control unit sets the output of the laser beam that forms a peeling layer for peeling the wafer from the SiC ingot based on the image captured by the peeling layer inspection unit, and The holding surface of the chuck table absorbs the inspection light. dark It is characterized by its color.

[0010] In the laser processing apparatus, the inspection light may be visible light.

[0011] In the laser processing apparatus, the holding surface of the chuck table may be formed of a porous plate.

[0012] In the laser processing apparatus, the porous plate may be made of porous glass. Effect of the Invention

[0013] The present invention has an effect of suppressing errors in the inspection results of SiC ingots. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a laser processing apparatus according to the first embodiment. [Diagram 2] FIG. 2 is a plan view of a SiC ingot to be processed by the laser processing apparatus shown in FIG. [Diagram 3]FIG. 3 is a side view of the SiC ingot shown in FIG. [Figure 4] FIG. 4 is a perspective view of a wafer produced by peeling off a portion of the SiC ingot shown in FIG. [Diagram 5] 5 is a side view, partially in cross section, of the chuck table of the laser processing apparatus shown in FIG. [Figure 6] FIG. 6 is a perspective view showing a state in which the laser processing apparatus shown in FIG. 1 forms a peeling layer on a SiC ingot. [Figure 7] FIG. 7 is a cross-sectional view showing a part of the state in which the laser processing apparatus shown in FIG. 1 forms a peeling layer on a SiC ingot. [Figure 8] FIG. 8 is a perspective view showing a state in which the laser processing apparatus shown in FIG. 1 forms a peeled layer for inspection on the SiC ingot held on the chuck table. [Figure 9] FIG. 9 is a cross-sectional view showing a part of a state in which the laser processing apparatus shown in FIG. 1 forms a peeled layer for inspection on the SiC ingot held on the chuck table. [Figure 10] FIG. 10 is a side view that illustrates a state in which the peeling layer inspection unit of the laser processing apparatus illustrated in FIG. 1 images an inspection peeling layer formed on a SiC ingot. [Figure 11] FIG. 11 is a diagram showing a schematic view of an image captured and acquired by the peeling layer inspection unit shown in FIG. [Figure 12] FIG. 12 is a side view that illustrates a state in which the detection unit of the laser processing apparatus according to the second embodiment detects the Facet region of the SiC ingot. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 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.

[0016] [Embodiment 1] A laser processing apparatus 1 according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration example of the laser processing apparatus according to the first embodiment. FIG. 2 is a plan view of a SiC ingot to be processed by the laser processing apparatus shown in FIG. 1. FIG. 3 is a side view of the SiC ingot shown in FIG. 2. FIG. 4 is a perspective view of a wafer produced by peeling off a part of the SiC ingot shown in FIG. 2. FIG. 5 is a side view showing a partial cross section of a chuck table of the laser processing apparatus shown in FIG. 1. FIG. 6 is a perspective view showing a state in which the laser processing apparatus shown in FIG. 1 forms a peeling layer on the SiC ingot. FIG. 7 is a cross-sectional view showing a part of a state in which the laser processing apparatus shown in FIG. 1 forms a peeling layer on the SiC ingot.

[0017] (SiC ingot) The laser processing apparatus 1 shown in Fig. 1 according to the first embodiment is a processing apparatus that laser processes a SiC ingot 200 shown in Fig. 2. The SiC ingot 200 shown in Fig. 2 and Fig. 3, which is an object to be processed by the laser processing apparatus 1 according to the first embodiment, is made of SiC (silicon carbide) in the first embodiment and is formed into a cylindrical shape as a whole. In the first embodiment, the SiC ingot 200 is a hexagonal single crystal SiC ingot.

[0018] 2 and 3, the SiC ingot 200 has a first surface 201 which is a circular upper surface, a second surface 202 which is a circular surface on the back side of the first surface 201, and a peripheral surface 203 which is continuous with the outer edge of the first surface 201 and the outer edge of the second surface 202. The SiC ingot 200 also has a first orientation flat 204 which indicates a crystal orientation on the peripheral surface 203, and a second orientation flat 205 which is perpendicular to the first orientation flat 204. A length 204-1 of the first orientation flat 204 is longer than a length 205-1 of the second orientation flat 205.

[0019] The SiC ingot 200 also has a C-axis 208 inclined at an off angle α in an inclination direction 207 toward the second orientation flat 205 with respect to a perpendicular line 206 of the first surface 201, and a c-plane 209 perpendicular to the C-axis 208. The c-plane 209 is inclined at an off angle α with respect to the first surface 201 of the SiC ingot 200. The inclination direction 207 of the C-axis 208 from the perpendicular line 206 is perpendicular to the extension direction of the second orientation flat 205 and is parallel to the first orientation flat 204.

[0020] An infinite number of c-planes 209 are set in the SiC ingot 200 at the molecular level of the SiC ingot 200. In the first embodiment, the off-angle α is set to 1°, 4°, or 6°, but in the present invention, the SiC ingot 200 can be manufactured by freely setting the off-angle α within a range of, for example, 1° to 6°.

[0021] Moreover, the first surface 201 of the SiC ingot 200 is ground by a grinding device, and then polished by a polishing device to form the first surface 201 into a mirror surface. A portion of the SiC ingot 200 on the side of the first surface 201 is peeled off, and the peeled portion is generated into the wafer 220 shown in Fig. 4. Moreover, there are a plurality of types of SiC ingots 200 having different diameters 210.

[0022] The wafer 220 shown in FIG. 4 is manufactured by peeling a portion including the first surface 201 of the SiC ingot 200 as the wafer 220, and performing grinding, polishing, or the like on the peeled surface 221 peeled from the SiC ingot 200. After the wafer 220 is peeled from the SiC ingot 200, a device is formed on the surface. In the first embodiment, the device is a MOSFET (Metal-oxide-semiconductor Field-effect Transistor), a MEMS (Micro Electro Mechanical Systems), or an SBD (Schottky Barrier Diode), but in the present invention, the device is not limited to a MOSFET, a MEMS, or an SBD. Note that the same parts of the wafer 220 as those of the SiC ingot 200 are denoted by the same reference numerals, and description thereof will be omitted.

[0023] 2 and 3, a part of the SiC ingot 200, i.e., the wafer 220 to be produced, is separated and peeled from the peeled layer 211 as a starting point after the peeled layer 211 is formed as shown in FIG. 3. The peeled layer 211 is formed by the laser processing apparatus 1 according to the first embodiment. In addition, the peeled surface 212 of the SiC ingot 200 from which the wafer 220 has been peeled is formed into a mirror surface by grinding and polishing, and the peeled surface 212 is formed on the first surface 201, and the peeled layer 211 is formed again to peel the wafer 220. In this way, the thickness of the SiC ingot 200 becomes thinner as the wafer 220 is peeled off, and the peeled layer 211 is formed until the wafer 220 reaches a predetermined thickness, and the wafer 220 is peeled off.

[0024] (Laser processing equipment) The laser processing apparatus 1 according to the first embodiment is a processing apparatus that forms a peeling layer 211 on a SiC ingot 200. As shown in Fig. 1, the laser processing apparatus 1 has a chuck table 10 that holds the SiC ingot 200, a laser beam application unit 20, a moving unit 30, a peeling layer inspection unit 40 that irradiates the SiC ingot 200 held on the chuck table 10 with inspection light 41 (shown in Fig. 1, visible light in the first embodiment) to inspect the peeling layer 211, and a control unit 100.

[0025] The chuck table 10 is installed on the rotary moving unit 33 of the moving unit 30, and holds the SiC ingot 200 on a holding surface 11 that is parallel to the horizontal direction. As shown in Figures 1 and 5, the chuck table 10 includes a disk-shaped porous plate 12 that constitutes the holding surface 11 that suction-holds the SiC ingot 200, and a base 13 that surrounds the outer periphery of the porous plate 12.

[0026] In the first embodiment, the base 13 is made of a metal such as stainless steel, is a non-porous body having no air permeability, and is formed in a thick disk shape. The base 13 is installed on the rotary moving unit 33 of the moving unit 30. As shown in FIG. 4, the base 13 is formed to have an outer diameter larger than the SiC ingot 200, and a recess 132 in which the porous plate 12 is attached is provided in the center of the upper surface 131. When the porous plate 12 is attached in the recess 132, the upper surface 131 of the base 13 is located on the same plane as the holding surface 11.

[0027] The recess 132 has a circular planar shape, an outer diameter larger than that of the SiC ingot 200, and is disposed at a position coaxial with the base 13. The recess 132 is provided with a plurality of concentric suction grooves 133 on the bottom surface 34 and connecting suction grooves 134 that communicate between the suction grooves 133. These suction grooves 133, 134 are recessed from the bottom surface of the recess 132. In addition, these suction grooves 133, 134 communicate with a communication passage 135 that opens into the bottom surface of the recess 132.

[0028] The communication passage 135 is connected to a suction passage 137 that is connected to a suction source 14 such as an ejector and is provided with an on-off valve 136. When the on-off valve 136 is opened and negative pressure from the suction source 14 acts on the suction passage 137, the base 13 applies negative pressure from the suction source 14 to the porous plate 12 fitted in the recess 132, and sucks the holding surface 11 of the porous plate 12. When the base 13 is placed on the rotational movement unit 33, a branched suction passage 139 that branches off from the suction passage 137 and is provided with an on-off valve 138 faces the bottom surface of the base 13. When the on-off valve 138 is opened and negative pressure from the suction source 14 acts on the branched suction passage 139, the bottom surface of the base 13 is sucked to the rotational movement unit 33 and fixed.

[0029] In the first embodiment, the outer surface of the base 13 (particularly the outer surface closer to the outer periphery than the recess 132) is a color 15 (shown by coarse shading in FIG. 1) that absorbs the inspection light 41. The color 15 that absorbs the inspection light 41 is a color that has a higher absorption rate of the inspection light 41 than the white, brown, and silver colors that have conventionally been used for the outer surface of chuck tables. The color 15 that absorbs the inspection light 41 is preferably a so-called dark color that is a dark chromatic color with low brightness that includes an achromatic dark gray or black, is preferably a deep dark color, and is preferably black.

[0030] Thus, the color 15 that absorbs the inspection light 41 includes a dark color, a deep dark color, and black. In the first embodiment, the outer surface of the base 13 (particularly the outer surface on the outer periphery side of the recess 132) is formed in black, which is the color 15 that absorbs the inspection light 41. In the first embodiment, the outer surface of the base 13 (particularly the outer surface on the outer periphery side of the recess 132) is coated with black paint, which is the color 15 that absorbs the inspection light 41. Thus, in the present invention, it is desirable that the outer surface of the base 13 is formed in a dark color, a deep dark color, or black.

[0031] The porous plate 12 is a disk-shaped porous body having air permeability, the outer diameter of which is larger than the outer diameter of the SiC ingot 200 and equal to the inner diameter of the recess 132. The porous plate 12 is fixed inside the recess 132, and its lower surface is fixed to the bottom surface of the recess 132 of the base 13 with an adhesive (not shown). The upper surface of the porous plate 12 is the holding surface 11 that holds the SiC ingot 200 by suction. For this reason, the holding surface 11 of the chuck table 10 is formed by the porous plate 12.

[0032] The porous plate 12 is fixed to a base 13, and the holding surface 11 is ground to be flat and parallel to the horizontal direction. The holding surface 11 of the porous plate 12 is located on the same plane as an upper surface 131 of the base 13. The porous plate 12 is connected to the suction source 14 via a communication passage 135 and a suction passage 137 provided in the base 13. When an opening / closing valve 136 is opened and negative pressure from the suction source 14 acts on the porous plate 12, the SiC ingot 200 is sucked and held on the holding surface 11.

[0033] In the first embodiment, the porous plate 12 is formed by connecting a plurality of glass particles made of soda glass (soda-lime glass in the first embodiment), which is a glass material that is transparent to visible light. Each glass particle is spherical and has a roughly uniform particle size. The glass particles are preferably dense particles that do not contain air bubbles. Such glass particles can be manufactured, for example, by spray drying.

[0034] A spray dryer (spray drying device) has a nozzle or disk for atomizing the raw glass liquid. The raw glass liquid, which has been atomized into spherical particles by surface tension or the like, is exposed to hot air supplied to a drying chamber, where the atomized raw glass liquid solidifies into spherical glass particles with a uniform particle size.

[0035] In the first embodiment, glass particles having a particle size of 3 μm to 4 mm are used. The particle size of the glass particles is more preferably 5 μm to 300 μm, and further preferably 30 μm to 200 μm.

[0036] The particle size of the glass particles varies according to a Gaussian distribution, but for example, when the particle size of the glass particles is a predetermined value of 100 μm or less, a particle group with a standard deviation of 5 μm or less is used. Also, for example, when the particle size of the glass particles is a predetermined value of 101 μm to 300 μm, a particle group with a standard deviation of 10 μm or less is used.

[0037] The porous plate 12 is manufactured by first placing a plurality of glass particles in a mold (not shown) having a disk-shaped recess and sealing it with a cover plate (not shown).The mold, cover plate, and glass particles are then placed in a firing furnace and fired at a predetermined temperature of 600°C to 1300°C.

[0038] In the first embodiment, the glass particles are fired at a predetermined temperature of 700° C. to 800° C. for a predetermined time of about 30 minutes to about 3 hours. The firing produces a porous plate 12 in which adjacent spherical glass particles are partially connected while leaving pores in the gaps between the glass particles. In this way, the porous plate 12 is made of glass pores.

[0039] The longer the firing time of the glass particles, the longer the time for the glass material to become fluid, so the contact area between the glass particles increases and the porosity decreases. For example, the porosity of the porous plate 12 fired for 3 hours is lower than that of the porous plate 12 fired for 30 minutes.

[0040] In the first embodiment, the porosity of the porous plate 12 is 5% to 40% by volume. The porosity can be appropriately adjusted by the firing temperature, pressure, amount of frit added to the glass particles, etc., in addition to the firing time. The frit is a powder made of the same glass material as the glass particles, but with a smaller diameter than the glass particles.

[0041] When the porous plate 12 is attached to the recess 132 and the base 13 is fixed to the rotational movement unit 33, and the suction pressure of the suction source 14 is -92.7 kPa (gauge pressure), if nothing is placed on the holding surface 11, the pressure in the suction path 137 will be -65 kPa (gauge pressure) or more and -50 kPa (gauge pressure) or less. In addition, when the porous plate 12 is attached to the recess 132 and the base 13 is fixed to the rotational movement unit 33, and the suction pressure of the suction source 14 is -92.7 kPa (gauge pressure), when a SiC ingot 200 having a diameter 210 of 4 inches is placed on the holding surface 11, the pressure in the suction path 137 becomes -84.2 kPa (gauge pressure), when a SiC ingot 200 having a diameter 210 of 6 inches is placed on the holding surface 11, the pressure in the suction path 137 becomes -87.9 kPa (gauge pressure), and when a SiC ingot 200 having a diameter 210 of 8 inches is placed on the holding surface 11, the pressure in the suction path 137 becomes -91.5 kPa (gauge pressure).

[0042] Moreover, in the first embodiment, at least the holding surface 11 of the porous plate 12, like the base 13, is color 15 (shown by dense shading in FIG. 1) that absorbs the inspection light 41. In the first embodiment, the porous plate 12 is formed in black, which is color 15 that absorbs the inspection light 41, by mixing black pigment such as carbon powder or mineral powder into glass particles or the like. Furthermore, in the present invention, like the base 13, at least the holding surface 11 of the porous plate 12 may be coated with black paint, which is color 15 that absorbs the inspection light 41.

[0043] In the first embodiment, the color 15 that absorbs the inspection light 41 is black, but in the present invention, the color is not limited to black as long as the color has a higher absorption rate of the inspection light 41 than the white, brown, and silver colors that have been conventionally used for the outer surface of the chuck table. Thus, in the present invention, it is desirable that the holding surface 11 of the chuck table 10 is formed in a dark color, a deep dark color, or black. In the present invention, the color 15 of the base 13 and the color 15 of the porous plate 12 may be the same color or different colors.

[0044] In embodiment 1, the porous plate 12 is a porous body formed by connecting a number of glass particles to each other, but in the present invention, the porous plate may be a porous body such as a porous ceramic having aggregate, for example abrasive grains such as alumina, and a bond that fixes the aggregate together, with pores formed in the gaps between the aggregate and the bond.

[0045] The chuck table 10 having the above-described configuration is fixed to the rotary transfer unit 33 by being sucked by the suction source 14, and suction-holds the SiC ingot 200 placed on the holding surface 11. In the first embodiment, the chuck table 10 suction-holds the second surface 202 of the SiC ingot 200 on the holding surface 11.

[0046] Furthermore, the chuck table 10 is rotated by the rotary movement unit 33 of the moving unit 30 about an axis parallel to the Z-axis direction which is perpendicular to the holding surface 11 and parallel to the vertical direction. The chuck table 10, together with the rotary movement unit 33, is moved in the X-axis direction parallel to the horizontal direction by the X-axis movement unit 31 of the moving unit 30, and is moved in the Y-axis direction which is parallel to the horizontal direction and perpendicular to the X-axis direction by the Y-axis movement unit 32. The chuck table 10 is moved by the moving unit 30 between the processing region below the laser beam application unit 20 and a carry-in / out region which is away from below the laser beam application unit 20 and where the wafer 220 is carried in and out.

[0047] The laser beam application unit 20 includes a collector 23 which positions a focal point 22 (shown in FIG. 7) of a pulsed laser beam 21 (shown in FIG. 6 and FIG. 7) having a wavelength that is transparent to the SiC ingot 200 held on the chuck table 10 at a depth 213 corresponding to a thickness 222 (shown in FIG. 4) of a wafer 220 to be produced from the first surface 201 of the SiC ingot 200, and irradiates the laser beam 21 onto the SiC ingot 200, separating the SiC into Si and C and forming a peeled layer 211 in which a crack 215 extends along the c-plane 209.

[0048] When the SiC ingot 200 is irradiated with a pulsed laser beam 21 having a wavelength that is transparent to the SiC ingot 200 while being moved relative to the laser beam 21 along the second orientation flat 205, as shown in Figures 6 and 7, the irradiation of the pulsed laser beam 21 separates the SiC into Si (silicon) and C (carbon), and the next pulsed laser beam 21 irradiated is absorbed by the previously formed C, causing the SiC to separate into Si and C in a chain reaction, forming a modified region 214 inside the SiC ingot 200 along the second orientation flat 205, and a crack 215 extending from the modified region 214 along the c-plane 209 is generated. In this way, when the laser beam application unit 20 irradiates the SiC ingot 200 with a pulsed laser beam 21 having a wavelength that is transparent to the SiC ingot 200, a peeling layer 211 is formed in the SiC ingot 200, the peeling layer 211 including a modified portion 214 and a crack 215 formed from the modified portion 214 along the c-plane 209.

[0049] In the first embodiment, as shown in Fig. 1, the laser beam application unit 20 is supported at the tip of a support 4 supported by an upright wall 3 erected from an apparatus body 2. The laser beam application unit 20 includes an oscillator that oscillates a pulsed laser beam 21 for processing a SiC ingot 200, and a collector 23 that focuses the laser beam 21 oscillated from the oscillator onto the SiC ingot 200 held on the holding surface 11 of the chuck table 10 to form a peeling layer 211.

[0050] The condenser 23 includes a condenser lens (not shown) arranged at a position facing the holding surface 11 of the chuck table 10 in the Z-axis direction. The condenser lens transmits the laser beam 21 oscillated from the oscillator and condenses the laser beam 21 at a condensing point 22. In the first embodiment, the condenser 23 is provided so as to be movable in the Z-axis direction by a condensing point moving unit (not shown).

[0051] The moving unit 30 relatively moves the chuck table 10 and the laser beam application unit 20 around axes parallel to the X-axis direction, the Y-axis direction, and the Z-axis direction. The X-axis direction and the Y-axis direction are parallel to the holding surface 11, i.e., the horizontal direction. The X-axis direction is a so-called processing feed direction in which the chuck table 10 is processed and fed when the laser processing apparatus 1 performs laser processing on the SiC ingot 200. The Y-axis direction is perpendicular to the X-axis direction and is a so-called indexing feed direction in which the chuck table 10 is indexed and fed when the laser processing apparatus 1 performs laser processing on the SiC ingot 200.

[0052] The moving unit 30 includes an X-axis moving unit 31 which is an X-axis moving unit that moves the chuck table 10 in the X-axis direction, a Y-axis moving unit 32 which is a Y-axis moving unit that moves the chuck table 10 in the Y-axis direction, and a rotational moving unit 33 which rotates the chuck table 10 around an axis parallel to the Z-axis direction.

[0053] The Y-axis moving unit 32 is a unit that relatively indexes and feeds the chuck table 10 and the laser beam application unit 20. In the first embodiment, the Y-axis moving unit 32 is installed on the device body 2 of the laser processing device 1. The Y-axis moving unit 32 supports a moving plate 5 that supports the X-axis moving unit 31 so as to be movable in the Y-axis direction.

[0054] The X-axis moving unit 31 is a unit that relatively processes and feeds the chuck table 10 and the laser beam application unit 20. The X-axis moving unit 31 is installed on a moving plate 5. The X-axis moving unit 31 supports a second moving plate 6 that supports a rotation moving unit 33 that rotates the chuck table 10 around an axis parallel to the Z-axis direction, so as to be freely movable in the X-axis direction.

[0055] The X-axis moving unit 31 and the Y-axis moving unit 32 each include a well-known ball screw that is rotatable around its axis, a well-known pulse motor that rotates the ball screw around its axis, and a well-known guide rail that supports the moving plates 5 and 6 so that they can move freely in the X-axis or Y-axis direction.

[0056] The laser processing apparatus 1 also includes an X-axis position detection unit (not shown) for detecting the position of the chuck table 10 in the X-axis direction, a Y-axis position detection unit (not shown) for detecting the position of the chuck table 10 in the Y-axis direction, and a Z-axis position detection unit for detecting the position of the focusing lens included in the laser beam application unit 20 in the Z-axis direction. Each position detection unit outputs a detection result to the control unit 100.

[0057] The delamination layer inspection unit 40 irradiates the SiC ingot 200 held on the chuck table 10 with inspection light 41 having a wavelength that is transparent to the SiC ingot 200 and is reflected by the delamination layer 211, and inspects the delamination layer 211 based on the intensity of the reflected light. The delamination layer inspection unit 40 includes a light emitter 42 that irradiates the inspection light 41 onto the delamination layer 211 formed on the SiC ingot 200 held on the chuck table 10, and a camera 43 that captures an image of the delamination layer 211.

[0058] Inspection light 41 irradiated by light emitting body 42 passes through first surface 201 of SiC ingot 200 and is reflected by cracks 215 in peeling layer 211. Inspection light 41 is also reflected from holding surface 11 of chuck table 10. As the thickness of SiC ingot 200 becomes thinner, the intensity of inspection light 41 reflected from holding surface 11 of chuck table 10 becomes stronger.

[0059] The camera 43 includes an imaging element such as a CCD (Charge Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element that images the inspection light 41 reflected from the peeling layer 211 and the holding surface 11. In the first embodiment, the peeling layer inspection unit 40 is attached to the tip of the support 4 and arranged at a position aligned in the X-axis direction with the focusing lens of the collector 23 of the laser beam application unit 20. The peeling layer inspection unit 40 images the SiC ingot 200, acquires the image, and outputs it to the control unit 100.

[0060] In the first embodiment, the image captured by the peeling layer inspection unit 40 is a grayscale image or a color image in which the intensity of the inspection light 41 is defined by multiple gradations (e.g., 256 gradations). In the first embodiment, the inspection light 41 irradiated onto the SiC ingot 200 by the light emitting body 42 and the inspection light 41 captured by the camera 43 are both visible light.

[0061] The control unit 100 controls each of the above-mentioned components of the laser processing apparatus 1 to cause the laser processing apparatus 1 to perform processing operations on the wafer 220. The control unit 100 is a computer having an arithmetic processing device having a microprocessor such as a CPU (central processing unit), a storage device having a memory such as a ROM (read only memory) or a RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit 100 performs arithmetic processing according to a computer program stored in the storage device, and outputs control signals for controlling the laser processing apparatus 1 to the above-mentioned components of the laser processing apparatus 1 via the input / output interface device, thereby realizing the functions of the control unit 100.

[0062] The control unit 100 is also connected to a display unit 110 configured with a liquid crystal display device or the like that displays the status and images of the machining operation, and an input unit (not shown) that an operator uses to register machining content information, etc. The input unit is configured with at least one of a touch panel provided on the display unit 110 and an external input device such as a keyboard.

[0063] Next, the processing operation of the laser processing apparatus 1 according to the first embodiment will be described. FIG. 8 is a perspective view showing a state in which the laser processing apparatus shown in FIG. 1 forms a peeling layer for inspection on the SiC ingot held on the chuck table. FIG. 9 is a cross-sectional view showing a part of a state in which the laser processing apparatus shown in FIG. 1 forms a peeling layer for inspection on the SiC ingot held on the chuck table. FIG. 10 is a side view diagrammatically showing a state in which a peeling layer inspection unit of the laser processing apparatus shown in FIG. 1 images a peeling layer for inspection formed on the SiC ingot. FIG. 11 is a diagram diagrammatically showing an image captured by the peeling layer inspection unit shown in FIG. 10.

[0064] In the laser processing apparatus 1, the processing conditions are registered in the control unit 100 by an operator, the chuck table 10 is placed on the rotary transfer unit 33, and the second surface 202 of the SiC ingot 200 is placed on the holding surface 11 of the chuck table 10. When the control unit 100 of the laser processing apparatus 1 receives an instruction to start the processing operation from the operator, it opens the on-off valve 138, fixes the chuck table 10 to the rotary transfer unit 33, and starts the processing operation.

[0065] In the processing operation, the control unit 100 of the laser processing apparatus 1 opens the on-off valve 136, and as shown in Fig. 5, the second surface 202 of the SiC ingot 200 is sucked and held on the holding surface 11 of the chuck table 10. In the processing operation, the control unit 100 of the laser processing apparatus 1 controls the moving unit 30 to move the chuck table 10 to below the camera 43 of the peeled layer inspection unit 40, and causes the camera 43 to capture an image of the SiC ingot 200.

[0066] Based on the image of SiC ingot 200 captured by camera 43, control unit 100 of laser processing apparatus 1 adjusts the position of chuck table 10 with X-axis moving unit 31 and Y-axis moving unit 32 to position the outer peripheral region of SiC ingot 200 (outer peripheral excess region in wafer 220 produced from SiC ingot 200 where no device is formed) directly under collector 23 of laser beam application unit 20. In addition, control unit 100 of laser processing apparatus 1 adjusts the orientation of chuck table 10 around its axis with rotational moving unit 33 to make second orientation flat 205 parallel to the X-axis direction, make the direction perpendicular to tilt direction 207 parallel to the X-axis direction, and make tilt direction 207 parallel to the Y-axis direction.

[0067] Next, the control unit 100 of the laser processing apparatus 1 adjusts the position of the collector 23 in the Z-axis direction using the collector moving unit, and positions the collector 22 of the laser beam 21 at a depth 213 corresponding to the thickness 222 of the wafer 220 to be produced from the first surface 201 of the SiC ingot 200. The control unit 100 of the laser processing apparatus 1 irradiates the SiC ingot 200 with the laser beam 21 having a wavelength transparent to SiC from the collector 23 while feeding the chuck table 10 in the X-axis direction, i.e., along the second orientation flat 205, at a predetermined processing feed rate using the X-axis moving unit 31, to form a peeled layer 216 for inspection. In addition, the peeling layer 216 for inspection is formed in the outer peripheral region (outer peripheral excess region where no devices are formed) about 2 mm inside from the outer edge of the SiC ingot 200, so that the peeling layer 216 for inspection does not degrade the quality of the device when a device is formed on the wafer 220 produced from the SiC ingot 200.

[0068] Moreover, when forming the peeling layer 216 for inspection, the control unit 100 of the laser processing apparatus 1 irradiates the SiC ingot 200 with a pulsed laser beam 21 while changing the output of the laser beam 21 irradiated by the laser beam application unit 20, to form a plurality of peeling layers 216 for inspection having different outputs of the laser beam 21. The peeling layer 216 for inspection, like the peeling layer 211, includes a modified portion where SiC is separated into Si (silicon) and C (carbon) by irradiation with the pulsed laser beam 21 and the next irradiated pulsed laser beam 21 is absorbed by the previously formed C, causing the SiC to be separated into Si and C in a chain reaction, and a crack extending from the modified portion along the c-plane 209.

[0069] In the first embodiment, as shown in Fig. 8, the laser processing device 1 forms a peeling layer 216 (hereinafter, indicated by reference numeral 216-1) formed by irradiation with a laser beam 21 of a first output (4 W in the first embodiment), a peeling layer 216 (hereinafter, indicated by reference numeral 216-2) formed by irradiation with a laser beam 21 of a second output (5 W in the first embodiment) different from the first output, a peeling layer 216 (hereinafter, indicated by reference numeral 216-3) formed by irradiation with a laser beam 21 of a third output (6 W in the first embodiment) different from both the first output and the second output, and a peeling layer 216 (hereinafter, indicated by reference numeral 216-4) formed by irradiation with a laser beam 21 of a fourth output (7 W in the first embodiment) different from all of the first output, the second output, and the third output. The output and the number of the peeling layers 216-1, 216-2, 216-3, and 216-4 can be set arbitrarily.

[0070] The control unit 100 of the laser processing apparatus 1 moves the chuck table 10 with the Y-axis moving unit 32, thereby moving the SiC ingot 200 a predetermined distance 24 in the Y-axis direction, i.e., along the first orientation flat 204, relative to the laser beam irradiation unit 20 (hereinafter referred to as index feed). The control unit 100 of the laser processing apparatus 1 alternately repeats the irradiation of the laser beam 21 and index feeding a predetermined number of times while moving the chuck table 10 along the second orientation flat 205 by the X-axis moving unit 31, and forms multiple peeling layers 216-1, 216-2, 216-3, 216-4 having different outputs of the laser beam 21 along the second orientation flat 205 at intervals, as shown in FIG. 9, and also forms multiple peeling layers 216-1, 216-2, 216-3, 216-4 formed by irradiating the laser beam 21 of each output at intervals along the first orientation flat 204.

[0071] 10, the control unit 100 of the laser processing device 1 irradiates the peeling layers 216-1, 216-2, 216-3, and 216-4 with inspection light 41 from the light emitting body 44, captures the peeling layers 216-1, 216-2, 216-3, and 216-4 with the camera 43, and outputs an image 300 (shown in FIG. 11) acquired by the camera 43 to the control unit 100. In the image 300 acquired by the camera 43 shown in FIG. 11, the intensity of the inspection light 41 reflected by the region 301 (shown in white in FIG. 11) where a crack is formed is stronger than the intensity of the inspection light 41 reflected by the region 302 (shown in parallel diagonal lines in FIG. 11) where a crack is not formed and the region 303 (shown in black in FIG. 11) where a modified portion is formed.

[0072] Note that Figure 11(A) is an image 300 (hereinafter, indicated by reference symbol 300-1) acquired by imaging peeling layer 216-1 formed by irradiation with laser beam 21 of a first output, Figure 11(B) is an image 300 (hereinafter, indicated by reference symbol 300-2) acquired by imaging peeling layer 216-2 formed by irradiation with laser beam 21 of a second output, Figure 11(C) is an image 300 (hereinafter, indicated by reference symbol 300-3) acquired by imaging peeling layer 216-3 formed by irradiating laser beam 21 of a third output, and Figure 11(D) is an image 300 (hereinafter, indicated by reference symbol 300-4) acquired by imaging peeling layer 216-4 formed by irradiating laser beam 21 of a fourth output.

[0073] 11(A) and 11(B), in the peeling layers 216-1 and 216-2, adjacent cracks in the inclined direction 207 are spaced apart. In addition, in the peeling layers 216-3 and 216-4, adjacent cracks in the inclined direction 207 overlap each other in FIG.

[0074] Here, in the SiC ingot 200, if the cracks 215 adjacent to each other in the inclination direction 207 do not overlap each other, it is difficult to peel the wafer 220 from the SiC ingot 200 starting from the peeling layer 211. On the other hand, in the SiC ingot 200, if the cracks 215 adjacent to each other in the inclination direction 207 overlap each other, it is possible to easily peel the wafer 220 from the SiC ingot 200 starting from the peeling layer 211. However, if the output of laser beam 21 is excessively high, excessive cracks 215 will occur along c-plane 209 which is inclined relative to first surface 201 of SiC ingot 200, and after wafer 220 is peeled from SiC ingot 200, the amount of grinding required when grinding and flattening peeled surface 212 of SiC ingot 200 and peeled surface 221 of wafer 220 will increase, resulting in increased material loss.

[0075] In the first embodiment, the control unit 100 of the laser processing device 1 extracts images 300-1, 300-2, 300-3, and 300-4 in which all cracks overlap with adjacent cracks in the inclination direction 207, and further extracts an image with the minimum output of the laser beam 21. In the first embodiment, the control unit 100 extracts the image 300-3. The control unit 100 of the laser processing device 1 sets the output of the laser beam 21 of the extracted image 300-3 as the output of the laser beam 21 that forms the peeling layer 211 for peeling the wafer 220 from the SiC ingot 200. In the first embodiment, the control unit 100 sets the third output of the laser beam 21 when the peeling layer 216-3 of the image 300-3 is formed as the output of the laser beam 21 that forms the peeling layer 211 for peeling the wafer 220 from the SiC ingot 200.

[0076] In embodiment 1, control unit 100 sets the output of laser beam 21 for forming peeling layer 211 for peeling wafer 220 from SiC ingot 200 by, for example, extracting from images 300-1, 300-2, 300-3, and 300-4 those in which all cracks overlap with adjacent cracks in inclination direction 207. However, in the present invention, it may be possible to determine whether the output of laser beam 21 when forming each peeling layer 216-1, 216-2, 216-3, and 216-4 is an output that properly forms cracks, depending on whether the brightness of images 300-1, 300-2, 300-3, and 300-4 captured by camera 43 is within a threshold value.

[0077] In this case, when the control unit 100 receives the data of the images 300-1, 300-2, 300-3, and 300-4 from the camera 43, it binarizes each of the images 300-1, 300-2, 300-3, and 300-4 using a predetermined threshold value. Note that the threshold value is preferably smaller than the intensity of the inspection light 41 reflected by the region 301 where a crack is formed, and larger than the intensity of the inspection light 41 reflected by the region 302 where no crack is formed and the region 303 where a modified portion is formed.

[0078] After the binarization process, in each of the images 300-1, 300-2, 300-3, and 300-4, the region 301 where the cracks are formed is mainly white, while the region 302 where the cracks are not formed and the region 303 where the modified portion is formed are mainly black. If the ratio of black to white in the binarized images 300-1, 300-2, 300-3, and 300-4 is within a predetermined value (for example, the ratio of black is 30 to 40% and the ratio of white is 60 to 70%), the control unit 100 determines that the output is such that the cracks are properly formed. The control unit 100 sets the minimum output among the outputs at which the cracks are properly formed as the output of the laser beam 21 that forms the peeling layer 211 for peeling the wafer 220 from the SiC ingot 200.

[0079] In the processing operation, the control unit 100 of the laser processing device 1 sets the output of the laser beam 21, and then controls the moving unit 30 based on the image of the SiC ingot 200 captured by the camera 43 to adjust the relative positions of the SiC ingot 200 and the condenser 23 of the laser beam application unit 20, so that in the first embodiment, the outer edge of the SiC ingot 200 close to the second orientation flat 205 faces the condenser 23 along the Z-axis direction. At this time, the control unit 100 of the laser processing device 1 makes the second orientation flat 205 parallel to the X-axis direction, makes the direction perpendicular to the tilt direction 207 parallel to the X-axis direction, and makes the tilt direction 207 parallel to the Y-axis direction.

[0080] In the processing operation, the control unit 100 of the laser processing apparatus 1 adjusts the position of the collector 23 in the Z-axis direction using the collector moving unit, and positions the collector 22 of the laser beam 21 at a depth 213 corresponding to the thickness 222 of the wafer 220 to be produced from the first surface 201 of the SiC ingot 200. As shown in Fig. 6, the control unit 100 of the laser processing apparatus 1 irradiates the SiC ingot 200 with the laser beam 21 having a wavelength transparent to SiC from the collector 23 while feeding the chuck table 10 at a predetermined processing feed rate using the X-axis moving unit 31.

[0081] As shown in FIG. 7, when a laser beam 21 is irradiated onto a SiC ingot 200, SiC is separated into Si (silicon) and C (carbon), and the next pulse of laser beam 21 irradiated is absorbed by the previously formed C, causing the SiC to separate into Si and C in a chain reaction, forming a modified portion 214, and a crack 215 extending from modified portion 214 along the c-plane 209.

[0082] When the control unit 100 of the laser processing apparatus 1 forms the peeling layer 211 over the entire length in the X-axis direction of the outer edge part of the SiC ingot 200 close to the second orientation flat 205, the Y-axis moving unit 32 indexes the chuck table 10 along the first orientation flat 204 by a predetermined movement distance 24 in the direction in which the condenser 23 of the laser beam application unit 20 moves toward the center of the first surface 201 of the SiC ingot 200. The control unit 100 of the laser processing apparatus 1 alternately repeats the irradiation of the laser beam 21 while moving the chuck table 10 in the X-axis direction by the X-axis moving unit 31 and the indexing until the peeling layer 211 is formed over the entire lower part of the first surface 201, and ends the processing operation.

[0083] As a result, in the SiC ingot 200, a peeled layer 211 having a lower strength than other parts including a modified part 214 where SiC is separated into Si and C and a crack 215 is formed at a depth 213 corresponding to the thickness 222 of the wafer 220 from the first surface 201 for each index feed movement distance 26. In the SiC ingot 200, a peeled layer 211 is formed at a depth 213 corresponding to the thickness 222 of the wafer 220 from the first surface 201 over the entire length in the direction parallel to the first orientation flat 204 for each index feed movement distance.

[0084] As described above, in the laser processing apparatus 1 according to the first embodiment, the holding surface 11 of the chuck table 10 is formed in the color 15 that absorbs the inspection light 41, so that even if the SiC ingot 200 becomes thinner and the peeling layer 211 approaches the holding surface 11, the holding surface 11 has the color 15 that absorbs the inspection light 41, so that the intensity of the inspection light 41 reflected from the holding surface 11 can be suppressed. As a result, the laser processing apparatus 1 can suppress errors in the inspection results of the peeling layers 216-1, 216-2, 216-3, and 216-4 for inspection formed on the SiC ingot 200. In particular, in the laser processing apparatus 1 of embodiment 1, the holding surface 11 of the chuck table 10 is formed in a color 15 that absorbs the inspection light 41, so that near the outer periphery of the SiC ingot 200, the influence of reflected light from the holding surface 11 and the outer surface of the base 13 is large, and therefore errors in the inspection results of the inspection peeling layers 216-1, 216-2, 216-3, and 216-4 can be effectively suppressed.

[0085] In addition, in the laser processing apparatus 1 of embodiment 1, the outer surface of the base 13 of the chuck table 10 is formed in a color 15 that absorbs the inspection light 41, so that the intensity of the inspection light 41 reflected from the outer surface of the base 13 of the chuck table 10 can be suppressed.

[0086] Furthermore, in the laser processing apparatus 1 of embodiment 1, when the porosity of the porous plate 12 is 5% or more and 40% or less in volume ratio and the suction pressure of the suction source 14 is -92.7 kPa (gauge pressure), if nothing is placed on the holding surface 11, the pressure in the suction path 137 is -65 kPa (gauge pressure) or more and -50 kPa (gauge pressure) or less, if a SiC ingot 200 having a diameter 210 of 4 inches is placed on the holding surface 11, the pressure in the suction path 137 is -84.2 kPa (gauge pressure), if a SiC ingot 200 having a diameter 210 of 6 inches is placed on the holding surface 11, the pressure in the suction path 137 is -87.9 kPa (gauge pressure), and if a SiC ingot 200 having a diameter 210 of 8 inches is placed on the holding surface 11, the pressure in the suction path 137 is -91.5 kPa (gauge pressure).

[0087] As a result, the laser processing apparatus 1 can suck and hold the SiC ingots 200 of various sizes on the holding surface 11 without causing any hindrance to the laser processing.

[0088] [Embodiment 2] A laser processing apparatus according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 12 is a side view showing a state in which a detection unit of the laser processing apparatus according to the second embodiment detects a Facet region of a SiC ingot. In Fig. 12, the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted.

[0089] The laser processing apparatus 1 according to the second embodiment further includes a detection unit 50 shown in FIG.

[0090] The SiC ingot 200 may have a region 217 with a different crystal structure called a facet (hereinafter, referred to as a facet region) inside. The facet region 217 has a higher refractive index and a higher energy absorption rate than the non-facet region. For this reason, if the SiC ingot 200 has a facet region 217, the position and completion of the peeled layer 211 formed inside by the irradiation of the laser beam 21 become non-uniform, and there is a problem that a step occurs in the peeled layer 211 and the wafer 220 to be produced between the facet region 217 and the non-facet region.

[0091] The detection unit 50 irradiates the SiC ingot 200 with excitation light 57 of a predetermined wavelength from the first surface 201 of the SiC ingot 200 to detect the brightness of fluorescence 58 inherent to SiC, and detects the positions where the brightness of the fluorescence 58 is detected to be equal to or greater than a predetermined value as non-Facet regions, and detects the regions where the brightness of the fluorescence 58 is lower than the predetermined value as Facet regions 217.

[0092] As shown in FIG. 12, detection unit 50 includes a case 51 supported on the tip of support 4, a light source 52 that emits excitation light 57 of a predetermined wavelength (e.g., 370 nm) at a low output (e.g., 0.1 W) that is not sufficient to perform laser processing on SiC ingot 200, a dichroic mirror 53 that reflects excitation light 57 of the predetermined wavelength emitted from light source 52 and transmits light of wavelengths other than a first predetermined wavelength range (e.g., 365 nm to 375 nm) that includes the above-mentioned predetermined wavelength, a focusing lens 54 that collects excitation light 57 reflected by dichroic mirror 53 and irradiates SiC ingot 200 with the same, a bandpass filter 55 that transmits light in a second predetermined wavelength range (e.g., 395 nm to 430 nm), and a photodetector 56 that detects the brightness of the light that has transmitted through bandpass filter 55.

[0093] In addition, in the detection unit 50, a light source 52, a dichroic mirror 53, a condenser lens 54, and a bandpass filter 55 are arranged in a case 51. In addition, although not shown, the detection unit 50 includes a condenser position adjustment means that adjusts the position of the condenser of the excitation light 57 in the Z-axis direction by raising and lowering the case 51, and this condenser position adjustment means includes, for example, a ball screw that is connected to the case 51 and extends in the Z-axis direction, and a motor that rotates the ball screw.

[0094] The control unit 100 of the laser processing apparatus 1 according to the second embodiment controls the moving unit 30 to relatively move the detection unit 50 and the chuck table 10 while irradiating the first surface 201 of the SiC ingot 200 held on the holding surface 11 of the chuck table 10 with excitation light 57 at predetermined intervals and detecting the fluorescence brightness of the first surface 201 of the SiC ingot 200 at predetermined intervals. At this time, the excitation light 57 oscillated from the light source 52 is reflected by the dichroic mirror 53 and guided to the condenser lens 54, where it is condensed and irradiated onto the first surface 201 of the SiC ingot 200.

[0095] When the SiC ingot 200 is irradiated with the excitation light 57, fluorescence (radiated light) FL containing a wavelength (for example, about 410 nm) different from the wavelength of the excitation light 57 is emitted from the SiC ingot 200. After the fluorescence 58 passes through the condenser lens 54 and the dichroic mirror 53, only the fluorescence 58 in the second predetermined wavelength range passes through the bandpass filter 55, and the luminance of the fluorescence 58 that has passed through the bandpass filter 55 is detected by the photodetector 56. In the laser processing apparatus 1, the detection unit 50 detects the luminance of the fluorescence 58 specific to SiC from the entire first surface 201 of the SiC ingot 200 with the photodetector 56.

[0096] The photodetector 56 outputs a signal indicating that the luminance of the detected fluorescence 58 is equal to or greater than a predetermined value, or a signal indicating that the luminance of the detected fluorescence 58 is lower than the predetermined value, to the control unit 100. Based on the detection results of the X-axis direction position detection unit and the Y-axis direction position detection unit, the control unit 100 detects a position where the luminance of the fluorescence 58 is equal to or greater than a predetermined value as a non-Facet region, and detects a region where the luminance of the fluorescence 58 is lower than the predetermined value as a Facet region 217.

[0097] The laser processing apparatus 1 of embodiment 2 appropriately controls the processing conditions for irradiating the SiC ingot 200 with the laser beam 21 based on the detected positions of the Facet region and non-Facet region, thereby forming a peeling layer 211 without any step between the Facet region 217 and the non-Facet region, thereby suppressing the step in the wafer 220.

[0098] In the laser processing apparatus 1 according to the second embodiment, even if the SiC ingot 200 becomes thinner and the peeling layer 211 approaches the holding surface 11, the holding surface 11 has a color 15 that absorbs the inspection light 41, so that the influence of the fluorescence 58 from the holding surface 11 can be suppressed. As a result, the laser processing apparatus 1 can suppress errors in the detection results of the facet region 217 and the non-facet region of the SiC ingot 200, i.e., the inspection results of the SiC ingot 200.

[0099] In this way, the laser processing apparatus 1 can suppress the fluorescence measured when the holding surface 11 is the above-mentioned color 15, compared to the conventionally used chuck table. As a result, the laser processing apparatus 1 has an effect of reducing the influence of the fluorescence of the chuck table 10 when detecting the presence or absence of the Facet region 217 even if the SiC ingot 200 is thin, and the chuck table 10 having the above-mentioned configuration may be used when irradiating the SiC ingot 200 with the excitation light 57 and detecting the Facet region 217 by detecting the fluorescence 58 of the SiC ingot 200.

[0100] In particular, in the laser processing apparatus 1 of embodiment 2, there is a SiC ingot 200 that has a facet region 217 near the outer periphery of the SiC ingot, and in detecting the facet region 217, inspection is performed up to the very outer periphery of the SiC ingot 200. Therefore, since the holding surface 11 of the chuck table 10 is formed in a color 15 that absorbs the inspection light 41, the influence of reflected light from the holding surface 11 and the outer surface of the base 13 is large near the outer periphery of the SiC ingot 200. Therefore, errors in the detection results of the facet region 217 and non-facet regions of the SiC ingot 200, i.e., the inspection results of the SiC ingot 200, can be effectively suppressed.

[0101] The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the gist of the present invention. For example, in the above embodiment, the base 13 of the chuck table 10 is made of a metal such as stainless steel, but in the present invention, the base 13 is not limited to a metal such as stainless steel, and may be made of various glasses such as soda glass (soda-lime glass), borosilicate glass, or quartz glass, which are glass materials, as long as the material is a non-porous material with no air permeability, or may be made of ceramics. [Explanation of symbols]

[0102] 1 Laser processing equipment 10 Chuck table 11 Holding surface 12 Porous Plate 15 colors 20 Laser beam irradiation unit 21 Laser Beam 22 Focus point 23 Concentrator 30 Mobile Units 40 Peeling layer inspection unit 41 Inspection Light 200 SiC ingot 201 1st side (top side) 211 Peeling layer 213 Depth 220 Wafers 222 Thickness

Claims

1. A laser processing apparatus for forming a peeling layer on a SiC ingot, a chuck table that holds the SiC ingot on a holding surface; a laser beam application unit including a condenser for irradiating the SiC ingot with the laser beam by positioning a focal point of a laser beam having a wavelength that is transparent to SiC at a depth from the top surface of the SiC ingot that corresponds to the thickness of a wafer to be produced, and for separating the SiC into Si and C and forming a peeled layer in which cracks extend along the c-plane; a moving unit for relatively moving the chuck table and the laser beam application unit; a separation layer inspection unit that is transparent to the SiC ingot, irradiates an inspection light having a wavelength that is reflected by the separation layer, and inspects the separation layer based on the intensity of the reflected light; A control unit, The peeling layer inspection unit irradiates a plurality of peeling layers for inspection formed on the SiC ingot with the inspection light by using a laser beam having a different output, and captures images of the plurality of peeling layers for inspection; The control unit sets the output of the laser beam that forms a delamination layer for delaminating the wafer from the SiC ingot based on the image captured by the delamination layer inspection unit, and A laser processing apparatus in which the holding surface of the chuck table is a dark color that absorbs the inspection light.

2. 2. The laser processing apparatus according to claim 1, wherein the inspection light is visible light.

3. 3. The laser processing apparatus according to claim 1, wherein the holding surface of the chuck table is formed of a porous plate.

4. 4. The laser processing apparatus according to claim 3, wherein the porous plate is made of porous glass.

Images