Inspection equipment and laser processing equipment

Abstract

To suppress errors in the inspection results of a facet region of an SiC ingot.SOLUTION: A laser processing device 1 includes a chuck table 10 that holds an SiC ingot on a holding surface 11, and a facet inspection unit including an inspection light irradiation portion that irradiates inspection light onto the SiC ingot held on the chuck table 10, and a light receiving portion 53 that collects and receives fluorescence generated by being excited by the inspection light, and a scattering portion 111 that suppress the fluorescence of the holding surface from being focused on the light receiving portion is formed in a region corresponding to the outer peripheral edge of the SiC ingot on the holding surface 11 of the chuck table 10.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an inspection device and a laser processing device. [Background technology]

[0002] Devices such as ICs, LSIs, LEDs, and power devices are formed by laminating functional layers on the surface of wafers made from materials such as Si (silicon), Al2O3 (sapphire), or single-crystal SiC (silicon carbide), and then dividing the wafer into sections along planned division lines. Wafers with formed devices are then processed along the planned division lines using cutting equipment and laser processing equipment to separate them into individual devices, and each of these devices 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, cutting an ingot with a wire saw and polishing the front and back surfaces of the sliced ​​wafers results in the disposal of most of the ingot (70-80%), which is uneconomical. In particular, SiC ingots are difficult to cut with a wire saw due to their high hardness, which makes cutting them a long process, resulting in poor productivity. In addition, the high unit cost of the ingot poses challenges in efficiently producing wafers.

[0004] Therefore, the present 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 the SiC ingot, the laser beam is irradiated onto the SiC ingot to form a peeling layer on the intended cutting surface, and wafers are peeled off from the SiC ingot along the intended cutting surface on which the peeling layer has been formed (see, for example, Patent Document 1).

[0005] However, SiC ingots may contain regions with different crystal structures, known as facet regions. Compared to non-facet regions, facet regions have a higher refractive index and a higher energy absorption rate. As a result, the position and quality of the delamination layer formed inside the SiC ingot by irradiation with a laser beam become non-uniform, resulting in the problem of steps on the wafer between the facet and non-facet regions.

[0006] For this reason, the applicant of the present invention has proposed a detection device that detects the facet region by irradiating an SiC ingot with excitation light of a predetermined wavelength and detecting the brightness of the fluorescence specific to SiC (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6399913 [Patent Document 2] Japanese Patent Publication No. 2020-077783 Summary of the Invention [Problem to be solved by the invention]

[0008] However, when the SiC ingot becomes thinner due to repeated wafer peeling, there is a risk that the fluorescence from the holding surface of the chuck table may cause erroneous inspection results for the facet area. In particular, the fluorescence from the holding surface of the chuck table becomes stronger near the outer edge of the SiC ingot, and even if a facet area exists near the outer edge of the SiC ingot, it may be detected as a non-facet area.

[0009] The present invention has been made in view of the above facts, and its object is to provide an inspection device and a laser processing device that can suppress errors in the inspection results of the facet region of a SiC ingot. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems and achieve the object, the inspection device of the present invention comprises: It had a circular flat first surface and a circular flat second surface on the reverse side of the first surface. An inspection device for inspecting facet regions of a SiC ingot with different impurity concentrations includes a chuck table that holds the SiC ingot on a holding surface, an inspection light irradiating unit that irradiates the SiC ingot held on the chuck table with inspection light, and a light receiving unit that collects and receives fluorescence excited by the inspection light. overlap The region is characterized by having a scattering portion formed therein that prevents the fluorescence from the holding surface from being collected on the light receiving portion. The inspection device may include a scattering unit corresponding to a SiC ingot of a first diameter and a scattering unit corresponding to a SiC ingot of a second diameter larger than the first diameter.

[0011] In the inspection device, the scattering portion may be an area formed lower than the holding surface of the chuck table, or may be an uneven surface.

[0012] In the inspection apparatus, the holding surface of the chuck table may be made of glass.

[0013] The laser processing apparatus of the present invention is It had a circular flat first surface and a circular flat second surface on the reverse side of the first surface. a laser processing device for forming a peeling layer on a SiC ingot, the device comprising: a chuck table for holding the SiC ingot on a holding surface; a facet area inspection unit including an inspection light irradiator for irradiating inspection light onto the SiC ingot held on the chuck table; and a light receiver for collecting and receiving fluorescence emitted by the inspection light; a laser processing unit for irradiating the SiC ingot held on the chuck table with a laser beam by positioning a focusing point of a laser beam having a wavelength that is transparent to the SiC ingot at a depth from the top surface of the SiC ingot corresponding to the thickness of a wafer to be produced, thereby forming a peeling layer in which cracks have extended; and a moving unit for moving the facet area inspection unit and the laser processing unit relative to the chuck table in a plane direction of the holding surface, overlapThe region is characterized by having a scattering portion formed therein that prevents the fluorescence from the holding surface from being collected on the light receiving portion. In the laser processing apparatus, the scattering section may include a scattering section corresponding to a SiC ingot of a first diameter and a scattering section corresponding to a SiC ingot of a second diameter larger than the first diameter. [Effects of the Invention]

[0014] The present invention has an effect of suppressing errors in the inspection results of the facet region of a SiC ingot. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a laser processing device according to the first embodiment. [Figure 2] FIG. 2 is a plan view of a SiC ingot to be processed by the laser processing apparatus shown in FIG. [Figure 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. [Figure 5] 5 is a plan view of the chuck table of the laser processing apparatus shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a cross-sectional view that schematically shows a Facet inspection unit of the laser processing apparatus shown in FIG. [Figure 8] FIG. 8 is a side view, partially in cross section, showing the laser processing apparatus shown in FIG. 1 holding an SiC ingot on the chuck table. [Figure 9] FIG. 9 is a plan view showing an example of a facet region of the SiC ingot shown in FIG. [Figure 10] FIG. 10 is a cross-sectional view of a main part of the chuck table holding the SiC ingot shown in FIG. [Figure 11] FIG. 11 is a diagram showing an example of XY coordinates of the outer edge of the Facet region shown in FIG. [Figure 12] FIG. 12 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 13] FIG. 13 is a cross-sectional view showing a state in which the laser processing apparatus shown in FIG. 1 forms a peeling layer on a SiC ingot. [Figure 14] FIG. 14 is a cross-sectional view showing a state in which the laser processing apparatus shown in FIG. 1 moves the condenser lens up and down when forming a peeling layer on a SiC ingot. [Figure 15] FIG. 15 is a cross-sectional view of a chuck table of a laser processing apparatus according to a first modification of the first embodiment. [Figure 16] FIG. 16 is a cross-sectional view of a main part of a chuck table holding an SiC ingot in a laser processing apparatus according to a first modification of the first embodiment. [Figure 17] FIG. 17 is a diagram schematically showing the configuration of a Facet inspection unit and the like of a laser processing apparatus according to Modification 2 of Embodiment 1. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0017] [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 an example of the configuration of the laser processing apparatus according to the first embodiment. FIG. 2 is a plan view of a SiC ingot that is an object 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 portion of the SiC ingot shown in FIG. 2. FIG. 5 is a plan view of a chuck table of the laser processing apparatus shown in FIG. 1. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. FIG. 7 is a cross-sectional view schematically showing a Facet inspection unit of the laser processing apparatus shown in FIG. 1.

[0018] (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 Figs. 2 and 3, which is the object to be processed by the laser processing apparatus 1 according to the first embodiment, is made of SiC (silicon carbide) and is formed in a cylindrical shape as a whole in the first embodiment. In the first embodiment, the SiC ingot 200 is a hexagonal single crystal SiC ingot.

[0019] 2 and 3, the SiC ingot 200 has a first surface 201 that is a circular top surface, a second surface 202 that is a circular back surface of the first surface 201, and a peripheral surface 203 that is continuous with the outer edges of the first surface 201 and the second surface 202. The SiC ingot 200 also has a first orientation flat 204 on the peripheral surface 203 that indicates the crystal orientation of the SiC ingot 200, and a second orientation flat 205 that is perpendicular to the first orientation flat 204 and indicates the crystal orientation of the SiC ingot 200. The orientation flats 204 and 205 are flat planes that form straight lines in a plan view of the SiC ingot 200. A length 204-1 of the first orientation flat 204 is longer than a length 205-1 of the second orientation flat 205.

[0020] The SiC ingot 200 also has a C-axis 208 tilted at an off angle α in a tilt direction 207 toward the second orientation flat 205 with respect to a perpendicular 206 to the first surface 201, and a c-plane 209 perpendicular to the C-axis 208. The c-plane 209 is tilted at an off angle α with respect to the first surface 201 of the SiC ingot 200. The tilt direction 207 of the C-axis 208 from the perpendicular 206 is perpendicular to the extension direction of the second orientation flat 205 and is parallel to the first orientation flat 204.

[0021] 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 the range of, for example, 1° to 6°.

[0022] Furthermore, the SiC ingot 200 is generally doped with impurities such as nitrogen to impart electrical conductivity. For this reason, the SiC ingot 200 is not uniformly doped with such impurities, and a region 217 with a different crystal structure called a facet (hereinafter referred to as the facet region and shown with hatched lines in FIG. 2 ) may be formed during the growth process of the SiC single crystal. The impurity concentration in the facet region 217 is higher than that in other regions 218 (hereinafter referred to as the non-facet region and shown with a white background in FIG. 2 ). In this way, the facet region 217 has a different impurity concentration from the non-facet region 218. The facet region 217 has a higher refractive index and a higher energy absorption rate than the non-facet region 218.

[0023] Furthermore, first surface 201 of SiC ingot 200 is ground by a grinding device and then polished by a polishing device to form first surface 201 into a mirror finish. A portion of SiC ingot 200 on the side of first surface 201 is peeled off, and the peeled portion is produced into wafer 220 shown in Fig. 4. Furthermore, there are multiple types of SiC ingots 200 with different diameters 210.

[0024] The wafer 220 shown in FIG. 4 is manufactured by separating a portion including the first surface 201 of the SiC ingot 200 as the wafer 220, and then performing grinding, polishing, and the like on the separated surface 221 separated from the SiC ingot 200. After the wafer 220 is separated 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.

[0025] 2 and 3, after the delamination layer 211 shown in FIG. 3 is formed, a portion of the SiC ingot 200, i.e., the wafer 220 to be produced, is separated and delaminated starting from the delamination layer 211. The delamination layer 211 is formed by the laser processing apparatus 1 according to the first embodiment. The delamination surface 212 of the SiC ingot 200 from which the wafer 220 has been delaminated is formed into a mirror surface by grinding and polishing, and the delamination surface 212 is formed on the first surface 201. The delamination layer 211 is then formed again, and the wafer 220 is delaminated. In this way, the thickness of the SiC ingot 200 becomes thinner as the wafer 220 is delaminated, and the delamination layer 211 is formed until the predetermined thickness is reached, and the wafer 220 is delaminated.

[0026] (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. In the first embodiment, the laser processing apparatus 1 also serves as an inspection apparatus that inspects a facet region 217 of the SiC ingot 200. As shown in FIG. 1 , the laser processing apparatus 1 includes a chuck table 10 that holds the SiC ingot 200 on a holding surface 11, a laser processing unit 20, a moving unit 30, an imaging unit 40, a facet inspection unit 50, and a control unit 100.

[0027] 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, 5 and 6, the chuck table 10 includes a circular 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.

[0028] In the first embodiment, the base 13 is made of a metal such as stainless steel, is a non-porous body with no air permeability, and is formed in the shape of a thick disk. The base 13 is installed on the rotary movement unit 33 of the movement unit 30. As shown in FIGS. 5 and 6 , the base 13 has an outer diameter larger than that of the SiC ingot 200, and is provided with a recess 132 in the center of the upper surface 131 to which the porous plate 12 is attached. When the porous plate 12 is attached in the recess 132, the upper surface 131 of the base 13 is positioned on the same plane as the holding surface 11.

[0029] The recess 132 has a circular planar shape, an outer diameter larger than the outer diameter of the SiC ingot 200, and is positioned coaxially with the base 13. The recess 132 has a bottom surface 134 provided with a plurality of concentric suction grooves 133 and connecting suction grooves (not shown) that communicate between the suction grooves 133. These suction grooves 133 are recessed from the bottom surface 134 of the recess 132. Furthermore, these suction grooves 133 communicate with communicating passages 135 that open to the bottom surface 134 of the recess 132.

[0030] The communication passage 135 is connected to a suction passage 137 that is connected to a suction source 14 such as an ejector and that 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 of the base 13, the negative pressure from the suction source 14 acts on the porous plate 12 fitted in the recess 132, thereby sucking the holding surface 11 of the porous plate 12. When the base 13 is placed on the rotational transfer 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 transfer unit 33 and fixed.

[0031] The porous plate 12 is a disk-shaped, porous body having air permeability, with an outer diameter larger than that of the SiC ingot 200 and equal to the inner diameter of the recess 132. The porous plate 12 is fixed within 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 the 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 the on-off valve 136 is opened and negative pressure from the suction source 14 acts, the porous plate 12 suction-holds the SiC ingot 200 on the holding surface 11.

[0033] In the first embodiment, the porous plate 12 is formed by firing and connecting together 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. That is, the holding surface 11 of the chuck table 10 is formed of glass. Each glass particle is spherical and has a roughly uniform particle size. It is preferable that the glass particles are dense particles that do not contain air bubbles.

[0034] 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. Furthermore, 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).

[0035] In embodiment 1, the porous plate 12 is a porous body formed by connecting multiple glass particles together, but in the present invention, it may also be a porous body such as porous ceramics that has aggregate, such as 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.

[0036] 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.

[0037] Furthermore, the chuck table 10 is rotated by the rotary movement unit 33 of the movement unit 30 about an axis that is perpendicular to the holding surface 11 and parallel to the Z-axis direction that is parallel to the vertical direction. The chuck table 10, together with the rotary movement unit 33, is moved in the X-axis direction that is parallel to the horizontal direction by the X-axis movement unit 31 of the movement unit 30, and is moved in the Y-axis direction that 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 movement unit 30 between a processing area below the laser processing unit 20 and a load-in / load-out area that is away from below the laser processing unit 20 and where the wafer 220 is loaded and unloaded.

[0038] Scattering portions 111 are formed in regions of holding surface 11 of chuck table 10 that correspond to the outer peripheral edge of SiC ingot 200. The region of holding surface 11 of chuck table 10 that corresponds to the outer peripheral edge of SiC ingot 200 refers to a region that overlaps with the outer peripheral edge of SiC ingot 200 held on holding surface 11.

[0039] In the first embodiment, the scattering section 111 has a planar shape that follows the outer edge of the SiC ingot 200 held on the holding surface 11 and is a groove that is recessed from the holding surface 11. The scattering section 111 has a bottom surface 112 that is parallel to the holding surface 11 of the chuck table 10 and is formed lower than the holding surface 11. For this reason, the scattering section 111 includes the bottom surface 112, which is an area formed lower than the holding surface 11 of the chuck table 10. The scattering section 111 has an inner peripheral surface 113 that is arranged inside the SiC ingot 200 relative to the outer peripheral edge of the SiC ingot 200 held on the holding surface 11, and an outer peripheral surface 114 that is arranged outside the SiC ingot 200 relative to the outer peripheral edge of the SiC ingot 200 held on the holding surface 11. In the first embodiment, the chuck table 10 is provided with, as scattering sections 111, a scattering section 111 adapted to accommodate an SiC ingot 200 having a diameter 210 of 6 inches and a scattering section 111 adapted to accommodate an SiC ingot 200 having a diameter 210 of 8 inches.

[0040] The laser processing unit 20 positions a focal point 22 (shown in Figure 13) of a pulsed laser beam 21 having a wavelength that is transparent to the SiC ingot 200 on the SiC ingot 200 held on the chuck table 10 at a depth 213 corresponding to the thickness 222 (shown in Figure 4) of the 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 peeling layer 211 in which a crack 215 extends along the c-plane 209.

[0041] Furthermore, when the SiC ingot 200 is moved relative to the laser beam 21 along the second orientation flat 205 and irradiated with a pulsed laser beam 21 of a wavelength that is transparent to the SiC ingot 200, as shown in Figures 12 and 13, the irradiation of the pulsed laser beam 21 causes the SiC to separate 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 processing 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.

[0042] In the first embodiment, as shown in Fig. 1, the laser processing unit 20 is supported at the tip of a support 4 that is supported on an upright wall 3 that stands upright from the apparatus main body 2. The laser processing unit 20 includes an oscillator that emits a pulsed laser beam 21 for processing the SiC ingot 200, and a condenser 23 that focuses the laser beam 21 emitted 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.

[0043] The condenser 23 includes a condenser lens (not shown) that is 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).

[0044] The moving unit 30 moves the Facet inspection unit 50 and the laser processing unit 20 relative to the chuck table 10 along the X-axis and Y-axis directions, which are the surface directions of the holding surface 11. In the first embodiment, the moving unit 30 moves the chuck table 10 relatively around axes parallel to the X-axis, Y-axis, and Z-axis directions. The X-axis and Y-axis directions 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.

[0045] 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 that rotates the chuck table 10 around an axis parallel to the Z-axis direction.

[0046] The Y-axis moving unit 32 is a unit that indexes and feeds the chuck table 10 and the laser processing unit 20 relative to one another. 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 that the moving plate 5 is movable in the Y-axis direction.

[0047] The X-axis moving unit 31 is a unit that relatively moves the chuck table 10 and the laser processing 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 rotational moving unit 33 that rotates the chuck table 10 around an axis parallel to the Z-axis direction, so that the second moving plate 6 can move freely in the X-axis direction.

[0048] The X-axis moving unit 31 and the Y-axis moving unit 32 are equipped with 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 well-known guide rails that support the moving plates 5 and 6 so that they can move freely in the X-axis or Y-axis direction.

[0049] The laser processing device 1 also includes an X-axis position detection unit 34 for detecting the position of the chuck table 10 in the X-axis direction, a Y-axis position detection unit 35 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 processing unit 20 in the Z-axis direction. Each of the position detection units 34, 35 outputs the detection results to the control unit 100.

[0050] In the first embodiment, the position in the X-axis direction and the Y-axis direction of the chuck table 10 of the laser processing apparatus 1 are determined based on a predetermined reference position (not shown). In the first embodiment, the position in the X-axis direction and the position in the Y-axis direction are determined by the distance in the X-axis direction and the Y-axis direction from the reference position. In the first embodiment, the XY coordinates represented by the X-axis direction and the Y-axis direction of the laser processing apparatus 1 (coordinates indicated by the distance in the X-axis direction from the reference position indicating the position in the X-axis direction and the distance in the Y-axis direction from the reference position indicating the position in the Y-axis direction) can indicate any position in the X-axis direction and the Y-axis direction of the SiC ingot 200 held on the holding surface 11 of the chuck table 10.

[0051] The imaging unit 40 includes a plurality of imaging elements that capture images of the SiC ingot 200 held on the chuck table 10. The imaging elements are, for example, CCD (Charge-Coupled Device) imaging elements or CMOS (Complementary MOS) imaging elements. The imaging unit 40 captures images of the SiC ingot 200 held on the holding surface 11 of the chuck table 10, acquires images for performing alignment between the SiC ingot 200 and the laser processing unit 20, and outputs the acquired images to the control unit 100. In the first embodiment, the imaging unit 40 is supported on the tip of the support 4 and is positioned so as to be aligned in the X-axis direction with the focusing lens of the laser processing unit 20.

[0052] The Facet inspection unit 50 irradiates the SiC ingot 200 with inspection light 562 of a predetermined wavelength from the first surface 201 of the SiC ingot 200 and detects the number of photons of fluorescence 563 specific to SiC.

[0053] 7, the Facet inspection unit 50 includes a case 51 supported on the tip of a support 4, an inspection light emitting unit 52, and a light receiving unit 53. The case 51 blocks light having wavelengths equal to or greater than a first wavelength range (e.g., 750 nm), and is formed in a box shape with an opening at the bottom.

[0054] Inspection light irradiator 52 irradiates inspection light 562 onto first surface 201 of SiC ingot 200 held on chuck table 10. Inspection light irradiator 52 includes: light source 65 that oscillates excitation light 561 at a low output (e.g., 0.1 W) that is low enough not to perform laser processing on SiC ingot 200; dichroic mirror 54 that reflects inspection light 562, which is light of the excitation light 561 oscillated from light source 65 and has a wavelength in a second wavelength range (e.g., 365 nm to 375 nm) that is absorbed by SiC ingot 200, and transmits light of wavelengths outside the second wavelength range; and condenser lens 55 that collects inspection light 562 reflected by dichroic mirror 54 and irradiates first surface 201 of SiC ingot 200 with the collected inspection light.

[0055] The light source 65, the dichroic mirror 54, and the condenser lens 55 are disposed within the case 51. The light source 65 has, for example, a GaN-based light-emitting element, and irradiates the dichroic mirror 54 with excitation light 561 including light of a wavelength (for example, 365 nm) that is absorbed by the SiC ingot 200.

[0056] When SiC ingot 200 is irradiated with inspection light 562 in the second wavelength range, it absorbs this inspection light 562 and is excited by inspection light 562 to generate fluorescence 563. For example, if inspection light 562 has a wavelength of 365 nm, inspection light 562 penetrates to a depth of about 10 μm from first surface 201 of SiC ingot 200. Then, fluorescence 563 is generated from a plate-shaped region with a thickness of about 10 μm on the first surface 201 side of SiC ingot 200.

[0057] Light receiving unit 53 collects and receives fluorescence 563 generated when SiC ingot 200 is excited by inspection light 562. Light receiving unit 53 includes a filter 57 and a light receiving unit 58 arranged inside case 51. Filter 57 is arranged between condenser lens 55 and light receiving unit 58, and includes an IR filter that transmits light 564 having a wavelength in a first wavelength range out of fluorescence 563 generated by SiC ingot 200 and transmitted through condenser lens 55, and blocks light having wavelengths outside the first wavelength range.

[0058] The light receiving unit 58 receives light 564 having a wavelength in the first wavelength range that is transmitted by the filter 57 and is part of the fluorescence 563 generated from the SiC ingot 200 and transmitted through the condenser lens 55, generates a signal indicating the number of photons in the received light 564, and outputs the generated signal to the control unit 100. Here, the number of photons decreases as the impurity concentration increases in the region of the SiC ingot 200 irradiated with the inspection light 562. That is, the number of photons in the light 564 from the facet region 217 is smaller than the number of photons in the light 564 from the non-facet region 218.

[0059] Furthermore, although not shown, the Facet inspection unit 50 includes a focal point position adjustment means that raises and lowers the case 51 to adjust the position of the focal point of the inspection light 562 in the Z-axis direction, and this focal point position adjustment means includes, for example, a ball screw connected to the case 51 and extending in the Z-axis direction, and a motor that rotates this ball screw.

[0060] The control unit 100 controls each of the above-mentioned components of the laser processing apparatus 1, causing 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 with a microprocessor such as a CPU (central processing unit), a storage device with memory such as a ROM (read only memory) or RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit 100 performs arithmetic processing in accordance with 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.

[0061] The control unit 100 is also connected to a display unit 110, which is configured with a liquid crystal display device or the like that displays the status of the machining operation, images, etc., and an input unit (not shown) that the 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.

[0062] Next, the processing operation of the laser processing apparatus 1 configured as described above on the SiC ingot 200, i.e., the inspection operation of the SiC ingot 200, will be described. FIG. 8 is a side view, partially in cross section, showing the laser processing apparatus shown in FIG. 1 holding the SiC ingot on the chuck table. FIG. 9 is a plan view showing an example of the Facet region of the SiC ingot shown in FIG. 8. FIG. 10 is a cross-sectional view of a main part of the chuck table holding the SiC ingot shown in FIG. 8. FIG. 11 is a diagram showing an example of the XY coordinates of the outer edge of the Facet region shown in FIG. 9. FIG. 12 is a perspective view showing the laser processing apparatus shown in FIG. 1 forming a peeling layer on the SiC ingot. FIG. 13 is a cross-sectional view showing the laser processing apparatus shown in FIG. 1 forming a peeling layer on the SiC ingot. FIG. 14 is a cross-sectional view showing the laser processing apparatus shown in FIG. 1 raising and lowering a condenser lens when forming a peeling layer on the SiC ingot.

[0063] In the laser processing apparatus 1, the operator registers the processing conditions in the control unit 100, places the chuck table 10 on the rotary transfer unit 33, and places the second surface 202 of the SiC ingot 200 on the holding surface 11 of the chuck table 10. At this time, the SiC ingot 200 is positioned so that it is coaxial with the holding surface 11 and its outer periphery overlaps the scattering section 111. 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.

[0064] 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. 8, the second surface 202 of the SiC ingot 200 is suction-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 below the imaging unit 40, and causes the imaging unit 40 to capture an image of the SiC ingot 200.

[0065] Based on the image of the SiC ingot 200 captured by the imaging unit 40, the control unit 100 of the laser processing apparatus 1 adjusts the orientation of the chuck table 10 around its axis using the rotational movement unit 33, so that the second orientation flat 205 is parallel to the X-axis direction, the direction perpendicular to the inclination direction 207 is parallel to the X-axis direction, and the inclination direction 207 is parallel to the Y-axis direction, as shown in Figure 9.

[0066] Next, the control unit 100 of the laser processing apparatus 1 controls the moving unit 30 to relatively move the Facet inspection 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 inspection light 562 at predetermined intervals, and detects the number of photons of light 564 that has passed through the filter 57 out of the fluorescence 563 from the first surface 201 of the SiC ingot 200 at predetermined intervals with the light receiving unit 58. At this time, the excitation light 561 emitted from the light source 65 is reflected by the dichroic mirror 54 as inspection light 562 in the second wavelength range, which is guided to the condenser lens 55 and condensed by the condenser lens 55 to be irradiated onto the first surface 201 of the SiC ingot 200.

[0067] When inspection light 562 is irradiated onto first surface 201 of SiC ingot 200, SiC ingot 200 generates fluorescence 563 having a wavelength different from that of inspection light 562 (for example, a wavelength of 750 nm or more), and fluorescence 563 is emitted from SiC ingot 200. After fluorescence 563 passes through condenser lens 55 and dichroic mirror 54, only light 564 in the first wavelength range passes through filter 57. Light 564 transmitted through filter 57 is received by light-receiving unit 58, which detects the number of photons in light 564. Light-receiving unit 58 outputs a signal corresponding to the number of photons in received light 564 to control unit 100.

[0068] When the inspection light 562 is irradiated onto the SiC ingot 200 held on the chuck table 10, depending on the thickness of the SiC ingot 200, the chuck table 10 may also generate fluorescence 563 and emit the fluorescence 563 from the holding surface 11. In this case, the chuck table 10 of the laser processing apparatus 1 according to the first embodiment is provided with a scattering section 111 in an area of ​​the holding surface 11 corresponding to the outer periphery of the SiC ingot 200. Because the scattering section 111 is a groove recessed from the holding surface 11, as shown in FIG. 10 , the fluorescence 563 emitted from the bottom surface 112 of the scattering section 111 is scattered by being reflected by the inner circumferential surface 113 and the outer circumferential surface 114 of the scattering section 111. For this reason, in the laser processing apparatus 1 according to the first embodiment, the scattering section 111 prevents light 564 of the fluorescence 563 generated by the chuck table 10 and emitted from the holding surface 11 from being received by the light-receiving unit 58 of the Facet inspection unit 50.

[0069] The control unit 100 calculates the XY coordinates of the position where the inspection light 562 is irradiated on the SiC ingot 200 held on the chuck table 10 based on the position of the chuck table 10 detected by each position detection unit 34, 35, and stores the calculated XY coordinates of the position where the inspection light 562 is irradiated on the SiC ingot 200 held on the chuck table 10 in correspondence with the number of photons of the light 564 in the storage device.

[0070] The control unit 100 stores the XY coordinates of the position of the SiC ingot 200 held on the chuck table 10 where the inspection light 562 is irradiated and the number of photons of the light 564 stored in the storage device, and calculates the XY coordinates (XY coordinates) of the region where the number of photons of the light 564 is equal to or less than a predetermined value, that is, the XY coordinates (XY coordinates) of each position 217-1, 217-2, 217-3, . . . 217-N shown in FIG. 9 on the outer edge of the facet region 217. 217-1 ,Y 217-1 ), (X 217-2 ,Y 217-2 ), (X 217-3 ,Y 217-3 )···(X 217-N ,Y 217-N) is calculated as shown in FIG. 11, for example. Note that the positions 217-1, 217-2, 217-3, . . . 217-N shown in FIG. 11 are the positions 217-1, 217-2, 217-3, . . . 217-N shown in FIG. 9. For example, as shown in FIG. 11, the control unit 100 calculates the XY coordinates (X 217-1 ,Y 217-1 ), (X 217-2 ,Y 217-2 ), (X 217-3 ,Y 217-3 )···(X 217-N ,Y 217-N ) is temporarily stored in a storage device.

[0071] During the processing operation, the control unit 100 of the laser processing apparatus 1 controls the movement unit 30 based on the image of the SiC ingot 200 captured by the imaging unit 40 to adjust the relative positions of the SiC ingot 200 and the condenser 23 of the laser processing unit 20, so that in the first embodiment, the outer edge of the SiC ingot 200 closest 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 apparatus 1 aligns the second orientation flat 205 parallel to the X-axis direction, aligns the direction perpendicular to the tilt direction 207 parallel to the X-axis direction, and aligns the tilt direction 207 parallel to the Y-axis direction.

[0072] In the processing operation, the control unit 100 of the laser processing apparatus 1 adjusts the position of the condenser 23 in the Z-axis direction using the condenser moving unit, and positions the condenser 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. 12 , the control unit 100 of the laser processing apparatus 1 irradiates the SiC ingot 200 with the laser beam 21 of a wavelength that is transparent to SiC from the condenser 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.

[0073] As shown in Figure 13, when a laser beam 21 is irradiated onto a SiC ingot 200, the SiC separates into Si (silicon) and C (carbon), and the next pulse of laser beam 21 is absorbed by the previously formed C, forming a modified portion 214 where the SiC separates into Si and C in a chain reaction, and a peeling layer 211 including a crack 215 extending from the modified portion 214 along the c-plane 209.

[0074] After forming the peeling layer 211 over the entire length in the X-axis direction of the outer edge of the SiC ingot 200 closest to the second orientation flat 205, the control unit 100 of the laser processing apparatus 1 causes the Y-axis movement unit 32 to move 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 processing unit 20 moves toward the center of the first surface 201 of the SiC ingot 200 (hereinafter referred to as index feed). The control unit 100 of the laser processing apparatus 1 alternates between the irradiation of the laser beam 21 while moving the chuck table 10 in the X-axis direction by the X-axis movement unit 31 and the index feed until the peeling layer 211 is formed over the entire lower surface of the first surface 201, thereby completing the processing operation.

[0075] As a result, in the SiC ingot 200, a peeled layer 211 having reduced strength compared to other portions, including modified portions 214 where SiC is separated into Si and C and cracks 215, is formed from the first surface 201 to a depth 213 corresponding to the thickness 222 of the wafer 220 for each index feed movement distance 26. In the SiC ingot 200, a peeled layer 211 is formed from the first surface 201 to a depth 213 corresponding to the thickness 222 of the wafer 220 over the entire length in the direction parallel to the first orientation flat 204 for each index feed movement distance.

[0076] In the processing operation, the control unit 100 of the laser processing device 1 calculates the position where the laser processing unit 20 of the SiC ingot 200 held on the chuck table 10 is irradiating the laser beam 21 from the detection results of the position detection units 34 and 35, and calculates the XY coordinates (X and Y coordinates) of each position 217-1, 217-2, 217-3, . . . 217-N of the outer edge of the Facet area 217 stored in the storage device. 217-1 ,Y 217-1 ), (X 217-2 ,Y 217-2 ), (X 217-3 ,Y 217-3 )···(X 217-N ,Y 217-N ) to determine whether or not to irradiate the Facet region 217 with the laser beam 21.

[0077] During the processing operation, when the control unit 100 of the laser processing device 1 determines that the laser beam 21 should be irradiated onto the facet region 217, it controls the focal point moving unit to increase the energy of the laser beam 21 when irradiating the facet region 217 and to raise the position of the condenser 23, relative to the energy of the laser beam 21 and the position of the condenser 23 when irradiating the laser beam 21 onto the non-facet region 218.

[0078] In the laser processing apparatus 1, the refractive index of the facet region 217 is higher than that of the non-facet region 218, and by controlling as described above, the depth 213 of the focal point 22 can be made substantially the same in the facet region 217 and the non-facet region 218, as shown in Fig. 14, and the depth of the peeling layer 211 formed in the facet region 217 and the non-facet region 218 can be made substantially uniform. Furthermore, although the facet region 217 has a higher energy absorption rate than the non-facet region 218, by increasing the energy of the laser beam 21 irradiated onto the facet region 217 to be higher than the energy of the laser beam 21 irradiated onto the non-facet region 218, the quality of the peeling layer 211 formed in the facet region 217 and the non-facet region 218 can be made uniform.

[0079] As described above, the laser processing apparatus 1 according to the first embodiment forms the scattering portion 111 in a region of the holding surface 11 of the chuck table 10 corresponding to the outer periphery of the SiC ingot 200. This ensures that even if the thickness of the SiC ingot 200 decreases and the facet region 217 approaches the holding surface 11, there is a difference in height between the second surface 202, which is the underside of the SiC ingot 200, and the bottom surface 112 of the scattering portion 111. Therefore, the laser processing apparatus 1 according to the first embodiment can particularly prevent the light receiving unit 58 from receiving light 564 of the fluorescence 563 on the holding surface 11 near the outer periphery of the SiC ingot 200, thereby suppressing the influence of the fluorescence 563 on the holding surface 11 near the outer periphery of the SiC ingot 200. As a result, the laser processing apparatus 1 according to the first embodiment exhibits the effect of preventing errors in the inspection results of the facet region 217 of the SiC ingot 200.

[0080] Furthermore, in the laser processing apparatus 1 according to the first embodiment, the porous plate 12 that forms the holding surface 11 of the chuck table 10 is made of glass porous (i.e., glass), and therefore the laser beam 21 for processing the porous plate 12 of the chuck table 10 can easily pass through. As a result, the laser processing apparatus 1 according to the first embodiment can also prevent the chuck table 10 from being processed by the laser beam 21.

[0081] 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 by volume 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).

[0082] As a result, the laser processing device 1 can suck and hold the SiC ingot 200 of various sizes having a diameter smaller than the outer diameter of the porous plate 12 onto the holding surface 11 without causing any hindrance to laser processing.

[0083] [Variation 1] A laser processing apparatus according to Modification 1 of Embodiment 1 of the present invention will be described with reference to the drawings. Fig. 15 is a cross-sectional view of a chuck table of the laser processing apparatus according to Modification 1 of Embodiment 1. Fig. 16 is a cross-sectional view of a main part of the chuck table holding a SiC ingot of the laser processing apparatus according to Modification 1 of Embodiment 1. In Figs. 15 and 16, the same parts as those in Embodiment 1 are designated by the same reference numerals, and description thereof will be omitted.

[0084] The laser processing apparatus 1 according to the first modification of the first embodiment is the same as the first embodiment, except that the scattering portion 111-1 of the chuck table 10 is not a groove, but is formed on the same plane as the holding surface 11, as shown schematically in FIG. 15, and the surface roughness (in the first modification, the arithmetic mean roughness) Ra is formed to be larger than the surface roughness Ra of the holding surface 11.

[0085] The scattering portion 111-1 of the chuck table 10 of the laser processing apparatus 1 according to the second modification is formed by sandblasting a part of the holding surface 11. In the first modification, the surface roughness Ra of the scattering portion 111 is not less than 10 μm and not more than 100 μm.

[0086] The laser processing apparatus 1 according to the first modification is provided with a scattering section 111-1 in an area corresponding to the outer periphery of the SiC ingot 200 on the holding surface 11 of the chuck table 10, and because the surface roughness Ra of the scattering section 111-1 is greater than the surface roughness of the holding surface 11, the fluorescence 563 emitted by the scattering section 111-1 is scattered on the surface of the scattering section 111-1. As a result, the laser processing apparatus 1 according to the first modification is prevented from receiving light 564 of the fluorescence 563 generated by the chuck table 10 and emitted from the holding surface 11 by the light receiving unit 58 of the Facet inspection unit 50.

[0087] The laser processing apparatus 1 of variant 1 forms a scattering section 111-1 in an area of ​​the holding surface 11 of the chuck table 10 corresponding to the outer peripheral edge of the SiC ingot 200, and therefore, similar to embodiment 1, can suppress the influence of the fluorescence 563 of the holding surface 11 near the outer peripheral edge of the SiC ingot 200, thereby achieving the effect of suppressing errors in the inspection results of the facet region 217 of the SiC ingot 200.

[0088] Furthermore, in the laser processing apparatus 1 according to variant example 1, the scattering section 111-1 is formed on the same plane as the holding surface 11 and has a surface roughness Ra of 100 μm or more. Therefore, the scattering section 111-1 scatters the fluorescence 563, thereby preventing the light receiving unit 58 of the Facet inspection unit 50 from receiving light 564 of the fluorescence 563 from the holding surface 11 near the outer edge of the SiC ingot 200.

[0089] [Variation 2] A laser processing apparatus according to Modification 2 of Embodiment 1 of the present invention will be described with reference to the drawings. Fig. 17 is a diagram schematically showing the configuration of a Facet inspection unit and the like of the laser processing apparatus according to Modification 2 of Embodiment 1. In Fig. 17, the same parts as those in Embodiment 1 are assigned the same reference numerals, and their description will be omitted.

[0090] As shown in FIG. 17, the Facet inspection unit 50-2 of the laser processing apparatus 1 according to the second modification of the first embodiment includes a case 51 supported on the tip of the support 4, an inspection light irradiator 52, and a light receiver 53.

[0091] In the second modification, the inspection light irradiation unit 52 includes a light source 65, a mirror 59, and a condenser lens 55. The mirror 59 is housed in the case 51 and reflects the excitation light 561 emitted by the light source 65 toward the condenser lens 55. The condenser lens 55 condenses the excitation light 561 from the light source 65 reflected by the mirror 59 as the inspection light 562 and irradiates the first surface 201 of the SiC ingot 200 with the inspection light 562.

[0092] In the second modification, the light receiving section 53 includes an annular elliptical mirror 60 disposed within the case 51 and having a reflecting surface 61 on the inside, a filter 57, and a light receiving unit 58. The elliptical mirror 60 is disposed closer to the holding surface 11 of the chuck table 10 than the condensing lens 55, and the reflecting surface 61 corresponds to a part of the curved surface of a spheroid obtained by rotating an ellipse 62 having a major axis extending in the vertical direction and a minor axis extending in the horizontal direction around the major axis.

[0093] The elliptical mirror 60 has two focal points 63, 64, and condenses light emitted from one of the focal points (for example, the focal point 63) to the other focal point (for example, the focal point 64). One focal point 63 of the elliptical mirror 60 is designed to approximately coincide with the focus of the condenser lens 55. The other focal point 64 of the elliptical mirror 60 is set at the light-receiving unit 58. The elliptical mirror 60 reflects the fluorescence 563 emitted by the SiC ingot 200 held on the chuck table 10 at the reflecting surface 61, passes the fluorescence through the filter 57, and then receives it at the light-receiving unit 58.

[0094] The laser processing apparatus 1 of the modified example 2 forms a scattering portion 111 in an area of ​​the holding surface 11 of the chuck table 10 corresponding to the outer peripheral edge of the SiC ingot 200, and therefore, similar to the embodiment 1, it is possible to suppress the influence of the fluorescence 563 of the holding surface 11 near the outer peripheral edge of the SiC ingot 200, thereby achieving the effect of suppressing errors in the inspection results of the facet region 217 of the SiC ingot 200.

[0095] Next, the inventors of the present invention set the width of scattering portion 111, which is a groove, to 1 mm to 3 mm, set the depth of scattering portion 111 to 0.5 mm to 2.0 mm, and irradiated SiC ingot 200 with laser beam 21 at a depth 213 and a width of 2 mm to form peeling layer 211, and confirmed that peeling layer 211 could be formed without any problems. Specifically, the inventors confirmed that peeling layer 211 could be formed without sinking of SiC ingot 200 along scattering portion 111, which is a groove.

[0096] The present invention is not limited to the above-described embodiment, and can be implemented in various modifications without departing from the gist of the present invention.

[0097] For example, in the above-described 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 any non-porous, non-air-permeable material, such as soda glass (soda-lime glass), borosilicate glass, or quartz glass, or may be made of ceramics. In this case, in the laser processing apparatus 1, the chuck table 10 is made of glass, not only the porous plate 12 but also the base 13, so that the chuck table 10 easily transmits the processing laser beam 21, and therefore it is possible to prevent the chuck table 10 from being processed by the laser beam.

[0098] Furthermore, in the present invention, it is preferable that at least the holding surface 11 of the porous plate 12 of the chuck table 10 of the laser processing apparatus 1 be formed in a color that absorbs the inspection light 41. A color 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 traditionally been used for the outer surface of chuck tables. The color that absorbs the inspection light 41 is preferably a dark color, which is a dark chromatic color with low brightness that includes achromatic dark gray or black, a deep dark color, or preferably black. Thus, colors that absorb the inspection light 41 include dark colors, deep dark colors, and black. The porous plate 12 is formed entirely in black, a color that absorbs the inspection light 41, by, for example, mixing black pigment such as carbon powder or mineral powder into glass particles or the like.

[0099] In the present invention, it is also preferable that the outer surface of the base 13 of the chuck table 10 in the laser processing device 1 be formed in a color that absorbs the inspection light 41 .

[0100] As described above, when the porous plate 12 and base 13 of the chuck table 10 are formed in a color that absorbs the inspection light 41, the laser processing apparatus 1 can suppress the fluorescence 563 generated by the chuck table 10, thereby achieving the effect of further reducing errors in the inspection results of the facet region 217 of the SiC ingot 200.

[0101] In addition, in the above-described embodiment, the laser processing apparatus 1 in the inspection device is equipped with the laser processing unit 20 and forms the peeling layer 211 on the SiC ingot 200. However, in the present invention, the inspection device may not be equipped with the laser processing unit 20, and may perform only the inspection of the Facet region 217 out of the formation of the peeling layer 211 and the inspection of the Facet region 217. [Explanation of symbols]

[0102] 1 Laser processing equipment (inspection equipment) 10 Chuck table 11 Holding surface 20 Laser processing unit 21 Laser beam 22 Focus point 30 Mobile Units 50 Facet Inspection Units 52 Inspection light irradiation unit 53 Light receiving part 111,111-1 Scatter part 200 SiC ingots 201 1st side (top side) 211 Peeling layer 213 depth 215 Crack 217 Facet area 561 Excitation light (inspection light) 562 Inspection Light 563 Fluorescence

Claims

1. An inspection device for inspecting facet regions of a SiC ingot having a circular flat first surface and a circular flat second surface on the back side of the first surface, the facet regions having different impurity concentrations, comprising: a chuck table that holds the SiC ingot on a holding surface; a facet inspection unit including an inspection light irradiating unit that irradiates inspection light onto the SiC ingot held on the chuck table, and a light receiving unit that collects and receives fluorescence generated by excitation with the inspection light; An inspection device in which a scattering portion is formed in the area where the outer edge of the SiC ingot overlaps with the holding surface of the chuck table, the scattering portion preventing the fluorescence from the holding surface from being concentrated on the light receiving portion.

2. An inspection device as described in claim 1, wherein the scattering section includes a scattering section corresponding to a SiC ingot of a first diameter and a scattering section corresponding to a SiC ingot of a second diameter larger than the first diameter.

3. 3. The inspection device according to claim 1, wherein the scattering portion is an area formed lower than the holding surface of the chuck table, or an uneven surface.

4. 4. The inspection device according to claim 1, wherein the holding surface of the chuck table is made of glass.

5. A laser processing device for forming a peeling layer on a SiC ingot having a circular flat first surface and a circular flat second surface on the back side of the first surface, a chuck table that holds the SiC ingot on a holding surface; a facet area inspection unit including an inspection light irradiating unit that irradiates inspection light onto the SiC ingot held on the chuck table, and a light receiving unit that collects and receives fluorescence emitted by the inspection light; a laser processing unit that irradiates the SiC ingot held on the chuck table with a laser beam, the laser beam having a wavelength that is transparent to the SiC ingot, with the focal point positioned at a depth from the top surface of the SiC ingot that corresponds to the thickness of the wafer to be produced, thereby forming a peeled layer in which cracks extend; and a moving unit that moves the facet area inspection unit and the laser processing unit relative to the chuck table in a surface direction of the holding surface, A laser processing apparatus in which a scattering portion is formed in the area where the outer edge of the SiC ingot overlaps with the holding surface of the chuck table, the scattering portion preventing the fluorescence from the holding surface from being concentrated on the light receiving portion.

6. A laser processing apparatus as described in Claim 5, wherein the scattering section includes a scattering section corresponding to a SiC ingot of a first diameter and a scattering section corresponding to a SiC ingot of a second diameter larger than the first diameter.

Images