Separation original point formation method and separation method

Abstract

To enable suppression of poor separation.SOLUTION: A separation original point formation method comprises: a holding step 301 of holding an ingot with a holding unit and exposing its first surface; a specification region setting step 304 of setting a Facet region on a first surface of the ingot; and a laser processing step 305 of forming a peeling layer in an inner part of the ingot by repeating a processing feeding for forming a band-like modification part in an inner part of the ingot by relatively moving a focal point to the ingot in an X-axis direction while radiating a laser beam toward a first surface in a state where the focal point is positioned at the inner part of the ingot and an index feeding for relatively moving the focal point to the ingot in a Y-axis direction after the processing feeding. In the laser processing step 305, an interval of the adjacent modification part in a Facet region is set to an interval that is narrower than the adjacent modification parts in a non-Facet region.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a separation starting point forming method and a separation method for forming a separation starting point for separating a workpiece into a first surface side and a second surface side.

Background Art

[0002] For example, a method has been proposed in which a laser beam is irradiated onto an ingot or a wafer made of, for example, a single crystal of SiC (silicon carbide) or silicon to form a separation starting point inside, and then the wafer is separated (see, for example, Patent Document 1 and Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, in a single crystal of SiC, a faceted region and a non-faceted region having different growth modes are formed during the growth process. The faceted region has a higher energy absorption rate than the non-faceted region. Therefore, in the faceted region, the intensity of the laser beam reaching the focusing point becomes weaker than that in the non-faceted region, and there is a risk that a sufficient separation layer cannot be formed in the faceted region, resulting in separation failure, and improvement is eagerly desired.

[0005] An object of the present invention is to provide a separation starting point forming method and a separation method capable of suppressing separation failure.

Means for Solving the Problems

[0006] In order to solve the above-described problems and achieve the object, a separation starting point forming method of the present invention is a separation starting point forming method for forming a separation starting point inside a workpiece for separating a workpiece having a first surface and a second surface on the back surface of the first surface into the first surface side and the second surface side, which includes: a holding step of holding the workpiece by a holding unit and exposing the first surface; a specific region setting step of setting a specific region on the first surface of the workpiece before or after performing the holding step; after performing the holding step and the specific region setting step, while positioning the condensing point of the laser beam inside the workpiece, irradiating the laser beam toward the first surface and relatively moving the condensing point in the machining feed direction with respect to the workpiece to form a strip-shaped modified portion inside the workpiece, a machining feed; an index feed of relatively moving the condensing point in the index feed direction orthogonal to the machining feed direction with respect to the workpiece after the machining feed; and a laser machining step of repeatedly performing the above to form a plurality of modified portions inside the workpiece and form a separation starting point including the plurality of modified portions inside the workpiece. In the laser machining step, the interval between adjacent modified portions in the specific region is set to be narrower than the interval between adjacent modified portions outside the specific region.

[0007] In the separation starting point forming method, the laser machining step includes: a first sub-step of repeatedly irradiating the laser beam from one end to the other end of the outer peripheral edge of the workpiece in the machining feed direction while relatively moving the condensing point, and then relatively moving the condensing point in the index feed direction; and a second sub-step of, before or after the first sub-step, repeatedly irradiating the laser beam from one end to the other end of the specific region in the machining feed direction while relatively moving the condensing point, and then relatively moving the condensing point in the index feed direction. In the first sub-step and the second sub-step, the laser beam may be irradiated at different positions in the index feed direction.

[0008] In the separation starting point forming method, in the first sub-step and the second sub-step, the condensing point may be relatively moved in the index feed direction by the same index amount.

[0009] In the separation starting point forming method, in the specific region setting step, the specific region may be set based on the optical characteristics of the workpiece.

[0010] The separation method of the present invention is a separation method for separating a workpiece having a first surface and a second surface on the back of the first surface into a first surface side and a second surface side, including a holding step of holding the workpiece with a holding unit to expose the first surface, a specific region setting step of setting a specific region on the first surface of the workpiece before or after performing the holding step, a processing feed step of forming a strip-shaped modified portion inside the workpiece by irradiating the first surface with a laser beam while positioning the condensing point of the laser beam inside the workpiece and relatively moving the condensing point in the processing feed direction with respect to the workpiece, and an index feed step of relatively moving the condensing point in the index feed direction orthogonal to the processing feed direction with respect to the workpiece after the processing feed, and repeating these steps to form a plurality of modified portions inside the workpiece and form a separation starting point including the plurality of modified portions inside the workpiece, and a separation step of separating the workpiece into the first surface side and the second surface side from the separation starting point after performing the laser processing step. In the laser processing step, the interval between adjacent modified portions in the specific region is set to be narrower than the interval between adjacent modified portions outside the specific region.

Advantages of the Invention

[0011] The present invention has the effect of suppressing separation defects.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] Embodiments (modes for carrying out) of the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[0014] 〔Embodiment 1〕 The separation starting point forming method and the separation method according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration example of a separation apparatus for carrying out the separation starting point forming method and the separation method according to Embodiment 1. FIG. 2 is a plan view of an ingot to be processed in the separation starting point forming method and the separation method according to Embodiment 1. FIG. 3 is a side view of the ingot shown in FIG. 2. FIG. 4 is a perspective view of a wafer manufactured by peeling off a part of the ingot shown in FIG. 2. FIG. 5 is a diagram schematically showing the configuration of the Facet region detection unit of the separation apparatus shown in FIG. 1.

[0015] (Ingot) The separation starting point forming method and the separation method according to Embodiment 1 are methods of laser processing an ingot 200 (corresponding to a workpiece) shown in FIG. 2 and the like by the separation apparatus 1 shown in FIG. 1. The ingot 200 shown in FIGS. 2 and 3, which is the processing target of the separation starting point forming method and the separation method according to Embodiment 1, is made of SiC (silicon carbide) and is formed in a columnar shape as a whole in Embodiment 1. In Embodiment 1, the ingot 200 is a hexagonal single crystal ingot.

[0016] As shown in FIGS. 2 and 3, the ingot 200 is formed in a circular shape and has a first surface 201 which is the upper surface, a second surface 202 formed in a circular shape on the back side of the first surface 201, and a peripheral surface 203 connecting the outer edge of the first surface 201 and the outer edge of the second surface 202. Further, the ingot 200 has a first orientation flat 204 indicating the crystal orientation of the ingot 200 on the peripheral surface 203, and a second orientation flat 205 which is orthogonal to the first orientation flat 204 and indicates the crystal orientation of the ingot 200. The orientation flats 204 and 205 are flat planes and form a straight line in the plan view of the ingot 200. The length 204-1 of the first orientation flat 204 is longer than the length 205-1 of the second orientation flat 205.

[0017] Also, the ingot 200 has a C axis 208 inclined by an off-angle α in an inclined direction 207 toward the second orientation flat 205 with respect to a perpendicular 206 of the first surface 201, and a c plane 209 orthogonal to the C axis 208. The c plane 209 is inclined by the off-angle α with respect to the first surface 201 of the ingot 200. The inclined direction 207 of the C axis 208 from the perpendicular 206 is orthogonal to the extension direction of the second orientation flat 205 and parallel to the first orientation flat 204.

[0018] The c plane 209 is set innumerably at the molecular level of the ingot 200 in the ingot 200. In Embodiment 1, the off-angle α is set to 1°, 4°, or 6°. However, in the present invention, the ingot 200 can be manufactured by freely setting the off-angle α in the range of, for example, 1° to 6°.

[0019] In addition, the ingot 200 is generally doped with impurities such as nitrogen to impart conductivity. For this reason, in the ingot 200, regions 217 (corresponding to specific regions, hereinafter referred to as Facet regions and indicated by parallel hatching in Fig. 2) with different crystal structures called Facets may be formed during the growth process of the SiC single crystal without such impurities being uniformly doped. The impurity concentration in the Facet region 217 is higher than that in the region 218 outside the Facet region 217 (hereinafter referred to as the non-Facet region and indicated by white areas in Fig. 2). Thus, 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.

[0020] In addition, the first surface 201 of the ingot 200 is ground by a grinding device or the like so that the first surface 201 is formed into a mirror surface. A part of the ingot 200 on the first surface 201 side is peeled off, and the peeled part is formed into the wafer 220 shown in Fig. 4. Also, there are a plurality of types of ingots 200 having different diameters 210.

[0021] The wafer 220 shown in Fig. 4 is manufactured by peeling off a part including the first surface 201 of the ingot 200 as the wafer 220 and subjecting the peeled surface 221 peeled off from the ingot 200 to grinding, polishing, etc. After being peeled off from the ingot 200, a device is formed on the surface of the wafer 220. In Embodiment 1, the device is a MOSFET (Metal-oxide-semiconductor Field-effect Transistor), MEMS (Micro Electro Mechanical Systems), or SBD (Schottky Barrier Diode), but in the present invention, the device is not limited to MOSFET, MEMS, and SBD. Note that the same parts as those of the ingot 200 of the wafer 220 are denoted by the same reference numerals and the description thereof is omitted.

[0022] The ingot 200 shown in FIGS. 2 and 3 is separated and peeled off from a part, that is, the wafer 220 to be produced, starting from the peeling layer 211 (corresponding to the separation starting point) shown in FIG. 3, by the separation device 1 shown in FIG. 1. Further, for the ingot 200, the peeled surface 212 from which the wafer 220 has been peeled is formed into a mirror surface by grinding or the like, the peeled surface 212 is formed on the first surface 201, the peeling layer 211 is formed again, and the wafer 220 is peeled off. In this way, as the wafer 220 is peeled off from the ingot 200, the thickness of the ingot 200 becomes thinner, and the peeling layer 211 is formed until the ingot 200 reaches a predetermined thickness, and the wafer 220 is peeled off.

[0023] In addition, in FIGS. 2 and 4, the boundary between the Facet region 217 and the non-Facet region 218 is shown, but this boundary line is a virtual line and does not exist in the actual ingot 200. The material of the ingot 200 is not limited to SiC, and may be LiTaO3 (lithium tantalate: LT), GaN (gallium nitride), or silicon. Further, one or both of the first orientation flat 204 and the second orientation flat 205 may not be provided on the peripheral surface of the ingot 200.

[0024] (Separation device) The separation device 1 shown in FIG. 1 is a device that separates and peels off a part, that is, the wafer 220 to be produced, starting from the peeling layer 211, from the ingot 200 shown in FIGS. 2 and 3 after the peeling layer 211 shown in FIG. 3 is formed in the ingot 200. That is, it is a device that forms a peeling layer 211 for separating the ingot 200 into the first surface 201 side and the second surface 202 side inside the ingot 200, and separates the ingot 200 into the first surface 201 side and the second surface 202 side starting from the peeling layer 211.

[0025] As shown in FIG. 1, the separation device 1 includes a holding unit 10 that holds an ingot 200 on a holding surface 11, a laser processing unit 20, an imaging unit 40, a Facet region detection unit 50, a grinding unit 60, a separation unit 70, and a control unit 100. Further, the separation device 1 includes a moving unit 30 that relatively moves the holding unit 10, the laser processing unit 20, the imaging unit 40, the Facet region detection unit 50, the grinding unit 60, and the separation unit 70 in an X-axis direction parallel to the horizontal direction and in a Y-axis direction parallel to the horizontal direction and orthogonal to the X-axis direction.

[0026] Note that the X-axis direction is a so-called processing feed direction in which the holding unit 10 is fed during laser processing of the ingot 200 by the separation device 1. The Y-axis direction is orthogonal to the X-axis direction and is a so-called index feed direction in which the holding unit 10 is index-fed during laser processing of the ingot 200 by the separation device 1.

[0027] The moving unit 30 includes an X-axis moving unit 31 that moves the holding unit 10 in the X-axis direction, a Y-axis moving unit 32 that moves the holding unit 10 in the Y-axis direction, and a rotational moving unit 33 that rotates the holding unit 10 around an axis parallel to the Z-axis direction.

[0028] The X-axis moving unit 31 is a unit that relatively feeds the holding unit 10, the laser processing unit 20, the imaging unit 40, the Facet region detection unit 50, the grinding unit 60, and the separation unit 70. In Embodiment 1, the X-axis moving unit 31 is installed on the device main body 2 of the separation device 1. The X-axis moving unit 31 movably supports a moving plate 3 that supports the Y-axis moving unit 32 in the X-axis direction.

[0029] The Y-axis moving unit 32 is a unit that relatively indexes the holding unit 10 and the laser processing unit 20, the imaging unit 40, the Facet region detection unit 50, the grinding unit 60, and the separation unit 70. The Y-axis moving unit 32 is installed on the moving plate 3. The Y-axis moving unit 32 movably supports a second moving plate 4 that supports a rotational moving unit 33 that rotates the holding unit 10 around an axis parallel to the Z-axis direction in the Y-axis direction.

[0030] The rotational moving unit 33 is installed on the second moving plate 4 and supports the holding unit 10. The X-axis moving unit 31 and the Y-axis moving unit 32 include a well-known ball screw rotatably provided around an axis, a well-known pulse motor that rotates the ball screw around the axis, and a well-known guide rail that movably supports the moving plates 3 and 4 in the X-axis direction or the Y-axis direction. The rotational moving unit 33 includes a motor or the like that rotates the holding unit 10 around an axis.

[0031] Further, the separation device 1 includes an X-axis direction position detection unit (not shown) for detecting the position of the holding unit 10 in the X-axis direction, a Y-axis direction position detection unit (not shown) for detecting the position of the holding unit 10 in the Y-axis direction, and a Z-axis direction position detection unit (not shown) for detecting the position of the condenser lens included in the laser processing unit 20 in the Z-axis direction. Each position detection unit outputs a detection result to the control unit 100.

[0032] In Embodiment 1, the position of the holding unit 10 of the separation device 1 in the X-axis direction and the Y-axis direction are determined based on a predetermined reference position (not shown). In Embodiment 1, the position in the X-axis direction and the position in the Y-axis direction are determined by the distances in the X-axis direction and the Y-axis direction from the reference position. In Embodiment 1, the XY coordinates (coordinates represented 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) represented by the X-axis direction and the Y-axis direction of the separation device 1 can indicate any position in the X-axis direction and the Y-axis direction of the ingot 200 held on the holding surface 11 of the holding unit 10.

[0033] The holding unit 10 is installed on the rotational movement unit 33 of the moving unit 30 and holds the ingot 200 with a holding surface 11 parallel to the horizontal direction. The holding unit 10 has a disk shape, and the holding surface 11 for holding the second surface 202 of the ingot 200 is formed of porous ceramic or the like. Further, the holding unit 10 is movably provided in the X-axis direction across the lower part of the separation unit 70, the lower part of the laser processing unit 20, the lower part of the imaging unit 40, the lower part of the Facet region detection unit 50, and the lower part of the grinding unit 60 by the X-axis movement unit 31, and is rotatably provided around an axis parallel to the Z-axis direction by the rotational movement unit 33.

[0034] The holding unit 10 has the holding surface 11 connected to a vacuum suction source (not shown), and by being sucked by the vacuum suction source, sucks and holds the second surface 202 of the ingot 200 placed on the holding surface 11.

[0035] The laser processing unit 20 positions the focus point of the pulsed laser beam 21 having a wavelength that is transmissive to the ingot 200 held by the holding unit 10 at a depth corresponding to the thickness 222 of the wafer 220 to be formed from the first surface 201 of the ingot 200, irradiates the ingot 200 with the laser beam 21, separates the SiC into Si and C, and forms a peeling layer 211 in which a crack 215 (shown in FIG. 11) extends along the c-plane 209.

[0036] Note that while the ingot 200 is relatively moved along the second orientation flat 205 with respect to the laser beam 21, when the ingot 200 is irradiated with a pulsed laser beam 21 having a wavelength that is transmissive to the ingot 200, as shown in FIG. 11, the SiC is separated into Si (silicon) and C (carbon) by the irradiation of the pulsed laser beam 21, and then the pulsed laser beam 21 to be irradiated next is absorbed by the C formed previously, and a modified portion 214 in which the SiC is successively separated into Si and C is formed inside the ingot 200 along the second orientation flat 205, and a crack 215 extending from the modified portion 214 along the c-plane 209 is generated. Thus, when the ingot 200 is irradiated with the pulsed laser beam 21 having a wavelength that is transmissive to the ingot 200, the laser processing unit 20 forms a separation layer 211 including the modified portion 214 and the crack 215 formed from the modified portion 214 along the c-plane 209 in the ingot 200.

[0037] In Embodiment 1, as shown in FIG. 1, the laser processing unit 20 is supported at the tip of a support column 6 whose base end is supported by a standing column 5 standing 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 ingot 200, and a condenser that condenses the laser beam 21 emitted from the oscillator onto the ingot 200 held on the holding surface 11 of the holding unit 10 to form the separation layer 211.

[0038] The condenser includes a condenser lens (not shown) disposed at a position facing the holding surface 11 of the holding unit 10 in the Z-axis direction. The condenser lens transmits the laser beam 21 emitted from the oscillator and condenses the laser beam 21 at the condensing point. Also, in Embodiment 1, the condenser is provided so as to be movable in the Z-axis direction by a condensing point moving unit (not shown).

[0039] The imaging unit 40 includes a plurality of imaging elements that image the ingot 200 held by the holding unit 10. The imaging elements are, for example, CCD (Charge-Coupled Device) imaging elements or CMOS (Complementary MOS) imaging elements. The imaging unit 40 images the ingot 200 held on the holding surface 11 of the holding unit 10, acquires an image for performing alignment to align the ingot 200 with the laser processing unit 20, and outputs the acquired image to the control unit 100. In Embodiment 1, the imaging unit 40 is supported at the tip of the column 6 and is arranged at a position aligned with the condenser lens of the laser processing unit 20 in the X-axis direction.

[0040] The Facet region detection unit 50 irradiates the first surface 201 of the ingot 200 with inspection light 542 having a predetermined wavelength and detects the luminance of the fluorescence 543 specific to SiC.

[0041] As shown in FIG. 5, the Facet region detection unit 50 includes a case 51 supported at the tip of the column 6, an inspection light irradiation unit 52, and a light receiving unit 53. The case 51 is formed in a box shape that blocks light having a wavelength equal to or longer than a first wavelength range (for example, 750 nm) and has an opening provided downward, and is supported at the tip of the column 6. The case 51 is arranged at a position aligned with the condenser lens of the laser processing unit 20 and the imaging unit 40 in the X-axis direction.

[0042] The inspection light irradiation unit 52 irradiates the first surface 201 of the ingot 200 held by the holding unit 10 with the inspection light 542. The inspection light irradiation unit 52 includes a light source 54 that oscillates excitation light 541 with a low output (for example, 0.1 W) that does not perform laser processing on the ingot 200, a dichroic mirror 55 that reflects the inspection light 542 having a wavelength in a second wavelength range (for example, 365 nm to 375 nm) that is absorbed by the ingot 200 among the excitation light 541 oscillated from the light source 54 and transmits light having a wavelength other than the second wavelength range, and a condenser lens 56 that condenses the inspection light 542 reflected by the dichroic mirror 55 and irradiates the first surface 201 of the ingot 200.

[0043] The light source 54, the dichroic mirror 55, and the condenser lens 56 are arranged in the case 51. The light source 54 has, for example, a GaN-based light-emitting element, and irradiates the dichroic mirror 55 with excitation light 541 including light having a wavelength (for example, 365 nm) that is absorbed by the ingot 200.

[0044] When the ingot 200 is irradiated with the inspection light 542 in the second wavelength range, the ingot 200 absorbs the inspection light 542 and generates fluorescence 543 excited by the inspection light 542. For example, if the wavelength of the inspection light 542 is 365 nm, the inspection light 542 penetrates from the first surface 201 of the ingot 200 to a depth of about 10 μm. Then, fluorescence 543 is generated from a plate-like region having a thickness of about 10 μm on the first surface 201 side of the ingot 200.

[0045] The light receiving unit 53 collects and receives the fluorescence 543 generated when the ingot 200 is excited by the inspection light 542. The light receiving unit 53 includes an annular elliptical mirror 59 disposed in the case 51 and having an inner reflecting surface 591, a filter 57 disposed in the case 51, and a light receiving unit 58.

[0046] The elliptical mirror 59 is disposed closer to the holding surface 11 of the holding unit 10 than the condenser lens 56, and the reflecting surface 591 corresponds to a part of the curved surface of a rotational ellipsoid obtained by rotating an ellipse 592 having a major axis extending in the vertical direction and a minor axis extending in the horizontal direction about the major axis.

[0047] The elliptical mirror 59 has two foci 593 and 594, and condenses light generated from one of them (for example, focus 593) to the other (for example, focus 594). One focus 593 of the elliptical mirror 59 is designed to generally coincide with the focus of the condenser lens 56. The other focus 594 of the elliptical mirror 59 is set to the light receiving unit 58. The elliptical mirror 59 reflects the fluorescence 543 generated by the ingot 200 held by the holding unit 10 by the reflecting surface 591, transmits it through the filter 57, and then causes it to be received by the light receiving unit 58.

[0048] The filter 57 is disposed between the condenser lens 56 and the light receiving unit 58, and includes an IR filter that transmits light 544 having a wavelength in a first wavelength range among the fluorescence 543 generated by the ingot 200 and transmitted through the condenser lens 56, and blocks light 544 having a wavelength other than the first wavelength range.

[0049] The light receiving unit 58 receives the light 544 having a wavelength in the first wavelength range transmitted by the filter 57 among the fluorescence 543 generated by the ingot 200 and transmitted through the condenser lens 56, generates a signal indicating the luminance of the received light 544, and outputs the generated signal to the control unit 100. Here, the luminance decreases as the concentration of impurities in the region where the inspection light 542 of the ingot 200 is irradiated is higher. That is, the luminance of the light 544 from the Facet region 217 is less than the luminance of the light 544 from the non-Facet region 218.

[0050] Although not shown, the Facet region detection unit 50 includes a condensing point position adjustment means for raising and lowering the case 51 to adjust the position of the condensing point of the inspection light 542 in the Z-axis direction. This condensing 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 for rotating this ball screw.

[0051] The grinding unit 60 includes a spindle motor 61, a spindle 62 rotated by the spindle motor 61 around an axis parallel to the Z-axis direction, a grinding wheel 63 attached to the lower end of the spindle 62, a grinding feed unit 64 for raising and lowering the spindle motor 61, the spindle 62, and the grinding wheel 63 in the Z-axis direction, and a Y-axis direction position changing unit 65 installed on the support column 6 and changing the position of each of the grinding feed unit 64, the spindle motor 61, the spindle 62, and the grinding wheel 63 in the Y-axis direction.

[0052] The grinding wheel 63 is arranged at a position aligned in the X-axis direction with the condenser lens of the laser processing unit 20, the imaging unit 40, and the Facet area detection unit 50. The grinding wheel 63 includes an annular wheel base 66 attached to the lower end of the spindle 62, and a plurality of grinding wheels 67 arranged annularly on the lower surface of the wheel base 66. That is, the grinding wheel 63 fixes a plurality of grinding wheels 67 at equal intervals in the circumferential direction of the wheel base 66.

[0053] The grinding wheel 67 is configured as a so-called segment grinding wheel formed by mixing abrasive grains such as diamond or CBN (Cubic Boron Nitride) into a binder (also referred to as a bonding material) made of metal, ceramics, resin, or the like to form a single mass.

[0054] The separation unit 70 includes a disc-shaped holding plate 71 that sucks and holds the first surface 201 of the ingot 200 held by the holding unit 10, ultrasonic vibration applying means (not shown) that applies ultrasonic vibration to the holding plate 71, and a lifting unit 72 that raises and lowers the holding plate 71 in the Z-axis direction. The holding plate 71 is arranged at a position aligned in the X-axis direction with the condenser lens of the laser processing unit 20, the imaging unit 40, the Facet area detection unit 50, and the grinding wheel 63 of the grinding unit 60. The lifting unit 72 is installed on a standing column 7 erected from the apparatus main body 2.

[0055] The control unit 100 controls the above-described components of the separation device 1 to cause the separation device 1 to perform a processing operation on the ingot 200. The control unit 100 is a computer having an arithmetic processing unit with 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 unit of the control unit 100 performs arithmetic processing according to a computer program stored in the storage device, and outputs a control signal for controlling the separation device 1 to the above-described components of the separation device 1 via the input / output interface device, thereby realizing the functions of the control unit 100.

[0056] In addition, the control unit 100 is connected to a display unit 110 constituted by a liquid crystal display device or the like that displays the state and image of the processing operation, and an input unit (not shown) used when an operator registers processing content information and the like. The input unit is constituted by at least one of a touch panel provided on the display unit 110 and an external input device such as a keyboard.

[0057] (Separation method) Next, the separation method according to Embodiment 1 will be described. The processing method according to Embodiment 1 is also a processing operation on the ingot 200 of the separation device 1 having the above-described configuration. FIG. 6 is a flowchart showing the flow of the separation method according to Embodiment 1.

[0058] The separation method according to Embodiment 1 is a method of separating and peeling a part, that is, a wafer 220 to be generated, starting from the peeling layer 211 after the peeling layer 211 is formed on the ingot 200. That is, a peeling layer 211 for separating the ingot 200 into the first surface 201 side and the second surface 202 side is formed inside the ingot 200, and the ingot 200 is separated into the first surface 201 side and the second surface 202 side starting from the peeling layer 211. As shown in FIG. 6, the separation method includes a holding step 301, a specific region setting step 304, a laser processing step 305, and a separation step 306.

[0059] (Holding Step) The holding step 301 is a step of holding the ingot 200 by the holding unit 10 and exposing the first surface 201. In Embodiment 1, in the holding step 301, the separation device 1 has its processing conditions registered in the control unit 100 by the operator, and the second surface 202 of the ingot 200 is placed on the holding surface 11 of the holding unit 10. The processing conditions include information indicating whether the first surface 201 of the ingot 200 is formed into a mirror surface by grinding the first surface 201 with a grinding device or the like. In Embodiment 1, in the holding step 301, when the control unit 100 of the separation device 1 receives an instruction to start the processing operation from the operator, it sucks and holds the second surface 202 of the ingot 200 on the holding surface 11 of the holding unit 10.

[0060] Thereafter, the separation device 1 determines whether grinding is necessary for the first surface 201 of the ingot 200 held by the holding unit 10 by the control unit 100 (step 302). Specifically, when the processing conditions include information that the first surface 201 of the ingot 200 is not formed into a mirror surface and the peeling layer 211 is first formed on the ingot 200, or when the peeling layer 211 is formed on the ingot 200 held by the holding unit 10 and the wafer 220 is peeled off and the peeled surface 212 is not formed into a mirror surface, it is determined that grinding is necessary for the first surface 201 of the ingot 200 held by the holding unit 10 (step 302: Yes). When the separation device 1 determines that grinding is necessary for the first surface 201 of the ingot 200 held by the holding unit 10 by the control unit 100 (step 302: Yes), it proceeds to the grinding step 303.

[0061] (Grinding step) The grinding step 303 is a step of grinding the first surface 201 of the ingot 200 held by suction on the holding surface 11 of the holding unit 10 with the grinding wheel 63. In Embodiment 1, in the grinding step 303, the separation device 1 controls the moving unit 30 and the Y-axis direction position changing unit 65 by the control unit 100 to position the holding unit 10 below the grinding wheel 63 of the grinding unit 60.

[0062] In Embodiment 1, in the grinding step 303, the separation device 1 supplies grinding water while the control unit 100 rotates the spindle 62 of the grinding unit 60 and the holding unit 10 around the axis, and the grinding feed unit 64 lowers the spindle 62 and the grinding wheel 63 to bring the grinding wheel 67 into contact with the first surface 201 of the ingot 200 and approach the holding unit 10 at a predetermined feed rate, thereby performing grinding on the first surface 201 of the ingot 200 with the grinding wheel 67. In Embodiment 1, in the grinding step 303, when the separation device 1 grinds the ingot 200 and thins the ingot 200 by a predetermined thickness, the control unit 100 controls the grinding feed unit 64 to raise the grinding wheel 63 and the like, stops the rotation of the spindle 62 and the holding unit 10 and the supply of grinding water, and ends the grinding step 303.

[0063] After the grinding step 303 is completed, or when the separation device 1 determines that the first surface 201 of the ingot 200 sucked and held by the holding unit 10 does not require grinding (step 302: No), it proceeds to the specific area setting step 304.

[0064] (Specific area setting step) FIG. 7 is a perspective view schematically showing the specific area setting step of the separation method shown in FIG. 6. FIG. 8 is a plan view showing an example of the Facet area of the SiC ingot shown in FIG. 7. FIG. 9 is a view showing an example of the XY coordinates of the outer edge of the Facet area shown in FIG. 8. The specific area setting step 304 is a step of setting the Facet area 217 on the first surface 201 of the ingot 200 before or after performing the holding step 301.

[0065] In Embodiment 1, in the specific area setting step 304, after the holding step 301, the control unit 100 of the separation device 1 controls the moving unit 30 to move the holding unit 10 below the imaging unit 40, and causes the imaging unit 40 to image the ingot 200. In Embodiment 1, in the specific area setting step 304, based on the image of the ingot 200 acquired by imaging with the imaging unit 40, the control unit 100 of the separation device 1 adjusts the orientation of the holding unit 10 around its axis with the rotation moving unit 33. As shown in FIGS. 7 and 8, the second orientation flat 205 is made parallel to the X-axis direction, the direction orthogonal to the inclination direction 207 is made parallel to the X-axis direction, and the inclination direction 207 is made parallel to the Y-axis direction.

[0066] In Embodiment 1, in the specific area setting step 304, the control unit 100 of the separation device 1 controls the moving unit 30 to relatively move the Facet area detection unit 50 and the holding unit 10 as shown in FIG. 7, while irradiating the first surface 201 of the ingot 200 held on the holding surface 11 of the holding unit 10 with inspection light 542 at predetermined intervals, and detecting the luminance of the light 544 transmitted through the filter 57 among the fluorescence 543 of the first surface 201 of the ingot 200 at predetermined intervals with the light receiving unit 58. At this time, the excitation light 541 oscillated from the light source 54 is reflected by the dichroic mirror 55 and guided to the condenser lens 56 as the inspection light 542 in the second wavelength range, and is condensed by the condenser lens 56 and irradiated onto the first surface 201 of the ingot 200.

[0067] When the inspection light 542 is irradiated onto the first surface 201 of the ingot 200, the ingot 200 generates fluorescence 543 having a wavelength different from that of the inspection light 542 (for example, a wavelength of 750 nm or more), and the fluorescence 543 is emitted from the ingot 200. After the fluorescence 543 is reflected by the reflecting surface 591 of the elliptical mirror 59, only the light 544 in the first wavelength range passes through the filter 57, the light 544 passing through the filter 57 is received by the light receiving unit 58, and the luminance of the light 544 is detected by the light receiving unit 58. The light receiving unit 58 outputs a signal corresponding to the luminance of the received light 544 to the control unit 100.

[0068] In Embodiment 1, in the specific region setting step 304, the control unit 100 of the separation device 1 alternately performs irradiation of inspection light 542 over the entire length of the ingot 200 in the X-axis direction while moving the holding unit 10 by the X-axis moving unit 31 in the X-axis direction, and so-called index feeding that moves the holding unit 10 at a predetermined interval in the Y-axis direction along the first orientation flat 204, and repeats until the luminance of fluorescence 543 at each predetermined interval is detected over the entire surface of the first surface 201 of the ingot 200.

[0069] In Embodiment 1, in the specific region setting step 304, the control unit 100 of the separation device 1 calculates the XY coordinates of the position irradiated with the inspection light 542 of the ingot 200 held by the holding unit 10 based on the position of the holding unit 10 detected by each position detection unit, etc., and associates and stores in the storage device the XY coordinates of the position irradiated with the inspection light 542 of the ingot 200 held by the calculated holding unit 10 and the luminance of the light 544.

[0070] In Embodiment 1, in the specific region setting step 304, the control unit 100 of the separation device 1, among the XY coordinates of the position irradiated with the inspection light 542 of the ingot 200 held by the holding unit 10 stored in the storage device and the luminance of the light 544, the region where the luminance of the light 544 is lower than a predetermined value, that is, 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 ) of each position 217-1, 217-2, 217-3 ··· 217-N shown in FIG. 8 at the outer edge of the Facet region 217 are calculated as shown in FIG. 9, for example.

[0071] Note that each position 217-1, 217-2, 217-3 ··· 217-N shown in FIG. 9 is the position 217-1, 217-2, 217-3 ··· 217-N shown in FIG. 8. The control unit 100, for example, as shown in FIG. 9, once stores 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 ) of each position 217-1, 217-2, 217-3 ··· 217-N on the outer edge of the calculated Facet area 217 in a storage device, and sets the position of the Facet area 217 on the first surface 201 of the ingot 200. Thus, in Embodiment 11, by setting the Facet area 217 based on the luminance of the light 544 in the specific area setting step 304, the Facet area 217 is set based on the optical identification of the ingot 200.

[0072] (Laser processing step) FIG. 10 is a perspective view schematically showing the laser processing step of the separation method shown in FIG. 6. FIG. 11 is a cross-sectional view schematically showing the surface layer of the first surface on which the separation layer of the ingot shown in FIG. 10 is formed. FIG. 12 is a plan view schematically showing the ingot after the first sub-step of the laser processing step shown in FIG. 10. FIG. 13 is a plan view schematically showing the path of irradiating the laser beam in the second sub-step of the laser processing step shown in FIG. 10.

[0073] After performing the holding step 301 and the specific area setting step 304, the laser processing step 305 irradiates the first surface 201 with the laser beam 21 while positioning the condensing point of the laser beam 21 inside the ingot 200, and relatively moves the condensing point in the X-axis direction, which is the processing feed direction with respect to the ingot 200, to form a strip-shaped modified portion 214 inside the ingot 200. After the processing feed, the index feed relatively moves the condensing point in the Y-axis direction, which is the index feed direction orthogonal to the X-axis direction with respect to the ingot 200. By repeating these operations, a plurality of modified portions 214 are formed inside the ingot 200, and a separation layer 211, which is a separation starting point including the plurality of modified portions 214, is formed inside the ingot 200.

[0074] In Embodiment 1, as shown in FIG. 6, the laser processing step 305 includes a first sub-step 3051 and a second sub-step 3052. The first sub-step 3051 is a step of relatively moving the condensing point while irradiating the laser beam 21 from one end to the other end of the outer peripheral edge of the ingot 200 in the X-axis direction, and then repeatedly relatively moving the condensing point in the Y-axis direction.

[0075] In Embodiment 1, in the first sub-step 3051, the control unit 100 of the separation device 1 adjusts the relative position between the ingot 200 and the condenser of the laser processing unit 20. In Embodiment 1, the outer edge portion of the ingot 200 near the second orientation flat 205 and the condenser 23 are opposed to each other along the Z-axis direction. In Embodiment 1, in the first sub-step 3051, the control unit 100 of the separation device 1 adjusts the Z-axis position of the condenser with the condensing point moving unit, and positions the condensing point of the laser beam 21 at a depth corresponding to the thickness 222 of the wafer 220 to be generated from the first surface 201 of the ingot 200.

[0076] In Embodiment 1, in the first sub-step 3051, as shown in FIG. 10, the control unit 100 of the separation device 1 irradiates the ingot 200 with a laser beam 21 having a wavelength that is transmissive to SiC from a condenser while processing and feeding the holding unit 10 at a predetermined processing feed rate along the X-axis direction, that is, along the second orientation flat 205.

[0077] As shown in FIG. 11, when the ingot 200 is irradiated with the laser beam 21, SiC is separated into Si (silicon) and C (carbon), and then the pulsed laser beam 21 to be irradiated next is absorbed by the C formed previously, and a modified portion 214 in which SiC is successively separated into Si and C, and a crack 215 extending from the modified portion 214 along the c-plane 209 are formed, and a peeling layer 211 is formed.

[0078] In Embodiment 1, in the first sub-step 3051, when the control unit 100 of the separation device 1 forms the peeling layer 211 over the entire length in the X-axis direction of the outer edge portion of the ingot 200 near the second orientation flat 205, the holding unit 10 is moved by the Y-axis moving unit 32 by a predetermined moving distance 26 in the direction in which the condenser 23 of the laser processing unit 20 faces the center of the first surface 201 of the ingot 200 and is moved in the Y-axis direction along the first orientation flat 204 (hereinafter referred to as index feed).

[0079] In Embodiment 1, in the first sub-step 3051, the control unit 100 of the separation device 1 alternately repeats the irradiation of the laser beam 21 while moving the holding unit 10 in the X-axis direction by the X-axis moving unit 31 and the index feed until the peeling layer 211 is formed over the entire area below the first surface 201.

[0080] As a result, as shown in FIGS. 11 and 12, for every indexing feed movement distance of 26, the ingot 200 forms a peeling layer 211 with reduced strength compared to other portions including a modified portion 214 where SiC is separated into Si and C and a crack 215 at a depth corresponding to the thickness 222 of the wafer 220 from the first surface 201. The ingot 200 forms a peeling layer 211 for every indexing feed movement distance over the entire length in the direction parallel to the first orientation flat 204 at a depth corresponding to the thickness 222 of the wafer 220 from the first surface 201.

[0081] The second sub-step 3052 is a step of repeatedly relatively moving the condensing point in the Y-axis direction after relatively moving the condensing point while irradiating the laser beam 21 from one end to the other end of the Facet region 217 in the X-axis direction before or after the first sub-step 3051. In Embodiment 1, in the second sub-step 3052, the control unit 100 of the separation device 1 uses 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 ) of each position 217-1, 217-2, 217-3 ··· 217-N on the outer edge of the Facet region 217 stored in the storage device to adjust the relative position between the ingot 200 and the condenser of the laser processing unit 20. In Embodiment 1, the center between adjacent peeling layers 211 in the Y-axis direction at the outer edge portion closer to the side away from the second orientation flat 205 of the Facet region 217 of the ingot 200 and the condenser 23 are opposed to each other along the Z-axis direction.

[0082] In Embodiment 1, in the second sub-step 3052, the control unit 100 of the separation device 1 relatively moves the holding unit 10 at a predetermined processing feed rate in the X-axis direction, i.e., along the second orientation flat 205, with the X-axis movement unit 31 while irradiating the ingot 200 with the laser beam 21 having a wavelength that is transmissive to SiC from the condenser to form the peeling layer 211 over the entire length of the Facet region 217 in the X-axis direction.

[0083] In Embodiment 1, in the first sub-step 3051, when the control unit 100 of the separation device 1 forms the peeling layer 211 over the entire length in the X-axis direction of the outer edge portion on the side away from the second orientation flat 205 of the Facet region 217 of the ingot 200, the Y-axis moving unit 32 moves the holding unit 10 in the direction in which the condenser of the laser processing unit 20 faces the center of the first surface 201 of the ingot 200 by a predetermined moving distance 26 and moves it in the Y-axis direction along the first orientation flat 204 (hereinafter referred to as index feed).

[0084] In Embodiment 1, in the second sub-step 3052, as shown in FIG. 13, the control unit 100 of the separation device 1 alternately performs the irradiation of the laser beam 21 while moving the holding unit 10 in the X-axis direction by the X-axis moving unit 31 and the index feed until the peeling layer 211 is formed at the center in the Y-axis direction of the peeling layer 211 formed in the first sub-step 3051 over the entire area below the first surface 201 of the Facet region 217. Thus, in Embodiment 1, in Embodiment 1, in the laser processing step 305, the predetermined moving distance 26 (corresponding to the interval) of the index feed in the first sub-step 3051 is made equal to the predetermined moving distance 26 (corresponding to the interval) of the index feed in the second sub-step 3052.

[0085] Thus, in Embodiment 1, in the second sub-step 3052 of the laser processing step 305, by forming the release layer 211 at the center of the release layer 211 formed in the first sub-step 3051 in the Y-axis direction, the ingot 200 is irradiated with the laser beam 21 at different positions in the Y-axis direction in the first sub-step 3051 and the second sub-step 3052. Also, in Embodiment 1, in the laser processing step 305, in the second sub-step 3052, by forming the release layer 211 at the center of the release layer 211 formed in the first sub-step 3051 in the Y-axis direction, the interval between the modified portions 214 adjacent in the Y-axis direction in the Facet region 217 is set to be narrower than the interval between the modified portions 214 adjacent in the Y-axis direction in the non-Facet region 218 outside the Facet region 217.

[0086] Also, in Embodiment 1, in the laser processing step 305, by making the predetermined moving distance 26 for the index feed in the first sub-step 3051 equal to the predetermined moving distance 26 for the index feed in the second sub-step 3052, the condensing point is relatively moved in the index feed direction by the same index amount in the first sub-step 3051 and the second sub-step 3052.

[0087] Also, in Embodiment 1, in the laser processing step 305, the processing conditions such as the output, repetition frequency, and processing feed speed of the laser beam 21 in the first sub-step 3051 and the second sub-step 3052 are made equal, but in the present invention, they may be made different. Also, in the laser processing step 305, the depth of the condensing point of the laser beam 21 in the first sub-step 3051 and the second sub-step 3052 is made equal, but in the present invention, they may be made different. In this case, in the second sub-step 3052, the depth of the condensing point may be made shallower than that in the first sub-step 3051, that is, the position of the condensing point may be changed toward the condenser lens side, and the laser beam 21 may be irradiated.

[0088] (Separation step) FIG. 14 is a perspective view schematically showing the separation step of the separation method shown in FIG. 6. The separation step 306 is a step of separating the ingot 200 from the release layer 211 to the first surface 201 side and the second surface 202 side after performing the laser processing step 305.

[0089] In Embodiment 1, in the separation step 306, the separation device 1 positions the holding unit 10 below the holding plate 71 of the separation unit 70 by the control unit 100 controlling the moving unit 30. In Embodiment 1, in the separation step 306, the separation device 1 causes the control unit 100 to control the separation unit 70 to lower the holding plate 71 and suck and hold the first surface 201 of the ingot 200 on the holding plate 71.

[0090] In Embodiment 1, in the separation step 306, as shown in FIG. 14, the separation device 1 causes the control unit 100 to control the separation unit 70 to apply ultrasonic waves to the holding plate 71 for a predetermined time by the ultrasonic vibration applying means. Then, the ingot 200 breaks starting from the release layer 211. In Embodiment 1, in the separation step 306, the separation device 1 causes the control unit 100 to control the separation unit 70 to raise the holding plate 71 and separate and peel a part, that is, the wafer 220 to be generated, from the ingot 200, that is, separate the ingot 200 to the first surface 201 side and the second surface 202 side.

[0091] Note that the holding step 301, the specific region setting step 304, and the laser processing step 305 of the separation method described above constitute a separation starting point forming method for forming a release layer 211 for separating the ingot 200 having the first surface 201 and the second surface 202 on the back of the first surface 201 to the first surface 201 side and the second surface 202 side inside the ingot 200.

[0092] Generally, since the Facet region 217 has a higher energy absorption rate than the non-Facet region 218, the energy intensity at the condensing point decreases compared to the non-Facet region 218. Therefore, in the Facet region 217, there are fewer cracks 215 extending along the c-plane 209 from the formed modified portion 214 compared to the non-Facet region 218, the extension amount of the crack 215 is also shorter, and there is a risk that the adjacent release layers 211 are not connected by the crack 215, resulting in peeling failure. Thus, in the separation starting point forming method and the separation method according to Embodiment 1, the interval between the modified portions 214 adjacent in the Y-axis direction in the Facet region 217 is set to be narrower than the interval between the modified portions 214 adjacent in the Y-axis direction in the non-Facet region 218 outside the Facet region 217, so that the risk of separation failure in the Facet region 217 can be suppressed.

[0093] As a result, the separation starting point forming method and the separation method according to Embodiment 1 have the effect of suppressing separation failure of the ingot 200.

[0094] (Modification Example 1) The separation starting point forming method and the separation method according to Modification Example 1 of Embodiment 1 will be described with reference to the drawings. FIG. 15 is a plan view schematically showing an ingot after the first sub-step of the laser processing step of the separation starting point forming method and the separation method according to Modification Example 1 of Embodiment 1. FIG. 16 is a plan view schematically showing the path of the laser beam irradiated in the second sub-step of the laser processing step of the separation starting point forming method and the separation method according to Modification Example 1 of Embodiment 1. In addition, the same reference numerals are given to the same parts as in Embodiment 1 in FIGS. 15 and 16, and the description thereof is omitted.

[0095] The separation starting point formation method and separation method according to Modification 1 are the same as those in Embodiment 1, except that in the first sub-step 3051 of the laser processing step 305, as shown in FIG. 15, the peeling layer 211 is formed only in the non-Facet region 218, and in the second sub-step 3052, as shown in FIG. 16, the peeling layer 211 is formed only in the Facet region 217, and the predetermined movement distance 26-1 for index feeding in the second sub-step 3052 is made narrower than the predetermined movement distance 26 for index feeding in the first sub-step 3051.

[0096] In Modification 1, in the first sub-step 3051 of the laser processing step 305, as in Embodiment 1, the control unit 100 of the separation device 1 alternately performs irradiation of the laser beam 21 while moving the holding unit 10 in the X-axis direction by the X-axis moving unit 31 and index feeding, and repeats until the peeling layer 211 is formed over the entire area below the first surface 201. Also, based on 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 ) of each position 217-1, 217-2, 217-3 ··· 217-N of the outer edge of the Facet region 217 stored in the storage device, the irradiation of the laser beam 21 on the Facet region 217 is stopped.

[0097] In Modification 1, in the first sub-step 3051 of the laser processing step 305, as in Embodiment 1, the irradiation of the laser beam 21 while moving the holding unit 10 in the X-axis direction by the X-axis moving unit 31 and index feeding are alternately repeated until the peeling layer 211 is formed over the entire area below the first surface 201 of the Facet region 217. Also, the predetermined movement distance 26-1 for index feeding in the second sub-step 3052 is made narrower than the predetermined movement distance 26 for index feeding in the first sub-step 3051.

[0098] In the separation starting point forming method and the separation method according to Modification 1, by making the predetermined movement distance 26 - 1 for index feed in the second sub-step 3052 narrower than the predetermined movement distance 26 for index feed in the first sub-step 3051, the laser beam 21 is irradiated at different positions in the Y-axis direction in the first sub-step 3051 and the second sub-step 3052 on the ingot 200. Further, in the separation starting point forming method and the separation method according to Modification 1, by making the predetermined movement distance 26 - 1 for index feed in the second sub-step 3052 narrower than the predetermined movement distance 26 for index feed in the first sub-step 3051, the interval between the modified portions 214 adjacent in the Y-axis direction in the Facet region 217 is set to be narrower than the interval between the modified portions 214 adjacent in the Y-axis direction in the non-Facet region 218 outside the Facet region 217.

[0099] In the separation starting point forming method and the separation method according to Modification 1, since the interval between the modified portions 214 adjacent in the Y-axis direction in the Facet region 217 is set to be narrower than the interval between the modified portions 214 adjacent in the Y-axis direction in the non-Facet region 218 outside the Facet region 217, similar to Embodiment 1, it is possible to suppress the risk of separation failure in the Facet region 217, and there is an effect that separation failure of the ingot 200 can be suppressed.

[0100] (Modification 2) The separation starting point forming method and the separation method according to Modification 2 of Embodiment 1 will be described with reference to the drawings. FIG. 17 is a plan view schematically showing the paths of the laser beams irradiated in the first sub-step and the second sub-step of the laser processing step of the separation starting point forming method and the separation method according to Modification 2 of Embodiment 1. In addition, the same reference numerals are given to the same parts as in Embodiment 1, and the description thereof is omitted.

[0101] The separation starting point formation method and separation method according to Modification 2 are the same as those of Embodiment 1, except that, as shown in FIG. 17, in the laser processing step 305, the second sub-step 3052 is carried out during the first sub-step 3051, and the predetermined movement distance 26-2 for the index feed in the second sub-step 3052 is made narrower than the predetermined movement distance 26 for the index feed in the first sub-step 3051.

[0102] In Modification 1, in the laser processing step 305, as in Embodiment 1, the control unit 100 of the separation device 1 alternately performs the irradiation of the laser beam 21 while moving the holding unit 10 in the X-axis direction by the X-axis moving unit 31 and the index feed until the peeling layer 211 is formed over the entire area below the first surface 201. When repeating this, based on 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 ) of each position 217-1, 217-2, 217-3···217-N on the outer edge of the Facet area 217 stored in the storage device, the predetermined movement distance 26-2 for the index feed in the second sub-step 3052 is made narrower than the predetermined movement distance 26 for the index feed in the first sub-step 3051 on the Facet area 217.

[0103] In the separation starting point forming method and the separation method according to Modification 2, by making the predetermined moving distance 26 - 2 for index feeding in the second sub-step 3052 narrower than the predetermined moving distance 26 for index feeding in the first sub-step 3051, the laser beam 21 is irradiated on the ingot 200 at different positions in the Y-axis direction in the first sub-step 3051 and the second sub-step 3052. Further, in the separation starting point forming method and the separation method according to Modification 2, by making the predetermined moving distance 26 - 2 for index feeding in the second sub-step 3052 narrower than the predetermined moving distance 26 for index feeding in the first sub-step 3051, the interval between the modified portions 214 adjacent in the Y-axis direction in the Facet region 217 is set to be narrower than the interval between the modified portions 214 adjacent in the Y-axis direction in the non-Facet region 218 outside the Facet region 217.

[0104] In the separation starting point forming method and the separation method according to Modification 2, since the interval between the modified portions 214 adjacent in the Y-axis direction in the Facet region 217 is set to be narrower than the interval between the modified portions 214 adjacent in the Y-axis direction in the non-Facet region 218 outside the Facet region 217, similar to Embodiment 1, it is possible to suppress the risk of separation failure in the Facet region 217 and achieve the effect of suppressing the separation failure of the ingot 200.

[0105] Note that the present invention is not limited to the above-described embodiments. That is, various modifications can be made and implemented without departing from the gist of the present invention. For example, in Embodiment 1 and Modification 1, in the laser processing step 305, the second sub-step 3052 is performed after the first sub-step 3051. However, in the present invention, the first sub-step 3051 may be performed after the second sub-step 3052. Further, in the present invention, the specific region setting step 304 may be performed before the holding step 301. Also, the present invention is not limited to the workpiece being the above-described ingot 200, and for example, it may be the wafer 220 shown in FIG. 4 separated from the ingot 200.

Explanation of Reference Numerals

[0106] 1 Separation device 10 Holding unit 20 Laser processing unit 21 Laser beam 26 Moving distance (index amount) 26-1, 26-2 Moving distance (index amount) 200 Ingot (workpiece) 201 First surface 202 Second surface 211 Release layer (separation starting point) 214 Modified part 217 Facet area (specific area) 218 Non-Facet area (outside specific area) 220 Wafer (workpiece) 301 Holding step 304 Specific area setting step 305 Laser processing step 306 Separation step 3051 First sub-step 3052 Second sub-step X Processing feed direction Y Index feed direction

Claims

1. A separation starting point forming method for forming a separation starting point inside a workpiece having a first surface and a second surface on the back of the first surface, the separation starting point being formed inside the workpiece, comprising: a holding step of holding the workpiece with a holding unit to expose the first surface; a specific area setting step of setting a specific area on the first surface of the workpiece before or after performing the holding step; after performing the holding step and the specific area setting step, while positioning the condensing point of the laser beam inside the workpiece, irradiating the laser beam toward the first surface and relatively moving the condensing point in the machining feed direction with respect to the workpiece to form a strip-shaped modified portion inside the workpiece, and an index feed of relatively moving the condensing point in the index feed direction orthogonal to the machining feed direction with respect to the workpiece after the machining feed, and repeating the above to form a plurality of modified portions inside the workpiece and form a separation starting point including the plurality of modified portions inside the workpiece, a laser machining step; In the laser machining step, a separation starting point forming method, wherein the interval between adjacent modified portions in the specific area is set to be narrower than the interval between adjacent modified portions outside the specific area.

2. The laser machining step includes: a first sub-step of relatively moving the condensing point while irradiating the laser beam from one end to the other end of the outer peripheral edge of the workpiece in the machining feed direction, and then repeating the relative movement of the condensing point in the index feed direction; before or after the first sub-step, a second sub-step of relatively moving the condensing point while irradiating the laser beam from one end to the other end of the specific area in the machining feed direction, and then repeating the relative movement of the condensing point in the index feed direction; The separation starting point forming method according to claim 1, wherein the laser beam is irradiated at different positions in the index feed direction in the first sub-step and the second sub-step.

3. The separation starting point forming method according to claim 2, wherein in the first sub-step and the second sub-step, the condensing point is relatively moved by the same index amount in the index feed direction.

4. The separation starting point forming method according to any one of claims 1 to 3, wherein in the specific area setting step, the specific area is set based on the optical characteristics of the workpiece.

5. A separation method for separating a workpiece having a first surface and a second surface on the back of the first surface into a first surface side and a second surface side, a holding step of holding the workpiece with a holding unit to expose the first surface, a specific area setting step of setting a specific area on the first surface of the workpiece before or after performing the holding step, after performing the holding step and the specific area setting step, while positioning the condensing point of the laser beam inside the workpiece, irradiating the laser beam toward the first surface and relatively moving the condensing point in the processing feed direction with respect to the workpiece to form a strip-shaped modified portion inside the workpiece, and an index feed of relatively moving the condensing point in the index feed direction orthogonal to the processing feed direction with respect to the workpiece after the processing feed, and repeating these to form a plurality of modified portions inside the workpiece and form a separation starting point including the plurality of modified portions inside the workpiece, a laser processing step, after performing the laser processing step, a separation step of separating the workpiece into a first surface side and a second surface side from the separation starting point, and in the laser processing step, a separation method in which the interval between adjacent modified portions in the specific area is set to be narrower than the interval between adjacent modified portions outside the specific area.

Images