Alignment Method

Abstract

To provide an alignment method by which alignment can be efficiently and accurately executed even if an angle of an orientation flat is largely deviated.SOLUTION: An alignment method for aligning a first orientation flat 105 formed on a workpiece 100 with a direction parallel to a desired direction, includes: a straight line detection step of picking up an image of the first orientation flat 105 by using an imaging unit 30 and detecting a straight line area in a photographed image; a first alignment step of calculating a deviation angle between the desired direction and an extension direction of the straight line area detected in the straight line detection step, and locating the extension direction of the straight line area to be parallel to the desired direction based on the deviation angle; and a second alignment step of picking up an image of the first orientation flat 105 at a first position and a second position separated along the desired direction, and locating a line connecting the first orientation flat 105 at the first position and the first orientation flat 105 at the second position to be parallel to the desired direction.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an alignment method. [Background technology]

[0002] As a method for forming a wafer from an ingot, a method has been proposed in which a focused laser beam is irradiated inside the ingot to form a peeling layer, and the wafer is separated from the ingot using this peeling layer as a starting point (see, for example, Patent Document 1).

[0003] In Patent Document 1, the direction of movement of the focal point of the laser beam is set perpendicular to the direction in which the off-angle is formed, i.e., parallel to the second orientation flat. This allows the cracks that propagate along the c-plane from both sides of the release layer to extend very long, thereby enabling a large index amount and improving productivity. Prior to forming the release layer, alignment is performed to align the direction of movement of the focal point with the second orientation flat. This alignment is generally performed by pattern matching (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-111143 [Patent Document 2] Japanese Patent Application Publication No. 60-244803 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned cases, alignment is performed by pre-registering (teaching) the orientation flat as a key pattern and then detecting the orientation flat by capturing an image of the wafer surface using an imaging device such as a microscope. However, if the ingot rotates during transport due to vibration or other factors, the orientation flat angle can shift significantly, making alignment impossible and requiring the operator to reset the ingot. Furthermore, the teaching process to register the orientation flat as a key pattern is performed by the operator, which is time-consuming and prone to human error, so improvements were needed.

[0006] The present invention has been made in consideration of these problems, and its object is to provide an alignment method that can perform alignment efficiently and with high precision even when the orientation flat angle is significantly misaligned. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the alignment method of the present invention aligns an orientation flat formed on a workpiece in a direction parallel to a desired direction, and is characterized by the following steps: a positioning step of positioning an imaging unit that images the workpiece at a position where the orientation flat can be imaged; a line detection step of imaging the orientation flat with the imaging unit and detecting a straight line region in the captured image; a first alignment step of calculating the angle of deviation between the extension direction of the straight line region detected in the line detection step and the desired direction, and positioning the straight line region so that its extension direction is parallel to the desired direction based on the angle of deviation; and a second alignment step of, after performing the first alignment step, imaging the orientation flat at first and second positions spaced apart along the desired direction, and positioning the orientation flat so that a line connecting the orientation flat at the first position and the orientation flat at the second position is parallel to the desired direction.

[0008] The second alignment step may involve detecting an orientation flat image at the first position and the second position by pattern matching that has the same orientation flat ratio as the reference orientation flat image, calculating the angle of deviation between the orientation flat and the desired direction based on the XY coordinate position of the orientation flat image detected at the first position and the XY coordinate position of the orientation flat image detected at the second position, and positioning the orientation flat so that it is parallel to the desired direction.

[0009] An image of the orientation flat after alignment in the first alignment step may be used as the reference orientation flat image.

[0010] A pseudo orientation flat image generated in advance may be used as the reference orientation flat image. [Effects of the Invention]

[0011] The present invention allows efficient and accurate alignment even when the orientation flat angle is significantly misaligned. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a laser processing apparatus that performs an alignment method according to an embodiment. [Figure 2] FIG. 2 is a top view showing an example of a workpiece to be aligned using the alignment method according to the embodiment. [Figure 3] FIG. 3 is a flowchart showing the processing procedure of the alignment method according to the embodiment. [Figure 4] FIG. 4 is a perspective view illustrating the positioning step of FIG. [Figure 5] FIG. 5 is a top view illustrating the positioning step of FIG. [Figure 6] FIG. 6 is a diagram showing an example of a captured image captured in the line detection step of FIG. [Figure 7]FIG. 7 is a diagram showing an example of a captured image captured after the first alignment step of FIG. 3 is performed. [Figure 8] FIG. 8 is a top view illustrating the second alignment step of FIG. [Figure 9] FIG. 9 is a top view illustrating the second alignment step of FIG. [Figure 10] FIG. 10 is a diagram illustrating the second alignment step of FIG. [Figure 11] FIG. 11 is a diagram showing an example of an orientation flat image serving as a reference used in the second positioning step of the alignment method according to the modified embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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.

[0014] [Embodiment] An alignment method according to an 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 a laser processing apparatus 1 that implements the alignment method according to the embodiment. FIG. 2 is a top view showing an example of a workpiece 100 that is the alignment target for implementing the alignment method according to the embodiment. As shown in FIG. 1, the laser processing apparatus 1 that implements the alignment method according to the embodiment includes a holding table 10, a laser beam irradiation unit 20, an imaging unit 30, an X-axis direction moving unit 41, a Y-axis direction moving unit 42, a Z-axis direction moving unit 43, a display unit 50, an input unit 60, and a control unit 70.

[0015] In the embodiment, the workpiece 100, which is the alignment target for performing the alignment method of the embodiment, is a single crystal ingot made of, for example, silicon carbide (SiC) or gallium nitride (gallium nitride, GaN) and formed in a cylindrical shape overall.

[0016] As shown in FIGS. 1 and 2 , workpiece 100 has first surface 101, which is a generally circular end face, second surface 102, which is generally circular and located on the reverse side of first surface 101, and peripheral surface 104, which is continuous with the outer edges of first surface 101 and second surface 102. Workpiece 100 also has first orientation flat 105, which indicates a crystal orientation, and second orientation flat 106, which is perpendicular to first orientation flat 105, formed on peripheral surface 104. "Orientation flat" is an abbreviation for "orientation flat." In this embodiment, first orientation flat 105 has a longer linear region than second orientation flat 106.

[0017] Furthermore, workpiece 100 has a c-axis that is tilted at an off-angle relative to the perpendicular to first surface 101 in a direction toward second orientation flat 106, and a c-plane that is perpendicular to the c-axis. The c-plane is tilted at the same angle as the off-angle relative to first surface 101 of workpiece 100. The off-angle can be freely set within a range of, for example, 1° to 6°. The direction in which the off-angle is formed is perpendicular to the extension direction of second orientation flat 106 and parallel to first orientation flat 105.

[0018] By irradiating the workpiece 100 with a transparent laser beam, the direction of movement of the focal point of the laser beam is set perpendicular to the direction in which the off-angle is formed, i.e., parallel to the second orientation flat 106, and the workpiece 100 is modified inside the workpiece 100, forming very long cracks that propagate along the c-plane from both sides of the modified region, and the wafer is separated from the peel layer containing the modified region and cracks. The modified region is a region whose density, refractive index, mechanical strength, or other physical properties are different from those of the surrounding area.

[0019] The holding table 10 includes a disk-shaped frame body with a recess formed therein and a disk-shaped suction portion fitted into the recess. The suction portion of the holding table 10 is formed of a porous ceramic or the like with numerous porous holes and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). As shown in FIG. 2, the upper surface of the suction portion of the holding table 10 is a holding surface 11 on which a workpiece 100 is placed and which suction-holds the placed workpiece 100 by negative pressure introduced from the vacuum suction source. In this embodiment, the workpiece 100 is placed with its first surface 101 facing upward, and the holding surface 11 suction-holds the placed workpiece 100 from its second surface 102. The holding surface 11 and the upper surface of the frame body of the holding table 10 are arranged on the same plane and are parallel to the horizontal XY plane.

[0020] The holding table 10 is provided so as to be movable in the X-axis direction parallel to the horizontal direction by an X-axis movement unit 41, and so as to be movable in the Y-axis direction parallel to the horizontal direction and perpendicular to the X-axis direction by a Y-axis movement unit 42. The holding table 10 is moved along the X-axis and Y-axis by the X-axis movement unit 41 and the Y-axis movement unit 42, respectively, to move the workpiece 100 held on the holding table 10 in the X-axis and Y-axis directions relative to the focal point formed by the laser beam irradiation unit 20 and the imaging unit 30, respectively. The holding table 10 is provided so as to be rotatable about the Z-axis parallel to the vertical direction and perpendicular to the XY plane by a rotary drive source (not shown).

[0021] In this embodiment, the laser beam irradiation unit 20 irradiates a laser beam having a wavelength that is transparent to the workpiece 100 from the first surface 101 side toward the inside of the workpiece 100 held on the holding table 10, and the laser beam forms a peeling layer inside the workpiece 100. The laser beam irradiation unit 20 is configured to include, for example, a laser beam oscillator (not shown) that generates a laser beam, and a condenser that collects the laser beam generated by the laser beam oscillator and irradiates it toward the inside of the workpiece 100.

[0022] The condenser included in the laser beam irradiation unit 20 is provided so as to be movable in the Z-axis direction by the Z-axis direction movement unit 43. The condenser included in the laser beam irradiation unit 20 is moved along the Z-axis direction by the Z-axis direction movement unit 43, thereby moving the focal point of the laser beam in the Z-axis direction relative to the workpiece 100 held on the holding table 10.

[0023] The imaging unit 30 includes an imaging element that captures images of the first surface 101, outer edge, first orientation flat 105, etc. of the workpiece 100 held on the holding table 10. The imaging element is, for example, a charge-coupled device (CCD) imaging element or a complementary metal-oxide semiconductor (CMOS) imaging element. In this embodiment, the imaging unit 30 is disposed adjacent to the condenser included in the laser beam irradiation unit 20 so as to move integrally with the condenser included in the laser beam irradiation unit 20. A reference line (center line) 31 (see FIGS. 6 and 7) that extends along the X-axis direction and divides the imaging area in half in the Y-axis direction is provided within the imaging unit 30.

[0024] Imaging unit 30 captures images of three spaced apart points on the outer edge of first surface 101 of workpiece 100, which is held on holding table 10 and before the formation of the release layer, excluding the locations where first orientation flat 105 and second orientation flat 106 are formed, and performs geometric calculation processing based on the coordinates of the three points to obtain an image for performing edge alignment, which determines the accurate center coordinates and diameter when first surface 101 of workpiece 100 is considered to be circular, and outputs the obtained image to control unit 70. In this embodiment, the image for performing edge alignment is captured by first surface 101 of workpiece 100, with the outer edge as the boundary, with the inner region of the outer periphery reflecting the illumination of imaging unit 30 at a higher brightness than the outer edge, and the outer region of the outer periphery not reflecting the illumination of imaging unit 30 at a lower brightness.

[0025] After edge alignment is performed, the imaging unit 30 is positioned toward the center of the first surface 101 of the workpiece 100 determined by the edge alignment, performs autofocus to automatically focus the image on the center of the first surface 101 of the workpiece 100, and automatically performs automatic light intensity adjustment to automatically adjust the light intensity of the illumination of the imaging unit 30 so that the center of the first surface 101 of the workpiece 100 can be imaged most clearly.

[0026] Imaging unit 30 is also positioned at first orientation flat 105 of workpiece 100, images first orientation flat 105, and obtains an image for performing orientation flat alignment (orientation flat alignment) using first orientation flat 105 to align the movement direction of the focal point of the laser beam with second orientation flat 106. The obtained image is output to control unit 70. In the alignment method according to the embodiment, the orientation flat alignment process includes a first alignment step 1003 (see FIG. 3 ) and a second alignment step 1004 (see FIG. 3 ). In this embodiment, the image for performing orientation flat alignment is captured by first surface 101 of workpiece 100, with first orientation flat 105 as the boundary, with the region inside first orientation flat 105 reflecting illumination from imaging unit 30 at a higher brightness and the region outside first orientation flat 105 not reflecting illumination from imaging unit 30 at a lower brightness. In this embodiment, the images used to perform orientation flat alignment are, for example, captured images 201 and 202 and orientation flat image 203 (see FIGS. 6 and 7), which will be described later. However, the present invention is not limited to this. Imaging unit 30 may be positioned at second orientation flat 106 of workpiece 100, capture an image of second orientation flat 106, obtain an image for performing orientation flat alignment using second orientation flat 106, and output the obtained image to control unit 70.

[0027] The X-axis direction moving unit 41 and the Y-axis direction moving unit 42 move the holding table 10 along the X-axis direction and the Y-axis direction, respectively, relative to the condenser included in the laser beam irradiation unit 20. The Z-axis direction moving unit 43 moves the condenser included in the laser beam irradiation unit 20 along the Z-axis direction relative to the holding table 10. The X-axis direction moving unit 41, the Y-axis direction moving unit 42, and the Z-axis direction moving unit 43 are each configured to include, for example, a well-known ball screw provided to be rotatable about the X-axis, Y-axis, and Z-axis axes, a well-known pulse motor that rotates the ball screw about the axis, and a well-known guide rail that supports the holding table 10 or the condenser included in the laser beam irradiation unit 20 so as to be movably in the X-axis, Y-axis, or Z-axis direction.

[0028] The X-axis direction moving unit 41, the Y-axis direction moving unit 42, and the Z-axis direction moving unit 43 each include an encoder that reads the rotational position of the pulse motor, and detects the relative positions of the holding table 10 and the condenser included in the laser beam irradiation unit 20 in the X-axis direction, the Y-axis direction, and the Z-axis direction based on the rotational position of the pulse motor read by the encoder, and outputs the detected relative positions to the control unit 70. Note that the X-axis direction moving unit 41, the Y-axis direction moving unit 42, and the Z-axis direction moving unit 43 are not limited to a configuration in which the relative position of the holding table 10 and the condenser included in the laser beam irradiation unit 20 is detected by an encoder, and may each be configured by a linear scale parallel to the X-axis direction, the Y-axis direction, and the Z-axis direction, and a read head that is movable in the X-axis direction, the Y-axis direction, and the Z-axis direction by the X-axis direction moving unit 41, the Y-axis direction moving unit 42, and the Z-axis direction moving unit 43, respectively, and that reads the graduations of the linear scale.

[0029] The display unit 50 is provided on a cover (not shown) of the laser processing apparatus 1 with its display surface facing outward, and displays screens for setting the laser beam irradiation conditions of the laser processing apparatus 1, as well as screens showing the results of edge alignment, autofocus, automatic light intensity adjustment, orientation flat alignment, and processing for forming a peeling layer, so that the operator can see them. The display unit 50 is configured with a liquid crystal display device or the like. The display unit 50 is provided with an input unit 60 that the operator uses to input command information regarding various operations of the laser processing apparatus 1, laser beam irradiation conditions, image display, etc. The input unit 60 provided on the display unit 50 is configured with at least one of a touch panel provided on the display unit 50 and a keyboard or the like.

[0030] The control unit 70 controls the operation of each component of the laser processing apparatus 1, causing the laser processing apparatus 1 to perform edge alignment, autofocus, automatic light intensity adjustment, orientation flat alignment, and laser beam irradiation to form a peeling layer. The control unit 70 performs image processing on images for edge alignment and orientation flat alignment. In this image processing, the control unit 70 calculates various XY coordinates using an apparatus Cartesian coordinate system (XY coordinate system) with the center of the holding table 10 as its origin and an apparatus Cartesian coordinate system (XY coordinate system) with the center of each image as its origin. As shown in FIG. 1, the control unit 70 includes a memory unit 71. The memory unit 71 stores information such as the diameter and thickness of the workpiece 100, the positions of the first orientation flat 105 and the second orientation flat 106, the lengths of their linear regions, and images for edge alignment and orientation flat alignment.

[0031] In the first embodiment, the control unit 70 includes a computer system. The computer system included in the control unit 70 includes an arithmetic processing device having a microprocessor such as a CPU (Central Processing Unit), a storage device having memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and an input / output interface device. The arithmetic processing device of the control unit 70 performs arithmetic processing in accordance with a computer program stored in the storage device of the control unit 70, and outputs control signals for controlling the laser processing apparatus 1 to each component of the laser processing apparatus 1 via the input / output interface device of the control unit 70. In this embodiment, the function of the storage unit 71 is realized by the storage device of the control unit 70.

[0032] Next, this specification will explain an alignment method according to an embodiment with reference to the drawings. FIG. 3 is a flowchart showing the processing steps of the alignment method according to the embodiment. The alignment method according to the embodiment is an example of the operation processing of laser processing apparatus 1, and is a method for aligning first orientation flat 105 or second orientation flat 106 formed on workpiece 100 in a direction parallel to a desired direction. As shown in FIG. 3, the alignment method according to the embodiment includes a positioning step 1001, a straight line detection step 1002, a first alignment step 1003, and a second alignment step 1004.

[0033] In this embodiment, the alignment target is first Orientation Flat 105, which is formed parallel to the direction in which the off-angle is formed, and the desired alignment direction is a direction parallel to the X-axis direction, which is perpendicular to the Y-axis direction, along which the focal point of the laser beam moves. However, this is not limited to this. The alignment target may be second Orientation Flat 106, and the desired alignment direction may be the Y-axis direction. Alternatively, the desired alignment direction may be changed as appropriate depending on the direction of movement of the focal point of the laser beam or the alignment target. The alignment method according to this embodiment uses first Orientation Flat 105, which has a longer linear region than second Orientation Flat 106, and therefore can further improve the accuracy of Orientation Flat alignment in first alignment step 1003 and second alignment step 1004, which is preferable.

[0034] In the alignment method according to the embodiment, before performing positioning step 1001, control unit 70 first transports workpiece 100 onto holding table 10 using a transport unit (not shown) or the like, and holds workpiece 100 on holding table 10. Next, control unit 70 acquires images by imaging unit 30 of three spaced apart points on the outer edge of first surface 101 of workpiece 100 held on holding table 10, excluding the locations where first orientation flat 105 and second orientation flat 106 are formed, and performs edge alignment based on these images. After performing edge alignment, control unit 70 causes imaging unit 30 to perform autofocus and automatic light intensity adjustment.

[0035] In edge alignment, the control unit 70 detects the XY coordinates of one boundary point between high and low brightness in each image based on a total of three images of the outer edge of the first surface 101 of the workpiece 100 for performing edge alignment. Then, the control unit 70 performs geometric calculation processing based on the coordinates of the three points to determine the accurate center coordinates (XY coordinates) and diameter when the first surface 101 of the workpiece 100 is considered to be circular.

[0036] 4 and 5 are perspective and top views, respectively, illustrating positioning step 1001 of Fig. 3. Positioning step 1001 is a step of positioning imaging unit 30 at a position where it can capture an image of first orientation flat 105, as shown in Figs.

[0037] In positioning step 1001, control unit 70 first estimates the coordinates of the center of first orientation flat 105 based on the center coordinates and diameter of first surface 101 of workpiece 100 determined in the previous edge alignment, and on information about the position of first orientation flat 105 and the length of its linear region pre-stored in memory 71. In positioning step 1001, control unit 70 then moves holding table 10 along the X-axis and Y-axis directions using X-axis movement unit 41 and Y-axis movement unit 42, respectively, based on the estimated coordinates of the center of first orientation flat 105, thereby moving imaging unit 30 relatively to the center of first orientation flat 105.

[0038] Figure 6 is a diagram showing an example of captured image 201 captured in line detection step 1002 of Figure 3. Line detection step 1002 is a step in which first orientation flat 105 is imaged by imaging unit 30 positioned in positioning step 1001 to obtain captured image 201 shown in Figure 6, and linear regions are detected within captured image 201. In line detection step 1002, control unit 70 detects the X and Y coordinates of multiple points within captured image 201 that are boundaries between high and low brightness regions that indicate first orientation flat 105, and then performs arithmetic processing such as a Hough transform on the X and Y coordinates of the multiple points within captured image 201 to detect lines within captured image 201 that correspond to first orientation flat 105.

[0039] The first alignment step 1003 is a step of calculating the deviation angle θ1 (see Figure 6) between the extension direction of the straight line region detected in the straight line detection step 1002 and the desired direction, and positioning the straight line region so that its extension direction is parallel to the desired direction based on the deviation angle θ1.

[0040] 6 , in this embodiment, the extension direction of the straight line region detected in straight line detection step 1002 corresponds to the extension direction of first orientation flat 105 in captured image 201, and the desired direction is set to the X-axis direction as described above, which is the extension direction of reference line 31 in captured image 201. Therefore, in first alignment step 1003, control unit 70 calculates, as deviation angle θ1, the angle between the straight line corresponding to first orientation flat 105 and reference line 31 based on the equation of the straight line corresponding to first orientation flat 105 detected in straight line detection step 1002 and the equation of the straight line of reference line 31.

[0041] In the first alignment step 1003, the control unit 70 rotates the holding table 10 by an angle -θ1 using the rotary drive source by an amount equal to the calculated deviation angle θ1 in a direction that cancels out the calculated deviation angle θ1, thereby rotating the workpiece 100 by an angle -θ1 and rotating the extension direction of the first orientation flat 105 by an angle -θ1, thereby positioning the extension direction of the first orientation flat 105 so that it is parallel to the extension direction of the reference line 31.

[0042] Therefore, in first alignment step 1003, alignment can be performed to make the extension direction of first orientation flat 105 parallel to the desired direction within the detection limit of deviation angle θ1 when deviation angle θ1 is calculated using straight lines detected within the range of one captured image 201. First alignment step 1003 is a coarser alignment step than second alignment step 1004, which will be described later.

[0043] In first alignment step 1003, control unit 70 may find that first orientation flat 105 is not found within the imaging area of ​​imaging unit 30 due to alignment to make the extension direction of first orientation flat 105 parallel to the extension direction of reference line 31. In such a case, in first alignment step 1003, control unit 70 further moves holding table 10 along the Y-axis using Y-axis movement unit 42, thereby relatively moving imaging unit 30 along the Y-axis, and adjusting first orientation flat 105 so that it is within the imaging area of ​​imaging unit 30.

[0044] Figure 7 is a diagram showing an example of captured image 202 captured after first alignment step 1003 in Figure 3. After alignment is performed in first alignment step 1003, control unit 70 captures an image of first orientation flat 105 using imaging unit 30, thereby obtaining captured image 202 in which the extension direction of first orientation flat 105 is parallel to the extension direction of reference line 31, as shown in Figure 7.

[0045] 8 and 9 are top views illustrating the second alignment step 1004 of FIG. 3. In the second alignment step 1004, after the first alignment step 1003, images of the first orientation flat 105 are taken at first position 105-1 and second position 105-2, which are spaced apart along a desired direction (the X-axis direction), and the first orientation flat 105 is positioned so that a line 105-3 connecting the first orientation flat 105 at first position 105-1 and the first orientation flat 105 at second position 105-2 is parallel to the desired direction, as shown in FIGS. In this embodiment, the desired direction is set to the X-axis direction.

[0046] In the second alignment step 1004, the control unit 70 first moves the imaging unit 30 to a first position 105-1 using the X-axis movement unit 41 and the Y-axis movement unit 42, as shown in FIG. 8. At first position 105-1, the control unit 70 captures images of the first Orientation Flat 105 while shifting the imaging unit 30 relatively along the Y-axis by small increments using the Y-axis movement unit 42, thereby acquiring multiple first Orientation Flat images. The control unit 70 then performs pattern matching between the reference Orientation Flat image 203 (see FIG. 7) and the multiple first Orientation Flat images to find a first Orientation Flat image with the same Orientation Flat ratio as the reference Orientation Flat image 203. In this embodiment, the control unit 70 uses the captured image 202, captured after the first alignment step 1003, as the reference Orientation Flat image 203. The orientation flat ratio refers to the ratio of the area of ​​the region inside first orientation flat 105 to the area of ​​the region outside first orientation flat 105 in the orientation flat image, i.e., the ratio of the area of ​​the high-intensity region representing the region inside first orientation flat 105 to the area of ​​the low-intensity region representing the region outside first orientation flat 105. As shown in Figure 9, control unit 70 also acquires multiple second orientation flat images at second position 105-2 in the same manner as at first position 105-1, and uses pattern matching to detect second orientation flat images with the same orientation flat ratio as reference orientation flat image 203.

[0047] FIG. 10 is a diagram illustrating the second alignment step 1004 of FIG. 3. In the second alignment step 1004, the control unit 70 next determines the XY coordinate position of the first Orientation Flat image detected at the first position 105-1 ((X1, Y1) in FIG. 10) and the XY coordinate position of the second Orientation Flat image detected at the second position 105-2 ((X2, Y2) in FIG. 10), as shown in FIG. 10. The control unit 70 determines the XY coordinate position of each Orientation Flat image based on the XY coordinates of the position of the imaging unit 30 when the Orientation Flat image was captured. The control unit 70 then calculates the equation of the line 105-3 connecting the first Orientation Flat 105 at the first position 105-1 and the first Orientation Flat 105 at the second position 105-2 based on the XY coordinate position of the first Orientation Flat image detected at the first position 105-1 and the XY coordinate position of the second Orientation Flat image detected at the second position 105-2. Based on the equation of straight line 105-3 and the equation of the straight line of reference line 31, control unit 70 calculates the angle between straight line 105-3 corresponding to first orientation flat 105 and reference line 31 as deviation angle θ2.

[0048] In the second alignment step 1004, the control unit 70 then rotates the holding table 10 by the rotary drive source by an amount equal to the calculated deviation angle θ2 in a direction that cancels out the calculated deviation angle θ2, thereby rotating the workpiece 100 by an angle -θ2 and rotating the extension direction of the first orientation flat 105 by an angle -θ2, thereby positioning the extension direction of the first orientation flat 105 so that it is parallel to the extension direction of the reference line 31.

[0049] Therefore, in the second alignment step 1004, alignment can be performed to make the extension direction of first orientation flat 105 parallel to the desired direction (X-axis direction) within the detection limit of deviation angle θ2 when deviation angle θ2 is calculated using line 105-3 connecting first orientation flat 105 at first position 105-1 and first orientation flat 105 at second position 105-2, which are spaced apart along the desired direction (X-axis). Because the detection limit of deviation angle θ2 in second alignment step 1004 is smaller than the detection limit of deviation angle θ1 in first alignment step 1003, second alignment step 1004 is a more detailed alignment step than first alignment step 1003.

[0050] In the alignment method according to the embodiment, first orientation flat 105 is aligned in a direction parallel to the X-axis direction over two stages, thereby precisely aligning the movement direction of the focal point of the laser beam irradiated to form the release layer in a direction parallel to the Y-axis direction. Then, by rotating holding table 10 by 90 degrees and rotating workpiece 100 by 90 degrees, the movement direction of the focal point of the laser beam irradiated to form the release layer is aligned in a direction parallel to the X-axis direction. Then, laser beam irradiation unit 20 irradiates the interior of workpiece 100 with a laser beam, thereby suitably forming the release layer.

[0051] The alignment method according to the embodiment, configured as described above, performs coarse alignment using line detection without pattern matching in the first alignment step 1003, and then performs detailed alignment using pattern matching at two spaced positions in the second alignment step 1004. Therefore, even if the ingot workpiece 100 rotates during transport due to vibration or other factors, causing the angle (extension direction) of the first orientation flat 105 to shift significantly with respect to the X-axis, the risk of alignment being unable to be performed due to pattern matching being disabled due to a large deviation in the first orientation flat 105 is reduced. This eliminates the need for an operator to reposition the workpiece 100, as in the conventional method. Therefore, the alignment method according to the embodiment achieves the advantageous effect of efficiently and accurately performing alignment even when the angle (extension direction) of the first orientation flat 105 shifts significantly. This contributes to reducing the number of alignment steps and preventing human error by the operator.

[0052] In the second alignment step 1004, the alignment method according to the embodiment uses pattern matching to detect, at first position 105-1 and second position 105-2, an Orientation Flat image with the same Orientation Flat ratio as that of reference Orientation Flat image 203, and calculates the angle (extension direction) of first Orientation Flat 105 based on the XY coordinate position of the first Orientation Flat image detected at first position 105-1 and the XY coordinate position of the second Orientation Flat image detected at second position 105-2. Therefore, the alignment method according to the embodiment can accurately determine the Y-axis position of each Orientation Flat image by pattern matching using the Orientation Flat ratio, thereby accurately calculating the angle (extension direction) of first Orientation Flat 105 and achieving more accurate alignment.

[0053] Furthermore, the alignment method according to the embodiment performs pattern matching using the captured image 202 of the first orientation flat 105 acquired during straight line detection for rough alignment as the orientation flat image 203 that serves as the reference for detailed alignment, eliminating the need to pre-register (teach) the orientation flat pattern as in the conventional method.

[0054] [Modification] An alignment method according to a modified embodiment will be described with reference to the drawings. Figure 11 shows an example of an orientation flat image 204 that serves as a reference for use in the second alignment step 1004 of the alignment method according to the modified embodiment. In Figure 11, the same parts as those in the embodiment are designated by the same reference numerals, and their description will be omitted.

[0055] In the alignment method according to the modified example, the reference orientation flat image 203 used in the second alignment step 1004 in the embodiment is replaced with a reference orientation flat image 204 shown in Fig. 11. As shown in Fig. 11, reference orientation flat image 204 is a pattern image that has been artificially generated in advance and stored in memory unit 71. With pseudo first orientation flat 115 superimposed on reference line 31 as the boundary, pseudo first surface 111 of pseudo workpiece 110 has a high brightness in the region inside pseudo first orientation flat 115, and a low brightness in the region outside pseudo first orientation flat 115.

[0056] Even though the alignment method of the modified example uses such a reference orientation flat image 204, it is possible to perform pattern matching between the orientation flat image 204 and multiple first orientation flat images and second orientation flat images, just as in the embodiment, and since it is not necessary to pre-register (teach) the orientation flat pattern as in the conventional method, it achieves the same effects as embodiment 1.

[0057] 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. [Explanation of symbols]

[0058] 1. Laser processing equipment 30 Imaging unit 31 Reference Line 70 Control Unit 71 Memory section 100 Workpiece 105 First Orientation Flat 105-1 First Position 105-2 Second Position 106 Second Orientation Flat 201,202 Captured images 203,204 Orientation Flat Image θ1,θ2 deviation angle

Claims

1. An alignment method for aligning an orientation flat formed on a workpiece in a direction parallel to a desired direction, comprising: a positioning step of positioning an imaging unit that images the workpiece at a position where the imaging unit can image the orientation flat; a straight line detection step of capturing an image of the orientation flat with the imaging unit and detecting a straight line region within the captured image; a first alignment step of calculating a deviation angle between the extension direction of the straight line region detected in the straight line detection step and the desired direction, and positioning the straight line region so that the extension direction of the straight line region is parallel to the desired direction based on the deviation angle; a second alignment step, after the first alignment step, of capturing images of the orientation flat at a first position and a second position spaced apart along the desired direction, and positioning the orientation flat so that a line connecting the orientation flat at the first position and the orientation flat at the second position is parallel to the desired direction; An alignment method comprising:

2. 2. The alignment method of claim 1, wherein the second alignment step involves detecting an orientation flat image at the first position and the second position by pattern matching that has the same orientation flat ratio as that of a reference orientation flat image, calculating the angle of deviation between the orientation flat and the desired direction based on the XY coordinate position of the orientation flat image detected at the first position and the XY coordinate position of the orientation flat image detected at the second position, and positioning the orientation flat so that it is parallel to the desired direction.

3. 3. The alignment method according to claim 2, wherein an image of the orientation flat after alignment in the first alignment step is used as the reference orientation flat image.

4. 3. The alignment method according to claim 2, wherein a pseudo-orientation flat image generated in advance is used as the reference orientation flat image.

Images