Workpiece processing method

Abstract

To reduce the number and size of chipping when a chamfering part is removed, and to suppress film peeling on a surface of a workpiece.SOLUTION: Provided is a workpiece processing method including a first cutting step and a second cutting step. In the first cutting step, an outer peripheral part of a second surface of a workpiece is cut into by a first cutting blade mounted on a first rotation shaft arranged so as not to cross with an extension line of a rotation center of a first table rotation shaft of a first holding table arranged so as to be orthogonal to a first holding surface on an extension line of a rotation center of the first rotation shaft, the first holding table is rotated, and a first step part having a curved surface is formed in an outer peripheral part of the workpiece. In the second cutting step, the curved surface is cut into by a second cutting blade mounted on a second rotation shaft arranged so as to cross with an extension line of a rotation center of a second table rotation shaft of a second holding table on an extension line of a rotation center of the second rotation shaft, such that the second cutting blade does not contact with the most inner periphery of the curved surface, and the second holding table is rotated, and a second step part is formed in an outer peripheral part of the workpiece.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for processing a workpiece having a plate shape and chamfered portions on the outer peripheral portions of both surfaces.

Background Art

[0002] On the outer peripheral portions of the front and back surfaces of a workpiece having a disk-shaped semiconductor wafer formed of a semiconductor material such as silicon, chamfered portions (also referred to as bevel portions) are usually formed. Therefore, when the thickness of the workpiece is made, for example, half or less of the thickness before grinding by grinding the back surface side of the workpiece, a so-called knife edge (also referred to as a sharp edge) is formed on the outer peripheral portion.

[0003] When a knife edge is formed on the outer peripheral portion, cracks, chips, etc. are likely to occur on the outer peripheral portion during conveyance of the workpiece after grinding. Therefore, in order to prevent this, before grinding the workpiece, a processing method called edge trimming for removing the chamfered portion on the front surface side of the workpiece using a cutting device has been proposed (see, for example, Patent Document 1).

[0004] When performing edge trimming, usually, first, a cutting blade having a thin annular cutting edge is attached to the tip of the spindle of the cutting device, and the workpiece is sucked and held by a chuck table. At this time, the workpiece is sucked and held on the chuck table so that the rotation center of the chuck table and the radial center of the workpiece substantially coincide.

[0005] Then, with the cutting blade and the chuck table arranged such that the extension line of the rotation center of the cutting blade is orthogonal to the extension line of the rotation center of the chuck table, the cutting blade is cut into the outer peripheral portion of the front surface of the workpiece.

[0006] The cutting blade has an annular cutting edge. Each cutting edge is annular and includes one surface and the other surface located on opposite sides in the thickness direction of the cutting blade, and an outer peripheral side surface connecting the outer peripheral portions of the one surface and the other surface.

[0007] After cutting the cutting blade into the outer peripheral part of the surface of the workpiece, the chuck table is slowly rotated while keeping the spatial position of the cutting blade rotating at high speed substantially fixed. Therefore, during cutting, the workpiece comes into contact not only with the outer peripheral side surface of the annular cutting edge but also with one surface of the annular cutting edge.

[0008] In this way, in addition to the outer peripheral side surface of the cutting edge that is planned to cut the workpiece, the workpiece also comes into contact with one surface of the cutting edge, resulting in problems such as (i) the occurrence of chipping and (ii) the peeling of thin films such as oxide films formed on the surface at the outer peripheral part of the surface of the workpiece after cutting.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] The present invention has been made in view of such problems, and aims to reduce the number and size of chipping and suppress film peeling on the surface of the workpiece when removing the chamfered part at the outer peripheral part of the surface of the workpiece.

Means for Solving the Problems

[0011] According to one aspect of the present invention, there is provided a method for processing a workpiece having a plate shape and chamfered portions on the outer circumferences of both sides, comprising: in the thickness direction of the workpiece whose first surface is held by the first holding surface of the first holding table, a first rotating shaft disposed along the first holding surface and located on the opposite side of the first surface and exposed at the outer circumference of the second surface; the tip of the first rotating shaft is arranged so as not to intersect the extension line of the rotation center of the first table rotating shaft of the first holding table which is arranged so as to be orthogonal to the first holding surface on the extension line of the rotation center of the first rotating shaft; a first cutting blade mounted on the tip of the first rotating shaft is cut into the workpiece, and the first holding table is rotated around the first table rotating shaft, thereby forming a first stepped portion having a curved surface that is recessed from the second surface toward the first surface as it advances outward from the center of the second surface at the outer circumference of the workpiece in a first cutting step; after the first cutting step, a second rotating shaft disposed along the second holding surface of the second holding table that holds the first surface of the workpiece; the tip of the second rotating shaft is arranged so as to intersect the extension line of the rotation center of the second table rotating shaft of the second holding table on the extension line of the rotation center of the second rotating shaft; a second cutting blade mounted on the tip of the second rotating shaft is cut into the curved surface so as not to contact the innermost circumference of the curved surface, and the second holding table is rotated around the second table rotating shaft, thereby forming a second stepped portion at the outer circumference of the workpiece in a second cutting step.

[0012] Preferably, in the second cutting step, the distance from the bottom surface of the second stepped portion to the first surface is set to be equal to or less than the distance from the lowermost end of the first stepped portion to the first surface.

[0013] Preferably, in the second cutting step, the distance from the bottom surface of the second stepped portion to the first surface is set to be greater than the distance from the lowermost end of the first stepped portion to the first surface.

[0014] Preferably, in the second cutting step, the first cutting blade used in the first cutting step is used as the second cutting blade, or in the second cutting step, a cutting blade having the same material, the same structure, and the same shape as the first cutting blade is used as the second cutting blade.

[0015] Preferably, the method for processing the workpiece further includes a grinding step of grinding the first surface of the workpiece after the second cutting step so that the thickness of the workpiece is equal to or less than the distance from the bottom surface of the second stepped portion formed in the second cutting step to the first surface.

Advantages of the Invention

[0016] In the method for processing a workpiece according to one aspect of the present invention, after holding the first surface of the workpiece by the first holding table, the extension line of the rotation center of the first rotation axis is arranged so as not to intersect the extension line of the rotation center of the first table rotation axis, and the first cutting blade mounted on the tip of the first rotation axis is cut into the outer peripheral portion of the second surface of the workpiece, and then the first holding table is rotated around the first table rotation axis (first cutting step).

[0017] In this first cutting step, the workpiece can be mainly cut by the outer peripheral side surface of the first cutting blade. Specifically, the workpiece can be cut by the lower end portion of the outer peripheral side surface and the arc-shaped region of the outer peripheral side surface from the lower end portion to a predetermined height position. Thereby, a first stepped portion having a curved surface is formed on the outer peripheral portion of the second surface of the workpiece.

[0018] In the first cutting step, the workpiece can be mainly cut by the outer peripheral side surface of the first cutting blade, and the contact between one surface of the first cutting blade and the workpiece can be substantially prevented. Therefore, when removing the chamfered portion on the outer peripheral portion of the second surface of the workpiece, the number and size of chippings can be reduced, and film peeling can be suppressed.

[0019] In addition, after the first cutting step, the extension line of the rotation center of the second rotation axis is arranged so as to intersect the extension line of the rotation center of the second table rotation axis, and the second cutting blade mounted on the tip of the second rotation axis is cut into the curved surface so as not to contact the innermost circumference of the above-described curved surface, and then the second holding table is rotated around the second table rotation axis. Thereby, a second stepped portion is formed on the outer peripheral portion of the workpiece (second cutting step).

[0020] In the second cutting process, since the second cutting blade does not contact the innermost circumference of the curved surface formed in the first cutting process, chipping is not newly formed and no new film peeling occurs at the outermost circumference of the flat region of the second surface of the workpiece (i.e., the innermost circumference of the curved surface).

[0021] In addition, if the thickness from the bottom surface of the second step portion formed in the second cutting process to the second surface is set to be equal to or less than the finish thickness, after the grinding process, the curved surface connected to the first surface can be eliminated. That is, it is possible to prevent a sharp edge from remaining at the outer peripheral portion of the first surface after the grinding process.

Brief Description of the Drawings

[0022]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0023] (First Embodiment) With reference to the accompanying drawings, an embodiment according to one aspect of the present invention will be described. FIG. 1 is a flowchart of a method for machining a workpiece 11. In the first embodiment, the steps are performed in the order of the first cutting step S10, the second cutting step S20, and the grinding step S30.

[0024] First, with reference to FIG. 2, a cutting device 2 for performing the first cutting step S10 and the second cutting step S20 will be described. FIG. 2 is a perspective view of the cutting device 2. The X-axis direction (machining feed direction), the Y-axis direction (indexing feed direction), and the Z-axis direction (vertical direction, up and down direction) shown in FIG. 2 are orthogonal to each other.

[0025] The cutting device 2 has a base portion 4 that supports or houses each component. Above the base portion 4, a plurality of exterior panels 6 that cover the base portion 4 are provided. A predetermined space is formed inside the box defined by the plurality of exterior panels 6.

[0026] In this predetermined space, for example, a cutting unit 8 for cutting (i.e., machining) the workpiece 11 is arranged. The cutting device 2 of the present embodiment has one cutting unit 8. However, the cutting device 2 may have a parallel dual structure including two cutting units 8 arranged symmetrically with respect to the XZ plane like the left and right hands.

[0027] The cutting unit 8 has a prismatic spindle housing 10 whose longitudinal direction is arranged substantially parallel to the Y-axis direction. A part of a cylindrical spindle (first rotation axis, second rotation axis) 12 is rotatably accommodated in the spindle housing 10 (see FIG. 4(A)).

[0028] The longitudinal direction of the spindle 12 is arranged along the Y-axis direction. That is, the spindle 12 is arranged along the XY plane. A motor (not shown) is provided at a part near the base end portion of the spindle 12.

[0029] As shown in Fig. 4(A), a cutting blade (first cutting blade, second cutting blade) 14 having an annular cutting edge 14a is mounted on the tip 12a of the spindle 12. When the spindle 12 is rotated by a motor, the cutting blade 14 also rotates integrally.

[0030] Returning to Fig. 2, a microscope camera unit 16 is fixed to one side surface of the spindle housing 10. The microscope camera unit 16 includes a light source (not shown) such as an LED (Light Emitting Diode), an optical system (not shown) including a condenser lens, and a solid-state imaging device (not shown).

[0031] The image obtained by the microscope camera unit 16 capturing the workpiece 11 is used for alignment, kerf check, etc. The spindle housing 10 and the microscope camera unit 16 are fixed to the lower end of the Z-axis direction moving plate 18.

[0032] The Z-axis direction moving plate 18 is movable along the Z-axis direction by a Z-axis direction moving mechanism (not shown) having a ball screw. The Z-axis direction moving mechanism is fixed to a Y-axis direction moving plate (not shown).

[0033] The Y-axis direction moving plate is movable along the Y-axis direction by a Y-axis direction moving mechanism (not shown) having a ball screw. The positions of the cutting blade 14 and the microscope camera unit 16 in the Y-axis direction and the Z-axis direction are adjusted by the Y-axis direction moving mechanism and the Z-axis direction moving mechanism.

[0034] The position of the lower end of the cutting edge 14a of the cutting blade 14 that rotates at high speed around the spindle 12 in the Z-axis direction is also adjusted by the Z-axis direction moving mechanism, and the position of the lower end of the cutting edge 14a in the Y-axis direction is also adjusted by the Y-axis direction moving mechanism.

[0035] Below the spindle housing 10, a disk-shaped chuck table (first holding table, second holding table) 20 for sucking and holding the workpiece 11 is provided. The chuck table 20 has a disk-shaped frame body formed of metal.

[0036] On the upper surface of the frame body, a disk-shaped concave portion having a smaller diameter than the outer diameter of the outer periphery of the frame body is formed. A disk-shaped porous plate having substantially the same diameter as the concave portion is fixed to this concave portion. The porous plate is formed of, for example, porous ceramics. A suction source (not shown) such as a vacuum pump is connected to the porous plate via the frame body.

[0037] The negative pressure generated by the suction source can be transmitted to the upper surface of the porous plate. The upper surfaces of the frame body and the porous plate are substantially flush, and constitute a substantially flat holding surface (first holding surface, second holding surface) 20a along the XY plane. That is, the above-described spindle 12 is arranged along the holding surface 20a.

[0038] A rotary drive mechanism (not shown) such as a motor is provided at the bottom of the chuck table 20. By operating this rotary drive mechanism, the chuck table 20 rotates around a table rotation axis (first table rotation axis, second table rotation axis) 22 (see FIGS. 4(B) and 4(C)).

[0039] In FIGS. 4(B) and 4(C), the table rotation axis 22 is simplified and shown by a straight line corresponding to the rotation center of the table rotation axis 22. Since the extension line 22a of the rotation center of the table rotation axis 22 is arranged substantially parallel to the Z-axis direction, it is arranged so as to be orthogonal to the holding surface 20a.

[0040] Incidentally, the chuck table 20 may have an annular holding surface and a cylindrical suction holding portion (not shown). In this case, a plurality of suction holes are provided at substantially equal intervals along the circumferential direction of the holding surface on the annular holding surface.

[0041] The chuck table 20 sucks and holds, by means of the annular holding surface, not the entire back surface (first surface) 11b of the workpiece 11, but the inside in the radial direction of the back surface 11b rather than the outer peripheral end portion.

[0042] Even when the chuck table 20 has an annular holding surface, the center of rotation of the table rotation axis 22 is arranged at the center of the outer diameter of the holding surface 20a, and the center of rotation of the table rotation axis 22 and the holding surface 20a are arranged to be orthogonal to each other.

[0043] The rotation drive mechanism and the chuck table 20 are supported by an X-axis direction moving plate (not shown). The X-axis direction moving plate is configured to be movable along the X-axis direction by an X-axis direction moving mechanism (not shown) having a ball screw. The relative position in the X-axis direction between the lower end of the cutting blade 14a and the workpiece 11 is adjusted by the X-axis direction moving mechanism.

[0044] Returning to FIG. 2, a touch panel 24 is provided on the front surface 6a of the exterior panel 6 of the cutting device 2. The touch panel 24 serves as an input device for an operator to input instructions to a controller described later, and a display device for displaying an image acquired by the microscope camera unit 16, a display window for displaying machining conditions, a GUI (Graphical User Interface), etc.

[0045] Near the front surface 6a, a cassette mounting table 6b is provided. A cassette (not shown) containing one or a plurality of workpieces 11 is placed on the cassette mounting table 6b. The cassette mounting table 6b is movable along the Z-axis direction by an elevator (not shown). By adjusting the height of the cassette mounting table 6b by the elevator, the height of the workpiece 11 carried into and out of the cutting device 2 by the transfer mechanism is adjusted.

[0046] The operations of the cutting unit 8, the Y-axis direction moving mechanism, the Z-axis direction moving mechanism, the microscope camera unit 16, the chuck table 20, the X-axis direction moving mechanism, the touch panel 24, etc. are controlled by a controller (not shown).

[0047] The controller is constituted by a computer including a processor represented by, for example, a CPU (Central Processing Unit) and a memory. The memory includes a main storage device such as a DRAM (Dynamic Random Access Memory) and an auxiliary storage device such as a flash memory, an HDD (Hard Disk Drive), and an SSD (Solid State Drive).

[0048] The auxiliary storage device stores software including a predetermined program. By operating a processor or the like according to this program, the functions of the controller are realized. Next, the workpiece 11 to be cut (machined) by the cutting device 2 will be described.

[0049] FIG. 3(A) is a perspective view of the workpiece 11, and FIG. 3(B) is a cross-sectional view taken along line AA of the workpiece 11. The workpiece 11 includes, for example, a disk-shaped (plate-shaped) semiconductor substrate (i.e., a wafer) formed of a semiconductor material such as single crystal silicon.

[0050] However, there are no restrictions on the material, shape, structure, size, etc. of the wafer constituting the workpiece 11. The workpiece 11 may be a so-called bonded wafer in which two wafers having substantially the same diameter are bonded via an adhesive or the like.

[0051] The workpiece 11 has surfaces (second surfaces) 11a and back surfaces (first surfaces) 11b that are located on opposite sides in the thickness direction 11c. The thickness of the workpiece 11 in the present embodiment is 775 μm.

[0052] As shown in FIG. 3(B), chamfered portions 11a1 and 11b1 (i.e., bevel portions) are formed on the outer peripheral portions of the surface 11a and the back surface 11b of the workpiece 11, respectively. The diameter of the workpiece 11 is defined by the outer peripheral end portion 11d. The diameter of the workpiece 11 in the present embodiment is 300 mm.

[0053] Before cutting, the outer peripheral end portion 11d becomes the boundary between the chamfered portion 11a1 of the front surface 11a and the chamfered portion 11b1 of the back surface 11b. In FIG. 3(B), a point is marked at the radial center 11a2 of the front surface 11a.

[0054] As shown in FIG. 3(A), a plurality of division planned lines 13 are set in a grid pattern on the front surface 11a of the workpiece 11. Devices 15 such as ICs (Integrated Circuits) are formed in each rectangular region partitioned by the plurality of division planned lines 13.

[0055] Note that there are no restrictions on the type, quantity, shape, structure, size, arrangement, etc. of the device 15. The workpiece 11 may not have the device 15. Next, referring to FIGS. 4(A) to 5(B), the first cutting step S10 will be described.

[0056] FIG. 4(A) is a plan view of the first cutting step S10. FIG. 4(B) is a side view of the first cutting step S10 as viewed in the direction of arrow A1 in FIG. 4(A), and FIG. 4(C) is a side view of the first cutting step S10 as viewed in the direction of arrow A2 in FIG. 4(A).

[0057] In FIGS. 4(A) to 4(C), the extension line 12b of the rotation center of the spindle 12 is indicated by a dashed-dotted line parallel to the Y-axis direction (see FIGS. 4(A) and 4(B)) or a point (see FIG. 4(C)), and the extension line 22a of the rotation center of the table rotation axis 22 is indicated by a point (see FIG. 4(A)) or a dashed-dotted line parallel to the Z-axis direction (see FIGS. 4(B) and 4(C)).

[0058] In the first cutting step S10, first, the workpiece 11 is placed on the chuck table 20 so that the center 11a2 of the front surface 11a substantially coincides with the center of the holding surface 20a (corresponding to the extension line 22a in FIG. 4(A)). At this time, the front surface 11a is exposed upward, and the back surface 11b is in contact with the holding surface 20a. Then, the workpiece 11 is sucked and held by the holding surface 20a by negative pressure.

[0059] Thereafter, while supplying cutting fluid such as pure water to the cutting blade 14, the cutting blade 14 is rotated at high speed around the spindle 12, and the position of the cutting blade 14 relative to the workpiece 11 is adjusted.

[0060] Specifically, on the extension line 12b of the rotation center of the spindle 12, the relative positions of the chuck table 20 and the cutting unit 8 are adjusted so that the extension line 12b and the extension line 22a of the rotation center of the table rotation axis 22 do not intersect. At this time, the angle α formed by the straight line 26 shown in FIG. 4(A) and the straight line parallel to the Y axis is made greater than 0 degrees and less than 90 degrees (0 degrees < α < 90 degrees).

[0061] As shown in FIG. 4(A), this straight line 26 is a straight line connecting the intersection point 14c where the outer surface 14b of the holding nut for fixing the cutting blade 14 to the spindle 12 intersects the extension line 12b of the rotation center of the spindle 12, and a point on the extension line 22a of the rotation center of the table rotation axis 22 in the XY plane including the extension line 12b.

[0062] In one example, α is a predetermined value of 5 degrees or more and 45 degrees or less. The cutting unit 8 is arranged in this way, and the cutting edge 14a of the cutting blade 14 is cut into the outer peripheral portion of the surface 11a to a predetermined depth that does not reach from the front surface 11a to the back surface 11b.

[0063] With the cutting edge 14a cut into the outer peripheral portion, the chuck table 20 is rotated 360 degrees or more at a predetermined speed around the table rotation axis 22, thereby cutting the outer peripheral portion of the surface 11a. An example of the cutting conditions in the first cutting step S10 is shown below.

[0064] Rotation speed of the spindle: 30000 (rpm) Flow rate of the cutting fluid: 4.5 (L / min) Width in the radial direction of the workpiece to be removed: 1.0 (μm) to 3.0 (μm) Angle α: 45 (degrees) Rotation speed of the chuck table: 3 (degrees / s) to 5 (degrees / s) Depth of cut from the surface: from 100 (μm) to 150 (μm)

[0065] The flow rates of the above-mentioned cutting fluid are all the total values of the flow rates of the cutting fluid supplied from a pair of cooler nozzles (not shown), a shower nozzle, and a spray nozzle. The pair of cooler nozzles are arranged so as to sandwich the cutting edge 14a in the thickness direction of the cutting edge 14a (i.e., the direction from one surface 14a2 of the cutting edge 14a to the other surface), and the cutting fluid is supplied from the pair of cooler nozzles to the lower end portion of the cutting edge 14a. The flow rate of the cutting fluid supplied from the pair of cooler nozzles is, for example, 1.5 L / min.

[0066] The shower nozzle is arranged between the pair of cooler nozzles in the Y-axis direction, and the cutting fluid is supplied from the shower nozzle to the outer peripheral portion of the cutting edge 14a. The flow rate of the cutting fluid supplied from the shower nozzle is, for example, 2.0 L / min. The spray nozzle is arranged in the vicinity of the shower nozzle, and the cutting fluid is supplied from the spray nozzle to the surface 11a of the workpiece 11. The flow rate of the cutting fluid supplied from the spray nozzle is, for example, 1.0 L / min.

[0067] In the first cutting step S10, the workpiece 11 can be mainly cut by the outer peripheral side surface 14a1 of the cutting edge 14a. Specifically, the workpiece 11 can be cut by the lower end portion of the outer peripheral side surface 14a1 and the arc-shaped region of the outer peripheral side surface 14a1 from this lower end portion to a predetermined height position located below the rotation center of the spindle 12.

[0068] In the first cutting step S10, the contact between the one surface 14a2 of the cutting edge 14a and the workpiece 11 can be substantially prevented. Therefore, when removing the chamfered portion 11a1 on the outer peripheral portion of the surface 11a of the workpiece 11, the number and size of chippings can be reduced, and film peeling can be suppressed.

[0069] FIG. 5(A) is a cross-sectional view corresponding to FIG. 3(B) of the workpiece 11 after the first cutting step S10. In this specification, the cross-sectional view of the workpiece 11 is a cross-section in a plane passing through the center 11a2 of the surface 11a and perpendicular to the surface 11a. FIG. 5(B) is an enlarged view of a part of the region indicated by the dashed square in FIG. 5(A).

[0070] In the first cutting step S10, an annular first stepped portion 17 is formed on the outer peripheral portion of the surface 11a of the workpiece 11. The first stepped portion 17 has an annular curved surface 17a that depresses from the surface 11a toward the back surface 11b as it proceeds outward from the center 11a2 of the surface 11a, and a substantially flat annular bottom surface 17b.

[0071] As shown in FIGS. 5(A) and 5(B), the curved surface 17a is not a cylindrical side surface or a frustum of a cone side surface, but depresses toward the back surface 11b side from a virtual straight line connecting the outermost periphery 17a1 and the innermost periphery 17a2 of the curved surface 17a.

[0072] The innermost periphery of the bottom surface 17b is connected to the outermost periphery 17a1 of the curved surface 17a. In the present embodiment, the outermost periphery of the bottom surface 17b becomes the outer peripheral end portion 11d of the workpiece 11 after the first cutting step S10.

[0073] In the present embodiment, the outer peripheral end portion 11d of the first stepped portion 17 after the first cutting step S10 coincides with the outer peripheral end portion 11d before the cutting process. However, depending on the finish thickness 21, the outer peripheral end portion 11d before and after the cutting process does not necessarily have to coincide.

[0074] After the first cutting step S10, a second cutting step S20 is performed. In the present embodiment, the cutting blade 14 used in the first cutting step S10 is continuously used to perform the second cutting step S20. That is, in the second cutting step S20, the cutting blade 14 used in the first cutting step S10 is used.

[0075] FIG. 6(A) is a plan view of the second cutting step S20, FIG. 6(B) is a side view of the second cutting step S20 viewed in the direction of arrow A3 in FIG. 6(A), and FIG. 6(C) is a side view of the second cutting step S20 viewed in the direction of arrow A4 in FIG. 6(A).

[0076] In the second cutting step S20, first, with the rotation of the chuck table 20 stopped, the cutting blade 14 is rotated at high speed while supplying cutting water to the cutting blade 14, and the position of the cutting blade 14 with respect to the workpiece 11 is adjusted.

[0077] Specifically, on the extension line 12b of the rotation center of the spindle 12, the relative positions of the chuck table 20 and the cutting unit 8 are adjusted so that the extension line 12b intersects the extension line 22a of the rotation center of the table rotation axis 22.

[0078] More specifically, the position of the chuck table 20 in the Y-axis direction with respect to the spindle 12 is adjusted so that the extension line 12b is orthogonal to the extension line 22a. That is, in the XY plane including the extension line 12b, the angle formed by the straight line 26 connecting a point on the extension line 22a and the intersection point 14c with the Y-axis direction is approximately 0 degrees.

[0079] While arranging the cutting unit 8 in this way and cutting into the curved surface 17a and the bottom surface 17b so that the cutting edge 14a of the cutting blade 14 does not contact the innermost circumference 17a2 of the curved surface 17a, the chuck table 20 is rotated 360 degrees or more at a predetermined speed around the table rotation axis 22. An example of the cutting conditions in the second cutting step S20 is shown below.

[0080] Rotation speed of the spindle: 30000 (rpm) Flow rate of cutting water: 4.5 (L / min) Width in the radial direction of the workpiece of the remaining curved surface: 5 (μm) Rotation speed of the chuck table: 3 (degrees / s) to 5 (degrees / s) Cutting depth from the surface: Make it 10 μm deeper than the cutting depth in the first cutting step S10 (for example, from 110 μm to 160 μm from the surface 11a).

[0081] Incidentally, the flow rate of the cutting fluid described above is the total value of the flow rate of the cutting fluid supplied from a pair of coolant nozzles (for example, 1.5 L / min), the flow rate of the cutting fluid supplied from the shower nozzle (for example, 2.0 L / min), and the flow rate of the cutting fluid supplied from the spray nozzle (for example, 1.5 L / min).

[0082] In the second cutting step S20 of the present embodiment, the first stepped portion 17 outside the innermost circumference 17a2 of the curved surface 17a is cut to a position deeper than the bottom surface 17b. At this time, the cutting blade 14 does not contact the innermost circumference 17a2 of the curved surface 17a formed in the first cutting step S10.

[0083] Therefore, chipping is not newly formed at the outermost circumference of the flat region of the surface 11a of the workpiece 11 (that is, the innermost circumference 17a2 of the curved surface 17a), and no new film peeling starting from the outermost circumference of the flat region occurs.

[0084] FIG. 7(A) is a cross-sectional view of the workpiece 11 after the second cutting step S20 and corresponds to FIG. 3(B). FIG. 7(B) is an enlarged view of a part of the region indicated by the dashed square in FIG. 7(A). In the second cutting step S20, the second stepped portion 19 is formed on the outer peripheral portion of the workpiece 11.

[0085] The second stepped portion 19 has a cylindrical side surface 19a located outside the innermost circumference 17a2 of the curved surface 17a in the radial direction of the workpiece 11 and a substantially flat annular bottom surface 19b formed at a position deeper than the outermost circumference 17a1 of the curved surface 17a.

[0086] As shown in FIG. 7(B), in the second cutting step S20, the distance 19c from the annular bottom surface 19b of the second stepped portion 19 to the back surface 11b is made equal to or less than the distance 17c from the annular bottom surface 17b located at the lowermost end of the first stepped portion 17 to the back surface 11b.

[0087] After the second cutting step S20, a grinding step S30 is performed. First, referring to FIGS. 8(A) and 8(B), a grinding apparatus 30 used in the grinding step S30 will be described. The grinding apparatus 30 has a grinding unit 32.

[0088] The grinding unit 32 has a columnar spindle 34 disposed substantially parallel to the Z-axis direction. A part of the spindle 34 is rotatably accommodated in a cylindrical spindle housing (not shown) using an air bearing or the like.

[0089] A motor (not shown) is provided near the upper end of the spindle 34. A Z-axis direction movement mechanism (not shown) having a ball screw is connected to the spindle housing, and the spindle housing is movable along the Z-axis direction together with the spindle 34.

[0090] The bottom of the spindle 34 protrudes below the bottom of the spindle housing, and the center of a disc-shaped wheel mount 36 is fixed to the bottom of the spindle 34. A grinding wheel 38 having substantially the same diameter as the wheel mount 36 is mounted on the bottom surface of the wheel mount 36.

[0091] The grinding wheel 38 has an annular wheel base 38a formed of a metal material such as an aluminum alloy. A plurality of grinding wheels 38b are fixed to the lower surface side of the wheel base 38a. The plurality of grinding wheels 38b are arranged at substantially equal intervals along the circumferential direction of the wheel base 38a.

[0092] The grinding wheel 38b is formed, for example, by mixing abrasive grains such as diamond and cBN (cubic Boron Nitride) into a binder (i.e., bond material) such as metal, ceramics, and resin, and then undergoing molding, firing, and the like.

[0093] Below the grinding unit 32, a grinding water supply unit including a nozzle (not shown) for supplying grinding water such as pure water to the grinding area is provided. Also, a disc-shaped chuck table 40 is provided below this nozzle.

[0094] The chuck table 40 is rotatably supported by a disk-shaped table base 42 including bearings. A cylindrical rotating shaft 44 is connected to the bottom of the chuck table 40. In FIGS. 8(A) and 8(B), the rotating shaft 44 is simplified and shown by a dashed-dotted line.

[0095] The rotating shaft 44 is inserted into a through hole (not shown) formed in the table base 42. A driven pulley (not shown) is fixed to the bottom of the rotating shaft 44. Further, in the vicinity of the rotating shaft 44, a motor (not shown) and a driving pulley (not shown) fixed to the output shaft of the motor are provided.

[0096] An endless belt (not shown) is wound around the driven pulley and the driving pulley, and the power of the motor is transmitted to the rotating shaft 44 via the endless belt or the like. The table base 42 is supported by an inclination adjusting mechanism (not shown), and the inclination with respect to the Z-axis direction is adjusted by the inclination adjusting mechanism.

[0097] The chuck table 40 has a disk-shaped frame body 46 formed of non-porous ceramics or the like as shown in FIG. 8(B). A disk-shaped recess is formed on the upper surface of the frame body 46. A disk-shaped porous plate 48 formed of porous ceramics is fixed to the recess with an adhesive or the like.

[0098] The porous plate 48 has a substantially flat bottom surface, a cylindrical side surface, and a conical upper surface in which the central portion protrudes slightly (for example, by a predetermined value of 10 μm or more and 30 μm or less) compared with the outer peripheral portion. In FIG. 8(B), the shape of the upper surface is exaggerated.

[0099] The upper surface of the porous plate 48 and the upper surface of the frame body 46 are substantially flush with each other, and constitute a holding surface 40a for sucking and holding the workpiece 11. The inclination of the chuck table 40 is adjusted by the above-described inclination adjusting mechanism so that a part of the holding surface 40a is substantially parallel to the XY plane orthogonal to the Z-axis direction.

[0100] When negative pressure is transmitted from a suction source (not shown) such as a vacuum pump to the porous plate 48 via the frame body 46, the workpiece 11 is deformed so as to follow the shape of the holding surface 40a and is suction-held by the holding surface 40a.

[0101] FIG. 8(A) is a perspective view of the grinding process S30, and FIG. 8(B) is a partial cross-sectional side view of the grinding process S30. In the grinding process S30, first, in order to protect the device 15, a protective tape (not shown) made of resin and having substantially the same diameter as the surface 11a is attached to the surface 11a.

[0102] Then, the workpiece 11 is arranged on the holding surface 40a so that the center 11a2 of the surface 11a substantially coincides with the radial center of the holding surface 40a. At this time, the back surface 11b is exposed upward, and the surface 11a faces the holding surface 40a via the protective tape.

[0103] Then, the spindle 34 and the rotating shaft 44 are rotated at predetermined rotational speeds, and while supplying grinding water from the nozzle to the contact area between the grinding wheel 38b and the workpiece 11, the grinding unit 32 is moved downward along the Z-axis direction at a predetermined speed (i.e., grinding feed).

[0104] The grinding process S30 includes, for example, a rough grinding process using a rough grinding wheel with a rough grinding wheel mounted as the grinding wheel 38b, and a finish grinding process using a finish grinding wheel with a finish grinding wheel mounted as the grinding wheel 38b after the rough grinding process. The rough grinding wheel has, for example, a grit size of #320, and the finish grinding wheel has, for example, a grit size of #2000.

[0105] The grit size represents the size of the abrasive grains. For the grit size, refer to JIS R 6001-2:2017 (Grit size of grinding and honing abrasives - Part 2: Fine powder) specified in the Japanese Industrial Standards (JIS). An example of the grinding conditions is shown below. Note that the length of time for rough grinding and the length of time for finish grinding are appropriately determined according to the thickness of the workpiece 11 removed by grinding.

[0106] (Rough grinding conditions) Spindle rotation speed: 3000 (rpm) Chuck table rotation speed: 300 (rpm) Grinding feed rate: 3.0 (μm / s) Flow rate of grinding water: 4.0 (L / min)

[0107] (Finish grinding conditions) Spindle rotation speed: 3000 (rpm) Chuck table rotation speed: 300 (rpm) Grinding feed rate: 0.3 (μm / s) Flow rate of grinding water: 4.0 (L / min)

[0108] By uniformly grinding the back surface 11b of the workpiece 11 with the grinding wheel 38, the thickness of the workpiece 11 is made to be equal to or less than the distance 19d from the bottom surface 19b of the second step portion 19 formed in the second cutting step S20 to the surface 11a.

[0109] That is, as shown in FIGS. 9(A) and 9(B), in the grinding step S30, the back surface 11b side of the workpiece 11 is removed by a thickness equal to or greater than the distance 19c corresponding to the distance from the bottom surface 19b of the second step portion 19 to the back surface 11b at the time of the second cutting step S20.

[0110] FIG. 9(A) is a cross-sectional view of the workpiece 11 after the grinding step S30 and corresponds to FIG. 3(B). FIG. 9(B) is an enlarged view of a part of the region indicated by the square broken line in FIG. 9(A).

[0111] By setting the distance 19d from the bottom surface 19b of the second step portion 19 formed in the second cutting step S20 to the surface 11a to be equal to or less than the finish thickness 21, after the completion of the grinding step S30, the curved surface 17a connected to the back surface 11b can be eliminated. That is, it is possible to prevent a sharp edge from remaining on the outer peripheral portion of the back surface 11b after the grinding step S30.

[0112] Thus, in this embodiment, in the first cutting step S10, the workpiece 11 can be mainly cut by the outer peripheral side surface 14a1 of the cutting edge 14a, and contact between the one surface 14a2 of the cutting edge 14a and the workpiece 11 can be substantially prevented. Therefore, the number and size of chippings on the surface 11a can be reduced, and film peeling on the surface 11a can be suppressed.

[0113] Furthermore, in the second cutting step S20, although the arrangement of the cutting unit 8 with respect to the workpiece 11 is the same as that of the conventional edge trimming, the portion outside the innermost circumference 17a2 of the first stepped portion 17 in the radial direction of the workpiece 11 is cut deeper than the first stepped portion 17.

[0114] Then, by setting the distance 19d from the bottom surface 19b of the second stepped portion 19 to the surface 11a to be equal to or less than the finish thickness 21, after the grinding step S30 is completed, the curved surface 17a connected to the back surface 11b can be eliminated. As a result, as will be described later, the sharp edge remaining on the back surface 11b after the grinding step S30 can be eliminated.

[0115] By the way, in the first cutting step S10 and the second cutting step S20 of the first embodiment, the same cutting blade 14 is used. However, instead of this, when the cutting device 2 has the above-described parallel dual structure, or when another cutting device 2 different from the cutting device 2 is used, in the second cutting step S20, another cutting blade 14 having the same material, the same structure, and the same shape as the cutting blade 14 may be used.

[0116] Having the same material as the cutting blade 14 means that in another cutting blade14, the material of the abrasive grains and the material of the bonding material are the same as those of the cutting blade 14, respectively. Also, having the same structure as the cutting blade 14 means that in another cutting blade 14, the average particle diameter (or grain size) and the concentration of the abrasive grains are the same as those of the cutting blade 14. Furthermore, having the same shape as the cutting blade 14 means that in another cutting blade 14, the blade width and the tip shape of the cutting edge 14a are the same as those of the cutting blade 14.

[0117] Incidentally, the second cutting step S20 may be performed using another cutting blade 14 different from the cutting blade 14 used in the first cutting step S10. When different cutting blades 14 are used in the first cutting step S10 and the second cutting step S20, in the first cutting step S10, by using the cutting blade 14 having coarse abrasive grains, the removal amount of the workpiece 11 per unit time can be improved.

[0118] On the other hand, in the second cutting step S20, when using a cutting blade 14 containing finishing abrasive grains having an average particle size smaller than the average particle size of the coarse abrasive grains, compared with the case of using a cutting blade 14 having coarse abrasive grains, the cutting blade 14 is more likely to be consumed, but the number and size of chipping formed on the cylindrical side surface 19a in the second cutting step S20 can be further reduced.

[0119] Incidentally, in the first cutting step S10 and the second cutting step S20 of the first embodiment, the same chuck table 20 is used. Similarly, when the cutting device 2 has a parallel dual structure, in the first cutting step S10 and the second cutting step S20, the same chuck table 20 is used.

[0120] On the other hand, when performing the first cutting step S10 and the second cutting step S20 using two different cutting devices 2, different chuck tables 20 are used in the first cutting step S10 and the second cutting step S20.

[0121] Note that different chuck tables 20 include cases where they are manufactured from the same material and have the same shape but different manufacturing numbers, cases where the materials and shapes are different, etc. That is, different chuck tables 20 mean chuck tables 20 that occupy different spaces from each other.

[0122] (Second Embodiment) Next, referring to FIGS. 10(A) to 10(C), the second embodiment will be described. FIG. 10(A) is an enlarged view of a part of the cross-section of the workpiece 11 after the first cutting step S10 and before the second cutting step S20 of the second embodiment. Since the first cutting step S10 is the same as that of the first embodiment, the description thereof will be omitted.

[0123] Figure 10(B) is an enlarged view of a part of the cross-section of the workpiece 11 after the second cutting step S20 and before the grinding step S30 of the second embodiment. In the second cutting step S20 of the second embodiment, the cutting blade 14 is arranged to cut the workpiece 11 so as not to contact the bottom surface 17b on the outer side of the innermost circumference 17a2 and on the inner side of the outermost circumference 17a1 of the curved surface 17a in the radial direction of the workpiece 11.

[0124] Thereby, an annular second stepped portion 19 is formed over the entire circumference of the annular curved surface 17a in a part from the outermost circumference 17a1 to the innermost circumference 17a2. The distance 19c from the bottom surface 19b of the second stepped portion 19 to the back surface 11b is larger than the distance 17c from the lowermost end (i.e., the bottom surface 17b) of the first stepped portion 17 to the back surface 11b.

[0125] Figure 10(C) is an enlarged view of a part of the cross-section of the workpiece 11 after the grinding step S30 of the second embodiment. In the grinding step S30, the back surface 11b side of the workpiece 11 is removed by a thickness equal to or greater than the distance 19c from the bottom surface 19b of the second stepped portion 19 to the back surface 11b at the time of the second cutting step S20.

[0126] In the second embodiment, the finish thickness 21 is set to be equal to or less than the distance 19d from the bottom surface 19b to the surface 11a. Thereby, after the grinding step S30 is completed, the curved surface 17a connected to the back surface 11b can be eliminated.

[0127] Therefore, similar to the first embodiment, it is possible to prevent a sharp edge from remaining on the outer peripheral portion of the back surface 11b after the grinding step S30. However, in the grinding step S30 of the second embodiment, the relatively thin annular region 23 (see Figure 10(C)) that constituted the curved surface 17a will be removed in the grinding step S30. In Figure 10(C), hatching is applied to the annular region 23 for easy understanding.

[0128] The annular region 23 is prone to chipping during grinding due to its thinness. Therefore, the processing quality in the grinding step S30 may be better in the first embodiment. Note that also in the second embodiment, effects such as reduction in the number and size of chippings and suppression of film peeling on the surface 11a can be achieved.

[0129] Note that the finish thickness 21 shown in FIG. 10(C) is drawn thinner than the finish thickness 21 in the first embodiment shown in FIG. 9(B), but this is only for convenience of explanation, and by adjusting the depths of the first step portion 17 and the second step portion 19, etc., it may be made the same as the finish thickness 21 of the first embodiment.

[0130] (Third Embodiment) Next, referring to FIGS. 11(A) to 12(B), the third embodiment will be described. FIG. 11(A) is a plan view of the first cutting step S10 of the third embodiment, corresponding to FIG. 4(A) in the first embodiment.

[0131] FIG. 11(B) is a cross-sectional view of the workpiece 11 after the first cutting step S10 of the third embodiment, corresponding to FIG. 3(B). FIG. 11(C) is an enlarged view of a part of the region indicated by the square broken line in FIG. 11(B).

[0132] In the first cutting step S10 of the third embodiment, in the XY plane, the angle β formed by the straight line 26 connecting the intersection point 14c and a point on the extension line 22a with a straight line parallel to the Y axis is larger than α in the first embodiment and smaller than 90 degrees (0 degrees < α < β < 90 degrees).

[0133] The third embodiment is different from the first embodiment in this regard. Other points are the same as those in the first embodiment. Due to such a difference in the cutting mode, the first step portion 17 formed in the first cutting step S10 does not have a substantially flat annular bottom surface 17b, but only has a curved surface 17a that depresses from the surface 11a toward the back surface 11b as it proceeds outward from the center 11a2 of the surface 11a.

[0134] That is, the outermost periphery 17a1 of the curved surface 17a becomes the outer peripheral end portion 11d of the workpiece 11. The outer peripheral end portion 11d may or may not coincide with the outer peripheral end portion 11d of the workpiece 11 before cutting. After the first cutting step S10, the second cutting step S20 is performed.

[0135] FIG. 12(A) is an enlarged view of a part of the cross section of the workpiece 11 after the second cutting step S20 of the third embodiment. In the second cutting step S20, similarly to the first embodiment, a second stepped portion 19 is formed on the outer peripheral portion of the workpiece 11.

[0136] The second stepped portion 19 has a cylindrical side surface 19a located outside the innermost periphery 17a2 of the curved surface 17a in the radial direction of the workpiece 11, and an annular bottom surface 19b that is the same as or closer to the back surface 11b than the outermost periphery 17a1 of the curved surface 17a and is substantially flat.

[0137] As shown in FIG. 12(A), in the second cutting step S20, the distance 19c from the annular bottom surface 19b to the back surface 11b of the second stepped portion 19 is made equal to or less than the distance 17c from the lowermost end (i.e., the outermost periphery 17a1) of the first stepped portion 17 to the back surface 11b.

[0138] After the second cutting step S20, a grinding step S30 is performed. FIG. 12(B) is an enlarged view of a part of the cross section of the workpiece 11 after the grinding step S30 of the third embodiment. By uniformly grinding the back surface 11b of the workpiece 11 with a grinding wheel 38, the thickness of the workpiece 11 is made into a finished thickness 21 that is equal to or less than the distance 19d from the bottom surface 19b to the front surface 11a.

[0139] (Fourth Embodiment) Next, with reference to FIGS. 13(A) to 13(C), the fourth embodiment will be described. FIG. 13(A) is an enlarged view of a part of the cross section of the workpiece 11 after the first cutting step S10 of the fourth embodiment. The first cutting step S10 is the same as that of the third embodiment.

[0140] FIG. 13(B) is an enlarged view of a part of the cross section of the workpiece 11 after the second cutting step S20 of the fourth embodiment. In the second cutting step S20 of the fourth embodiment, a second stepped portion 19 is formed in the same manner as the second cutting step S20 of the second embodiment.

[0141] That is, the distance 19c from the bottom surface 19b to the back surface 11b of the second stepped portion 19 is made larger than the distance 17c from the lowermost end (i.e., the outermost periphery 17a1) of the first stepped portion 17 to the back surface 11b.

[0142] FIG. 13(C) is an enlarged view of a part of the cross section of the workpiece 11 after the grinding step S30 of the fourth embodiment. Also in the grinding step S30, the back surface 11b side of the workpiece 11 is removed by a thickness equal to or greater than the distance 19c.

[0143] (First Comparative Example) Next, referring to FIGS. 14(A) to 14(D), the first comparative example will be described. FIG. 14(A) is a plan view showing the cutting step of the first comparative example for the outer peripheral portion of the workpiece 11.

[0144] In the first comparative example, when initially forming a stepped portion on the outer peripheral portion of the workpiece 11, the angle formed by the straight line 26 with the Y-axis direction is made approximately 0 degrees as in the second cutting step S20 in the first to fourth embodiments.

[0145] With the cutting unit 8 arranged in this way, with the lower end of the cutting edge 14a of the cutting blade 14 cut into a predetermined depth between the front surface 11a and the back surface 11b, the chuck table 20 is rotated 360 degrees or more at a predetermined speed around the table rotation axis 22.

[0146] FIG. 14(B) is an enlarged view of a partial region indicated by the dashed square in FIG. 14(A). In the cutting step of the first comparative example, when cutting the outer peripheral portion of the workpiece 11 with the outer peripheral side surface 14a1 of the cutting edge 14a, as the workpiece 11 rotates, in the region 25, one surface 14a2 of the cutting edge 14a and the workpiece 11 come into contact.

[0147] One surface 14a2 of the cutting edge 14a is usually in a state where the abrasive grains are buried in the bonding material, and the abrasive grains are not appropriately exposed to the extent that they can cut the workpiece 11. Therefore, when the one surface 14a2 and the workpiece 11 come into contact, only physical damage is caused to the workpiece 11, and cutting is hardly performed, and chipping, film peeling, etc. will progress.

[0148] FIG. 14(C) is a plan view of the workpiece 11 after the cutting process, and FIG. 14(D) is an enlarged view of a partial region indicated by a dashed square in FIG. 14(C). In the first comparative example, compared with the first to fourth embodiments described above, the number and size of chippings 27 on the surface 11a increase, and film peeling on the surface 11a is likely to occur.

[0149] (Second Comparative Example) Next, referring to FIGS. 15(A) to 15(C), the second comparative example will be described. In the second comparative example, in the first to fourth embodiments, after forming the first stepped portion 17 on the outer peripheral portion of the surface 11a of the workpiece 11 in the first cutting step S10, the second cutting step S20 is omitted, and the process proceeds to the grinding step S30.

[0150] FIG. 15(A) is an enlarged view of a part of the cross section of the workpiece 11 after the first cutting step S10 of the second comparative example. The distance from the surface 11a in the thickness direction 11c to the bottom surface 17b of the first stepped portion 17 is larger than the distance from the surface 11a to the position corresponding to the finish thickness 21.

[0151] FIG. 15(B) is an enlarged view of a part of the cross section of the workpiece 11 during the grinding step S30 of the second comparative example. As shown in FIG. 15(B), in the grinding step S30 of the second comparative example, a relatively thin annular region 23 including the outermost periphery 17a1 of the curved surface 17a is removed, so chipping is likely to occur during grinding.

[0152] FIG. 15(C) is an enlarged view of a part of the cross section of the workpiece 11 after the grinding step S30 of the second comparative example. As shown in FIG. 15(C), after the grinding step S30 of the second comparative example, a sharp edge 29 remains on the outer peripheral portion of the back surface 11b.

[0153] In the second comparative example, as in the first to fourth embodiments, when performing the first cutting step S10 to remove the chamfered portion 11a1 on the outer peripheral portion of the surface 11a of the workpiece 11, the number and size of the chipping 27 can be reduced, and peeling of the film on the surface 11a can be suppressed.

[0154] However, since the second cutting step S20 is not performed, there is a problem that it is impossible to avoid the remaining sharp edge 29 on the outer peripheral portion of the back surface 11b after the grinding step S30.

[0155] As described above, the first to fourth embodiments have been described in comparison with the first and second comparative examples. However, the structure, method, etc. according to the first to fourth embodiments can be appropriately changed and implemented as long as they do not deviate from the scope of the object of the present invention.

[0156] For example, the first cutting step S10 and the second cutting step S20 can be performed using different cutting devices 2. In this case, the first cutting device (not shown) has a first spindle (first rotation axis) arranged substantially parallel to the Y-axis direction.

[0157] A first cutting blade is attached to the tip of the first spindle. Further, the first cutting device further includes a first chuck table (first holding table) rotatable around a first table rotation axis arranged substantially parallel to the Z-axis direction.

[0158] Similarly, the second cutting device (not shown) has a second spindle (second rotation axis) arranged substantially parallel to the Y-axis direction, and a second cutting blade is attached to the tip of the second spindle. Further, the second cutting device further includes a second chuck table (second holding table) rotatable around a second table rotation axis arranged substantially parallel to the Z-axis direction.

Explanation of reference numerals

[0159] 2: Cutting device, 4: Base portion, 6: Exterior panel, 6a: Front surface, 6b: Cassette mounting table 8: Cutting unit, 10: Spindle housing 11: Workpiece 11a: Surface (second surface), 11a1: Chamfered portion, 11a2: Center 11b: Back surface (first surface), 11b1: Chamfered portion, 11c: Thickness direction 11d: Outer peripheral end 12: Spindle (first rotation axis, second rotation axis), 12a: Tip end, 12b: Extension line 13: Predetermined dividing line 14: Cutting blade (first cutting blade, second cutting blade) 14a: Cutting edge, 14a1: Outer peripheral side surface, 14a2: One surface, 14b: Outer surface, 14c: Intersection point 15: Device 16: Microscope camera unit 17: First step portion, 17a: Curved surface, 17a1: Outermost periphery, 17a2: Innermost periphery 17b: Bottom surface, 17c: Distance 18: Z-axis direction moving plate 19: Second step portion, 19a: Cylindrical side surface, 19b: Bottom surface, 19c, 19d: Distance 20: Chuck table (first holding table, second holding table) 20a: Holding surface (first holding surface, second holding surface) 21: Finishing thickness, 23: Annular region 22: Table rotation axis (first table rotation axis, second table rotation axis), 22a: Extension line 24: Touch panel 25: Region, 26: Straight line 27: Chipping, 29: Sharp edge 30: Grinding device, 32: Grinding unit 34: Spindle, 36: Wheel mount 38: Grinding wheel, 38a: Wheel base, 38b: Grinding stone 40: Chuck table, 40a: Holding surface 42: Table base, 44: Rotation axis, 46: Frame body, 48: Porous plate A1, A2, A3, A4: Arrows S10: First cutting process, S20: Second cutting process, S30: Grinding process α, β: Angles

Claims

1. A method for processing a workpiece having a plate shape and including chamfered portions at outer peripheral portions on both sides, comprising: In the thickness direction of the workpiece whose first surface is held by the first holding surface of the first holding table, a first rotating shaft arranged along the first holding surface and located on the opposite side of and exposed from the first surface at the outer peripheral portion of the second surface. The tip of the first rotating shaft is arranged such that it does not intersect the extension line of the rotation center of the first table rotating shaft of the first holding table arranged orthogonally to the first holding surface on the extension line of the rotation center of the first rotating shaft. With a first cutting blade mounted thereon being in a cutting state, the first holding table is rotated around the first table rotating shaft, thereby forming a first stepped portion having a curved surface that is recessed from the second surface toward the first surface as it advances outward from the center of the second surface at the outer peripheral portion of the workpiece in a first cutting step; After the first cutting step, a second rotating shaft arranged along the second holding surface of the second holding table that holds the first surface of the workpiece. The tip of the second rotating shaft is arranged such that it intersects the extension line of the rotation center of the second table rotating shaft of the second holding table on the extension line of the rotation center of the second rotating shaft. With a second cutting blade mounted thereon being in a cutting state such that it does not contact the innermost circumference of the curved surface, the second holding table is rotated around the second table rotating shaft, thereby forming a second stepped portion at the outer peripheral portion of the workpiece in a second cutting step; A method for processing a workpiece, characterized by comprising the above steps.

2. The method for processing a workpiece according to claim 1, wherein in the second cutting step, the distance from the bottom surface of the second stepped portion to the first surface is made equal to or less than the distance from the lowermost end of the first stepped portion to the first surface.

3. The method for processing a workpiece according to claim 1, wherein in the second cutting step, the distance from the bottom surface of the second stepped portion to the first surface is made greater than the distance from the lowermost end of the first stepped portion to the first surface.

4. The method for processing a workpiece according to claim 1, wherein in the second cutting step, the first cutting blade used in the first cutting step is used as the second cutting blade, or in the second cutting step, a cutting blade having the same material, the same structure, and the same shape as the first cutting blade is used as the second cutting blade.

5. After the second cutting step, by grinding the first surface of the workpiece, a grinding step is further provided in which the thickness of the workpiece is made equal to or less than the distance from the bottom surface of the second stepped portion formed in the second cutting step to the first surface. The method for machining a workpiece according to any one of claims 1 to 4, characterized in that it further comprises this.

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