JP2012039039A - Processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method which can process a work piece of any shape by directly sucking and holding the work piece to a holding table.SOLUTION: A work piece 1 is placed on an adhesive sheet 5 glued to a holding surface 73 of a holding table 70, the adhesive sheet 5 is severed along the outer periphery of the work piece 1 in order to divide the adhesive sheet 5 into a part 5A which corresponds to a work piece corresponding region 73A of the holding surface 73 and a part 5B which corresponds to an outer region 73B. Then, the part 5A, which corresponds to the work piece corresponding region 73A, of the adhesive sheet 5 is removed in order to correspond the work piece 1 to the work piece corresponding region 73A and directly place the work piece 1 on the work piece corresponding region 73A. Further, the work piece 1 is sucked and held to the holding surface 73 to be processed.

Description

  The present invention relates to a processing method for performing processing such as grinding, polishing, and cutting on a workpiece such as a semiconductor wafer sucked and held by a holding table.

  In the semiconductor device manufacturing process, first, dividing lines are formed in a lattice shape on the surface of a wafer made of silicon, compound semiconductor, or the like, and then ICs or semiconductor devices are formed on a number of rectangular device regions partitioned by the dividing lines. A plurality of circuit elements such as LSIs are formed. After that, the back surface of the wafer is ground and polished by a grinding device or a polishing device and thinned to a predetermined thickness, and then cut along a predetermined division line by a cutting device and divided into individual device regions. Are performed, and a large number of devices (semiconductor chips) are manufactured from one wafer.

  By the way, in recent years, as a technique for realizing lighter, thinner, and smaller semiconductor devices, a plurality of metal protrusions called bumps are formed on the device surface, and a flip is performed in which these bumps are directly bonded to the electrodes formed on the wiring board. A mounting method called chip bonding has been put into practical use. Since the bumps are formed by a method such as plating or stud bumps, the height positions of the individual bumps are not uniform, and it is difficult to uniformly bond the plurality of bumps to the electrodes of the wiring board as they are.

  In view of this, a cutting apparatus has been proposed for cutting the tip of the bump with a cutting tool so as to make the height position uniform (see Patent Document 1). Various processing devices including such a cutting tool (including a grinding device, a polishing device, and a cutting device using a cutting blade) usually have a vacuum chuck type holding table that sucks and holds a workpiece by negative pressure action, And processing means for processing the workpiece held by the holding table. And when holding a work piece with a holding table, for the purpose of improving the handleability of the work piece and the like, an adhesive sheet is stuck to the work piece on the surface opposite to the work surface. There is a case. The workpiece to which the adhesive sheet is attached is sucked and held by the holding table through the adhesive sheet so that the processing surface is exposed.

  On the other hand, if high accuracy is required for the flatness of the work surface by grinding or polishing, the cutting depth of the cutting to the work surface, or the cutting height position by bite cutting, an adhesive sheet is attached to the work piece. When sticking, the inconvenience that high-precision processing cannot be performed due to variations in the thickness of the pressure-sensitive adhesive sheet occurs. Therefore, in such a case, a method is adopted in which the workpiece is directly placed on the holding table and sucked and held, and the workpiece is processed in that state. The holding table when the workpiece is directly placed has a suction area in which a number of suction holes for sucking air are exposed on the surface in a shape corresponding to the outer shape of the workpiece. The outer shape is placed in conformity with the suction area. As a result, the workpiece is sucked and held on the holding table with a sufficient negative pressure without air leakage.

JP 2010-36300 A

  The outer shape of the wafer made of silicon is circular, but the outer shape of the workpiece is not limited to such a circular shape. Therefore, in order to process a workpiece having various outer shapes by directly sucking and holding the workpiece with the holding table, a plurality of holding tables having suction areas corresponding to the outer shape of the workpiece are required. However, when a plurality of holding tables corresponding to the outer shape of the workpiece are prepared, it takes time to replace the holding table every time a workpiece having a different outer shape is processed, and it is necessary to manage the plurality of holding tables. There is a burden on the operator.

Further, wafers that are easily damaged, such as wafers made of gallium arsenide (GaAs) or gallium phosphide (GaP), and expensive wafers such as wafers made of sapphire (Al ₂ O ₃ ) or gallium nitride (GaN), Even those that are damaged and become irregularly shaped may be processed. However, it is practically impossible to create a holding table having a suction area corresponding to the outer shape of the damaged wafer. Therefore, these irregular wafers are directly sucked and held on the holding table without using an adhesive sheet. It was difficult to do.

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a processing method capable of processing a workpiece having any outer shape by directly sucking and holding the workpiece on a holding table.

  The processing method of the present invention is a processing method for processing a workpiece sucked and held by a holding table, wherein the pressure-sensitive adhesive sheet is attached to the holding surface of a holding table having a holding surface for holding the workpiece. Workpiece-corresponding region corresponding to the work piece on the holding surface by cutting the adhesive sheet attached to the holding surface and the outer edge of the work piece to be processed. And an adhesive sheet separating step for separating the portion corresponding to the outer region that is outside the outer edge of the workpiece on the holding surface, and the portion corresponding to the separated workpiece corresponding region A pressure-sensitive adhesive sheet removing step for removing the pressure-sensitive adhesive sheet from the holding surface, and placing the workpiece in correspondence with the workpiece-corresponding region on the holding surface, and sucking and holding the workpiece by the holding table To be processed A holding step, characterized in that it comprises a processing step of performing processing by the processing means to the workpiece is suction-held by the holding table.

  According to the present invention, the workpiece is placed directly on the workpiece corresponding region on the holding surface of the holding table, and the outer region around the workpiece on the holding surface is covered with the adhered adhesive sheet. The entire holding surface is covered with a workpiece or an adhesive sheet. For this reason, air leakage does not occur on the holding surface and a sufficient negative pressure action occurs, and the workpiece is sucked and held by the holding surface with a sufficient suction force. In the present invention, in the pressure-sensitive adhesive sheet separating step, the pressure-sensitive adhesive sheet corresponds to a part corresponding to the workpiece corresponding region on the holding surface and an outer region which is outside the outer edge of the workpiece on the holding surface. Any outer shape of the workpiece can be processed by placing the workpiece in correspondence with the workpiece corresponding area on the holding surface from which the adhesive sheet of the portion corresponding to the workpiece corresponding area is removed. Even with an object, the workpiece can be placed on the holding surface without exposing the holding surface and causing air leakage.

  In the present invention, the processing means includes a grinding wheel or a cutting tool. Thus, in a form in which the processing means includes a grinding wheel or a cutting tool, the present invention removes the adhesive sheet in a portion corresponding to the outer region from the holding surface after performing the processing step. Including a planarizing step of planarizing the holding surface by grinding or cutting with a means. By performing this flattening step, if a scratch or the like is generated on the holding surface in the pressure-sensitive adhesive sheet separating step, the scratch or the like can be removed.

The workpiece to be referred to in the present invention is not particularly limited. For example, as the workpiece to be processed by a grinding apparatus or a polishing apparatus, the above-described silicon, gallium arsenide (GaAs), gallium phosphide (GaP), sapphire (Al ₂ O ₃ ), In addition to gallium nitride (GaN), various wafers and substrates made of ceramic, glass, etc., ductile materials of plate metal and resin, flatness on the order of micron to submicron (TTV: total thickness variation) Examples include various processing materials that require a difference between the maximum value and the minimum value of the entire surface to be ground of the workpiece measured in the thickness direction with respect to the ground surface.

Also, for example, various semiconductor wafers, adhesive members such as DAF (Die Attach Film) provided on the back side of the wafer for chip mounting, semiconductor product packages, ceramics as workpieces to be processed by a cutting device for dicing the workpiece Glass, sapphire (Al ₂ O ₃ ) -based inorganic material substrates, various electronic components such as LCD drivers for controlling and driving liquid crystal display devices, and various processing materials that require micron-order processing position accuracy. Furthermore, various semiconductor wafers etc. in which a plurality of the bumps are formed and the bumps are cut by a cutting tool to make the height position uniform.

  According to the present invention, it is possible to provide a processing method capable of processing a workpiece having any outer shape by directly sucking and holding the workpiece on the holding table.

1 is a perspective view of a cutting tool for cutting a bump of a workpiece by applying a processing method according to an embodiment of the present invention. It is the (a) top view of the holding table which a cutting tool has, (b) The top view of the state where the adhesive sheet was stuck on the surface of the holding table. It is a side view which shows the adhesive sheet sticking process of one Embodiment. It is a top view which shows the adhesive sheet isolation | separation process of one Embodiment, Comprising: (a) The state which mounted the workpiece on the adhesive sheet on a holding table, (b) An adhesive sheet along the outer periphery of a workpiece The state which cut | disconnected and removed the to-be-processed object is shown. It is a side view which shows the adhesive sheet separation process of one Embodiment. It is a top view which shows the adhesive sheet removal process of one Embodiment. It is a top view which shows the state which mounted the workpiece in the workpiece corresponding area | region of the holding surface of a holding table. It is a side view of the state of FIG. It is a side view which shows the manufacturing process of one Embodiment. It is a partially expanded side view of a workpiece, (a) Before cutting of bump, (b) After cutting of bump. It is a side view which shows the planarization process of one Embodiment.

Hereinafter, an embodiment in which the present invention is applied to the bump cutting will be described with reference to the drawings.
FIG. 1 shows a cutting tool 10 suitable for cutting a bump. First, the configuration of the cutting tool 10 will be described.

[1] Configuration of Tool Cutting Device Reference numeral 11 in FIG. A wall 12 is erected on one end in the longitudinal direction of the device base 11 (the end on the far side in FIG. 1). In FIG. 1, the longitudinal direction, the width direction, and the vertical direction of the apparatus base 11 are set as a Y direction, an X direction, and a Z direction, respectively.

  On the apparatus base 11, the wall 12 side from the substantially middle part in the longitudinal direction is a machining area 11A, and the opposite side is to carry the workpiece before machining into the machining area 11A and to carry out the workpiece after machining. The loading / unloading area 11B is set.

(A) Mechanism of processing area A rectangular recess 13 is formed in the processing area 11A, and a vacuum chuck type disc-shaped holding table 70 is provided in the recess 13 via a movable table 14. Is movably provided in the Y direction. The moving table 14 is slidably attached to a guide rail that extends in the Y direction and is arranged in the apparatus table 11, and is reciprocated in the Y direction by a moving mechanism (both not shown).

  One end of the bellows 15, 16 is attached to both ends of the moving table 14 in the moving direction, and the other end of the bellows 15, 16 is the recess facing the inner surface of the wall portion 12 and the wall portion 12. Each is attached to the inner wall surface of 13. These bellows 15, 16 cover the moving path of the moving table 14 and prevent cutting chips and the like from falling on the moving path, and expand and contract as the moving table 14 moves.

  As shown in FIGS. 2A and 3, the holding table 70 includes a disc-shaped frame 71 made of stainless steel and the like, and a porous portion 72 having countless pores inside. A circular recess 71b is formed concentrically on most of the upper surface of the frame 71, leaving the outer peripheral edge 71a, and a disc-shaped porous portion 72 is fitted into the recess 71b. Yes. The upper surface of the porous portion 72 is horizontal and flush with the upper surface of the outer peripheral edge portion 71a of the frame 71, and the circular upper surface of the porous portion 72 holds the work piece by suction. It is configured as. Note that the holding surface 73 of the holding table 70 may be configured by forming a large number of air suction holes in addition to those formed by the porous portion 22.

  The holding table 70 is positioned at a predetermined processing position when the movable table 14 moves to the wall 12 side. A cutting means (processing means) 20 is arranged above the processing position as shown in FIG. The cutting means 20 is attached to the wall portion 12 of the apparatus base 11 through a slider 32 and a guide rail 31 so as to be lifted and lowered by the feed mechanism 30. The feed mechanism 30 is configured to rotate a ball screw 33 screwed and connected to a slider 32 with a motor 34, and the rotation of the ball screw 33 drives the slider 32 up and down.

  The cutting means 20 includes a cylindrical spindle housing 22 whose axial direction extends in the Z direction, a spindle shaft 23 that is coaxially and rotatably supported in the spindle housing 22, and a servo motor 24 that rotationally drives the spindle shaft 23. And a disc-shaped wheel mount 25 coaxially fixed to the lower end of the spindle shaft 23, and a cutting tool 26 detachably attached to the wheel mount 25.

  The cutting means 20 moves up and down integrally with the slider 32 by fixing the spindle housing 22 to the slider 32 via the holder 34. The wheel mount 25 is rotated in the direction of the arrow (described on the upper surface of the wheel mount 25) in FIG. The cutting tool 26 has a blade portion made of diamond or the like for cutting a workpiece at the lower end.

(B) Mechanism of carry-in / carry-out area As shown in FIG. 1, a rectangular recess 18 is formed in the carry-in / carry-out area 11B. A pickup mechanism 60 having a fork 60b attached to the tip of a node link type horizontal turning arm 60a is installed.

  Then, around the recess 18, as viewed from above, the cassette 61, the alignment table 62, the carry-in arm 63 with the suction pad 63 b attached to the tip of the horizontal swivel arm 63 a, and the carry-in arm 63, a carry-out arm 64 having a horizontal turning arm 64a and a suction pad 64b, a spinner-type cleaning device 65, and a cassette 66 are arranged.

  The cassette 61, the alignment table 62, and the carry-in arm 63 are means of a system for carrying the workpiece into the holding table 70, and the carry-out arm 64, the cleaning device 65, and the cassette 66 hold the processed workpiece after the holding table. It is a means of the system which carries out from 70. Although the two cassettes 61 and 66 have the same structure, they are referred to as a carry-in cassette 61 and a carry-out cassette 66 according to applications. These cassettes 61 and 66 can accommodate and transport a plurality of workpieces, and are set at predetermined positions on the apparatus base 11.

  In the carry-in cassette 61, a plurality of workpieces before processing are accommodated in a stacked state. The pickup mechanism 60 takes out one workpiece from the carry-in cassette 61 by raising / lowering and turning the arm 60a and gripping the fork 60b, and further raises the workpiece on the workpiece surface on which bumps are formed. And has a function of being placed on the alignment table 62 in a state of being directed to.

  The workpiece placed on the alignment table 62 is positioned at a certain carry-in position. The carry-in arm 63 sucks the workpiece on the alignment table 62 onto the suction pad 63b, turns the arm 63a, places the workpiece on the holding table 70, and lowers the horizontal turning arm 63a. The function of placing the workpiece on the holding table 70 is provided by stopping the suction operation.

  The carry-out arm 64 has a function of sucking the processed workpiece onto the suction pad 64b from the holding table 70 and turning the arm 64a to transfer the workpiece into the cleaning device 65. The cleaning device 65 has a function of rotating the workpiece after the workpiece is washed with water and removing the water by shaking off the workpiece. The workpiece cleaned by the cleaning device 65 is transferred and accommodated in the unloading cassette 66 by the pickup mechanism 60.

  When the work piece is attached to or detached from the holding table 70 by the carry-in arm 63 and the carry-out arm 64, the movable table 14 is moved to the carry-in / carry-out area 11B side and stopped at a predetermined carry-in / carry-out position.

  The processing position of the workpiece by the cutting means 20 is a range moved by a predetermined distance from the loading / unloading position to the wall 12 side. You can go back and forth between locations.

[2] Processing Method Next, using the bump processing apparatus 10 having the above-described configuration, a method for cutting the tips of the bumps having a plurality of bumps formed on the surface thereof to uniformly align the height positions. Will be explained.

  The operator sets a carry-in cassette 61 that accommodates a plurality of workpieces and an empty carry-out cassette 66 at predetermined positions in the carry-in / carry-out area 11B. The code | symbol 1 of FIG. 4 has shown the example of the workpiece in this embodiment. The workpiece 1 is in the form of a thin plate such as a semiconductor wafer, and the original shape is an indefinite shape or an indeterminate shape due to breakage. A plurality of bumps 2 having different height positions are formed on the surface of the workpiece 1 as shown in FIG. In this case, the surface of the workpiece 1 is filled with an underfill material 3 that covers the bumps 2.

  Moreover, as shown in FIG.2 (b) and FIG. 3, the operator sticks the adhesive sheet 5 on the whole upper surface including the holding surface 73 of the holding table 70 (adhesive sheet sticking process). As the pressure-sensitive adhesive sheet 5, for example, a dicing tape that is attached to the back surface of the semiconductor wafer when dicing the semiconductor wafer is suitably used. Incidentally, the dicing tape has a configuration in which, for example, a resin adhesive having a thickness of about 5 μm is applied to one surface of a base material made of polyvinyl chloride having a thickness of about 100 μm. For example, as shown in FIG. 3, the pressure-sensitive adhesive sheet 5 is adhered to the holding surface 73 by rolling the roller 9 against the pressure-sensitive adhesive sheet 5 in the arrow direction on the holding surface 73.

  Subsequently, a single workpiece is taken out from the carry-in cassette 61 by the pickup mechanism 60, placed on the alignment table 62, and positioned at a predetermined carry-in position. Next, the workpiece on the alignment table 62 is placed by the loading arm 63 on the holding surface 73 of the holding table 70 positioned at the loading / unloading position via the adhesive sheet 5. The workpiece 1 is placed on the holding surface 73 with the surface on which the bumps 2 are formed facing upward.

  When the workpiece 1 is placed on the holding surface 73 of the holding table 70 via the adhesive sheet 5, the operator attaches the adhesive sheet 5 to the workpiece 1 as shown in FIGS. Cut along the outer edge. As a result, as shown in FIG. 5, the holding surface 73 is partitioned into a workpiece corresponding area 73 </ b> A corresponding to the workpiece 1 and an outer area 73 </ b> B corresponding to the outside of the outer edge of the workpiece 1. The adhesive sheet 5 is separated into a part 5A corresponding to the workpiece corresponding area 73A and a part 5B corresponding to the outer area 73B (adhesive sheet separating step). In this way, the adhesive sheet 5 can be cut by moving the cutter 80 cut into the adhesive sheet 5 along the outer edge of the workpiece 1 as shown in FIG.

  Next, as shown in FIG. 6, the part 5A corresponding to the workpiece corresponding region 73A of the separated adhesive sheet 5 is peeled off from the workpiece corresponding region 73A of the holding surface 73 as indicated by an arrow (adhesive). Sheet removal step). As a result, a hole having the shape of the workpiece 1 is formed in the adhesive sheet 5, and the workpiece corresponding area 73 </ b> A of the holding surface 73 is exposed in the hole. Next, as shown in FIGS. 7 and 8, the work piece 1 is made to exactly correspond to the hole, that is, the work piece corresponding area 73 </ b> A, and the back surface side of the work piece 1 where the bump 2 is not formed is held on the holding surface 73. Place directly according to the.

  Subsequently, the vacuum operation of the holding table 70 is started, and the workpiece 1 is directly sucked and held in the workpiece corresponding area 73A of the holding surface 73 (workpiece holding step). The operator may perform the placement of the workpiece 1 on the adhesive sheet 5 adhered to the holding surface 73 and the placement of the workpiece 1 in the workpiece corresponding area 73A. You may carry out by the carrying-in arm 63.

  Thus, the workpiece 1 is sucked and held on the holding table 70, and the cutting (processing step) of the bump 2 of the workpiece 1 is performed as follows.

  The vertical position of the cutting means 20 is adjusted by the feed mechanism 30 so that the cutting tool 26 can cut the bump 2 to a predetermined height, and the wheel mount 25 is rotated by the servo motor 24. From this state, the work table 1 held on the holding table 70 is cut at a predetermined speed by moving the holding table 70 in the direction of arrow Y1 (in the direction of the wall 12) via the moving table 14 as shown in FIG. It is fed to the machining position below the means 20, that is, below the rotating tool 26 as shown by the arrow R. Thereby, as shown in FIG. 10B, the tip of the bump 2 is cut by the blade portion of the cutting tool 26 and the height position is aligned.

  When the tips of all the bumps 2 are cut and the height positions are aligned, the operation of the cutting means 20 is stopped and retracted upward. Thereafter, the holding table 70 is moved to the loading / unloading position, the vacuum operation is stopped, and the suction holding of the workpiece 1 is released. Next, the workpiece 1 is picked up from the holding table 70 by the carry-out arm 64, transferred into the cleaning device 65, and washed with water and dried in the cleaning device 65. Then, it is transferred and accommodated in the carry-out cassette 66 by the pickup mechanism 60.

  The above is a cycle in which the tip of the bump 2 is cut with respect to one workpiece 1 and then washed and collected, and this cycle is repeated. When all the workpieces in the carry-in cassette 61 have been processed, the workpiece is moved to the next step together with the carry-out cassette 66.

[3] Effect According to the processing method of the present embodiment, the workpiece 1 is placed directly on the workpiece corresponding area 73 </ b> A on the holding surface 73 of the holding table 70, and around the workpiece on the holding surface 73. The outer region 73 </ b> B is covered with the adhered adhesive sheet 5, so that the entire holding surface 73 is covered with the workpiece 1 or the adhesive sheet 5. Therefore, a sufficient negative pressure action is generated, and the workpiece 1 is sucked and held by the holding surface 73 with a sufficient suction force.

  In this processing method, the pressure-sensitive adhesive sheet 5 is cut along the outer edge of the workpiece 1 in the pressure-sensitive adhesive sheet separating step so that the pressure-sensitive adhesive sheet 5 corresponds to the workpiece 1 on the holding surface 73. The portion 5A corresponding to the region 73A and the portion 5B corresponding to the outer region 73B outside the outer edge of the workpiece 1 on the holding surface 73 are separated, and then into the workpiece corresponding region 73A of the adhesive sheet 5 By placing the workpiece 1 in a corresponding manner on the workpiece corresponding region 73A from which the corresponding portion 5A has been removed, the holding surface of the workpiece of any outer shape is exposed, leading to air leakage. The workpiece can be placed on the holding surface without any problem.

  In addition, in order to cut | disconnect the adhesive sheet 5 along the external shape edge of the to-be-processed object 1 at an adhesive sheet isolation | separation process, if there exists an appropriate method besides the method of using the cutter 80 as mentioned above, the method will be employ | adopted. be able to. When the cutter 80 is used as in the present embodiment, a groove-like scratch may remain on the holding surface 73 due to the tip of the cut cutter 80. If such a scratch remains on the holding surface 73, the suction holding function may be hindered. In this embodiment, as shown in FIG. 11, the holding is performed in the same manner as when the workpiece 1 is processed. The table 70 is moved in the direction of the arrow Y1, and self-cutting is performed in which the entire holding surface 73 is cut by the cutting tool 20 rotating as indicated by the arrow R to flatten the holding surface 73 (flattening step). Thereby, in this embodiment, the damage | wound by the cutter 80 made on the holding surface 73 can be removed promptly and easily.

[4] Other Embodiments of the Invention In addition to the machining method of cutting the bumps 2 of the workpiece 1 with the cutting tool 26 as in the above embodiment, the present invention can grind or polish any workpiece or The present invention can also be applied to various processes such as dicing that cuts a workpiece into a plurality of parts. In cutting or grinding with a cutting tool, scratches on the holding surface of the holding table can be removed by self-cutting as described above, but self-cutting is not possible in the case of polishing or dicing. It is good to grind and flatten with a grindstone such as an oil grindstone.

DESCRIPTION OF SYMBOLS 1 ... Workpiece 5 ... Adhesive sheet 5A ... The part corresponding to the workpiece corresponding area | region of an adhesive sheet 5B ... The part 20 corresponding to the outer side area | region of an adhesive sheet ... Cutting means (processing means)
26 ... Bite (cutting bite)
70 ... Holding table 73 ... Holding surface 73A ... Workpiece corresponding region 73B on holding surface ... Outside region of holding surface

Claims (3)

A processing method for processing a workpiece sucked and held by a holding table,
An adhesive sheet attaching step of attaching an adhesive sheet to the holding surface of the holding table having a holding surface for holding the workpiece;
The adhesive sheet attached to the holding surface is cut along the outer edge of the workpiece to be processed, and the portion corresponding to the workpiece corresponding region corresponding to the workpiece on the holding surface; A pressure-sensitive adhesive sheet separating step for separating the holding surface into a portion corresponding to an outer region that is outside the outer edge of the workpiece;
A pressure-sensitive adhesive sheet removing step for removing the part of the pressure-sensitive adhesive sheet corresponding to the separated workpiece-corresponding region from the holding surface;
A workpiece holding step of placing the workpiece in correspondence with the workpiece corresponding region on the holding surface and sucking and holding the workpiece by the holding table;
A processing step of processing the workpiece sucked and held by the holding table with a processing means;
A processing method characterized by comprising:   The processing method according to claim 1, wherein the processing means includes a grinding wheel or a cutting tool.   After performing the processing step, the method has a flattening step of removing a portion of the adhesive sheet corresponding to the outer region from the holding surface and flattening the holding surface by grinding or cutting with the processing means. The processing method according to claim 2.

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