Correction method and grinding method for workpiece

Abstract

To suppress a grinding stone that constitutes a ground region from vibrating during grinding of a work-piece.SOLUTION: A correction method, which corrects shapes of an inner peripheral surface side and an outer peripheral surface side of a plurality of grinding stones of a grinding wheel, comprises: a holding step of suction-holding a dressing board with a chuck table; a correcting step of rotating the grinding wheel around a second rotary shaft around which the grinding wheel is rotated in a state where at least one grinding stone is inserted into a groove part in a circular arc shape formed in a dressing part, and further rotating the chuck table around a first rotary shaft, so as to correct the shapes of the inner peripheral surface side and the outer peripheral surface side of the plurality of grinding stones so that deviations of the second rotary shaft from centers of annular grinding surfaces defined on lower surface of the plurality of grinding stones are reduced, utilizing a first side surface of the groove part opposing to the inner peripheral surfaces of the plurality of grinding stones and a second side surface of the groove part opposing to the outer peripheral surfaces of the plurality of grinding stones; and a separating step of separating the plurality of grinding stones from the dressing part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a correction method for correcting the shapes of the inner and outer peripheral surfaces of a plurality of grinding wheels, and a grinding method for a workpiece for grinding a predetermined area on the back surface of the workpiece that corresponds to a device area on the front surface of the workpiece. [Background technology]

[0002] In the manufacturing process of semiconductor device chips, a plurality of planned dividing lines (streets) are set in a grid pattern on the surface, and a wafer (i.e., workpiece) on which devices such as ICs (Integrated Circuits) are formed is processed in each area partitioned by the plurality of streets.

[0003] For example, the back side of the workpiece is ground with a grinding device to thin it, and then the workpiece is cut along each street with a cutting device, thereby dividing the workpiece into multiple semiconductor device chips.

[0004] The grinding device used for this grinding includes a grinding unit including a cylindrical spindle. An annular grinding wheel is attached to the lower end of the spindle via a disk-shaped mount. The grinding wheel has an annular wheel base.

[0005] On one side of the wheel base, for example, a plurality of segment-shaped grinding wheels are arranged at approximately equal intervals along the circumferential direction of the wheel base. Each grinding wheel has abrasive grains and a bond material for fixing the abrasive grains.

[0006] In an unused grinding wheel, the abrasive grains do not properly protrude from the bond material. Therefore, before grinding a workpiece, the bottom side of the grinding wheel is dressed using a dressing board to properly protrude the abrasive grains from the bond material (see, for example, Patent Document 1).

[0007] Incidentally, apart from the appropriate protrusion of abrasive grains from the bond material due to dressing, another factor that determines the quality of the grinding process is the runout within the plane of the grinding wheel when the grinding wheel is rotated around the spindle as the rotation axis.

[0008] For example, if the center of a specified circle on which multiple grinding wheels are arranged does not coincide with the radial center of the wheel base, when the grinding wheel is rotated around the spindle as the rotation axis, the grinding wheels that make up the grinding area will vibrate in a horizontal plane. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-221360 Summary of the Invention [Problem to be solved by the invention]

[0010] If the grinding wheel constituting the grinding area vibrates within a plane when grinding a workpiece, this may lead to processing defects such as an increase in the number of chips on the outer periphery of the workpiece.

[0011] The present invention has been made in view of the above problems, and has an object to suppress runout of a grinding wheel that constitutes a grinding area when a workpiece is ground. [Means for solving the problem]

[0012] According to one aspect of the present invention, a method for correcting the shapes of the inner and outer peripheral surfaces of a grinding wheel having a plurality of grinding wheels arranged in a ring includes a holding step in which a lower surface of a support base of a dressing board having a dressing part fixed to the upper surface of the support base is suction-held by a holding surface of a chuck table; after the holding step, the grinding wheel is rotated around a second rotation axis that rotates the grinding wheel with at least one grinding wheel of the plurality of grinding wheels inserted into an arc-shaped groove formed in the dressing part; and further, the chuck table is rotated around a first rotation axis. The correction method includes a correction step of correcting the shapes of the inner and outer peripheral surfaces of the grinding wheels by rotating them around a rotation axis, using a first side surface of the groove portion facing the inner peripheral surface of the grinding wheels and a second side surface of the groove portion facing the outer peripheral surface of the grinding wheels, so that the deviation between the second rotation axis and the center of the annular grinding surface defined by the undersides of the grinding wheels becomes small, and a separation step of separating the grinding wheels from the dressing part by moving the chuck table and the grinding wheel relatively apart along the extension direction of the second rotation axis after the correction step.

[0013] Preferably, the correction method further includes a groove forming step of forming the groove in the dressing portion after the holding step and before the correction step by bringing the chuck table and the grinding wheel relatively close together along the extension direction of the second rotation axis while the chuck table is not rotated and the grinding wheel is rotated around the second rotation axis.

[0014] Preferably, the dressing board that is suction-held by the holding surface in the holding step has an arc-shaped groove portion formed in the dressing portion, the groove portion having a width greater than the blade width of the grinding wheel.

[0015] According to another aspect of the present invention, there is provided a method for grinding a workpiece, the workpiece having a device region on its front surface where a plurality of devices are formed and an outer peripheral excess region surrounding the device region, for grinding a predetermined region on the back surface of the workpiece corresponding to the device region, the method comprising: a shape modifying step of modifying the shapes of inner and outer peripheral surfaces of a grinding wheel having a plurality of grinding stones arranged in an annular manner; and after the shape modifying step, rotating a chuck table around a first rotation axis and rotating the grinding wheel around a second rotation axis, and and a grinding step of grinding the predetermined area of ​​the workpiece with the grinding wheel by bringing the cable and the grinding wheel relatively close to each other along the extension direction of the second rotation axis, wherein the shape modification step includes a holding step of suction-holding the lower surface of a support base of a dressing board having a dressing part fixed to the upper surface of the support base with a holding surface of the chuck table, and after the holding step, moving the chuck table and the grinding wheel along the second rotation axis without rotating the chuck table and in a state where the grinding wheel is rotated around the second rotation axis. a groove forming step of forming a groove in the dressing portion by bringing the grinding wheels closer to each other; and after the groove forming step, rotating the grinding wheel around the second rotation axis with at least one grinding wheel among the plurality of grinding wheels inserted into the arc-shaped groove formed in the dressing portion, and further rotating the chuck table around the first rotation axis to form a groove between the second rotation axis and the lower surfaces of the plurality of grinding wheels by utilizing a first side surface of the groove facing the inner peripheral surfaces of the plurality of grinding wheels and a second side surface of the groove facing the outer peripheral surfaces of the plurality of grinding wheels. a correcting step of correcting the shapes of the inner peripheral surface side and the outer peripheral surface side of the plurality of grinding wheels so that a deviation from the center of a predetermined annular grinding surface becomes small; and a separating step of separating the plurality of grinding wheels from the dressing part by relatively separating the chuck table and the grinding wheel along an extending direction of the second rotation axis after the correcting step, wherein the grinding step includes a workpiece holding step of holding the front surface side of the workpiece with the holding surface; and after the workpiece holding step, grinding the predetermined area on the back surface side of the workpiece corresponding to the device area with the grinding wheel;and a recess forming step of forming a disk-shaped thinned portion and a ring-shaped reinforcing portion surrounding the thinned portion. [Effects of the Invention]

[0016] In one embodiment of the correction method of the present invention, by rotating a chuck table with multiple grinding wheels inserted into arc-shaped grooves formed in a dressing section, the shapes of the inner and outer peripheral surfaces of the multiple grinding wheels are corrected using a first side of the grooves facing the inner peripheral surfaces of the multiple grinding wheels and a second side of the grooves facing the outer peripheral surfaces of the multiple grinding wheels.

[0017] This reduces the deviation between the center of rotation of the grinding wheel and the center of the annular grinding surface defined by the undersides of multiple grinding stones, thereby suppressing the vibration of the grinding stones that make up the grinding area when grinding the workpiece. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a flow diagram of a correction method. [Figure 2] FIG. 2 is a partial cross-sectional side view of the grinding device. [Figure 3] Figure 3(A) is a top view of the workpiece during grinding, Figure 3(B) is a top view of the grinding wheel shown in Figure 3(A) when rotated 90 degrees, Figure 3(C) is a top view of the grinding wheel shown in Figure 3(B) when rotated 90 degrees, and Figure 3(D) is a top view of the grinding wheel shown in Figure 3(C) when rotated 90 degrees. [Figure 4] FIG. 10 is a partial cross-sectional side view showing a holding step. [Figure 5] FIG. 10 is a partial cross-sectional side view after the holding step and before the groove forming step. [Figure 6] FIG. 10 is a top view after the holding step and before the groove forming step. [Figure 7] FIG. 10 is a partial cross-sectional side view showing a groove forming step. [Figure 8] FIG. 10 is a top view showing a groove forming step. [Figure 9]FIG. 10 is a partial cross-sectional side view showing a repair step. [Figure 10] FIG. 10 is a top view showing a repair step. [Figure 11] FIG. 10 is a partial cross-sectional side view showing the separation step. [Figure 12] FIG. 12(A) is a top view showing a dressing board according to a modified example, and FIG. 12(B) is a top view showing a correction step according to the modified example. [Figure 13] FIG. 6 is a partial cross-sectional side view of a grinding device according to a second embodiment. [Figure 14] Figure 14(A) is an oblique view of a workpiece, Figure 14(B) is a cross-sectional view of the workpiece after grinding in the second embodiment, and Figure 14(C) is a cross-sectional view of the workpiece after grinding in the comparative example. [Figure 15] FIG. 1 is a flow diagram of a method for grinding a workpiece. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a flow diagram of a correction method for correcting the shapes of a plurality of grinding wheels 58 (see Fig. 2) according to a first embodiment. In the first embodiment, the steps are performed in the following order: a holding step S10, a groove forming step S20, a correction step S30, and a separation step S40.

[0020] First, we will explain the grinding device 2 used in this correction method. Figure 2 is a partial cross-sectional side view of the grinding device 2. Note that the +Z direction and -Z direction shown in Figure 2 are directions parallel to the Z-axis direction and opposite to each other. For example, the Z-axis direction is the vertical direction, the +Z direction is the upward direction, and the -Z direction is the downward direction.

[0021] The +X and -X directions are opposite directions parallel to the X-axis direction, which is orthogonal to the Z-axis direction, and the +Y and -Y directions are opposite directions parallel to the Y-axis direction, which is orthogonal to the Z-axis direction and the X-axis direction. For example, the XY plane corresponds to the horizontal plane.

[0022] The grinding device 2 has a base 4 that supports each of the components. A pair of guide rails 6, each arranged along the X-axis direction, is provided on the upper surface of the base 4. A movable plate 8, which is rectangular in plan view, is slidably attached to the pair of guide rails 6.

[0023] A nut portion 10 is provided on the underside of the moving plate 8. A screw shaft 12, which is arranged substantially parallel to the X-axis direction, is rotatably connected to the nut portion 10 using balls (not shown). A motor 14 is connected to one end of the screw shaft 12.

[0024] When the screw shaft 12 is rotated by the motor 14, the moving plate 8 moves along the X-axis direction. The pair of guide rails 6, the moving plate 8, the screw shaft 12, the motor 14, etc. constitute an X-axis direction moving mechanism 16.

[0025] A disk-shaped chuck table 18 is supported on the upper surface of the movable plate 8. The chuck table 18 has a disk-shaped frame body 20 made of ceramics. A disk-shaped recess having a predetermined depth is formed in the center of the frame body 20.

[0026] A tube, a groove, and the like (not shown) connected to a suction source (not shown) such as a vacuum pump are formed in the frame 20. A disk-shaped porous plate 22 made of porous ceramics and having approximately the same diameter as the inner diameter of the recess is fixed to the recess.

[0027] When negative pressure is transmitted from the suction source to the tube, groove, etc., negative pressure is generated on the upper surface of the porous plate 22. The upper surface of the frame 20 and the upper surface of the porous plate 22 form a holding surface 18a that is approximately flush with each other. The holding surface 18a has a conical shape with the center protruding slightly compared to the outer periphery.

[0028] On the holding surface 18a, a disk-shaped workpiece 21 (see FIG. 3(A)) or a disk-shaped dressing board 11 (see FIG. 4) is respectively sucked and held by using negative pressure. Here, the dressing board 11 will be described with reference to FIG. 4.

[0029] The dressing board 11 is used when truing and / or dressing a plurality of grinding wheels 58 (described later) The dressing board 11 has a disk-shaped support base 13 made of resin.

[0030] The support base 13 has a predetermined diameter that is equal to or larger than the diameter of the upper surface of the porous plate 22 and equal to or smaller than the diameter of the upper surface of the frame 20. On the upper surface 13a of the support base 13, a disk-shaped dressing part 15 having a smaller diameter than the support base 13 is arranged substantially concentrically with the support base 13.

[0031] The dressing part 15 has a thickness of, for example, 10 mm, and is fixed to the upper surface 13a of the support base 13 by an adhesive or the like. The dressing part 15 has abrasive grains such as white alundum (WA) or green carbon (GC) and a bonding material such as a vitrified bond or a resin bond for fixing the abrasive grains.

[0032] The abrasive grains of the dressing portion 15 have a predetermined grain size indicated by the symbol # and a numerical value. The grain size conforms to the grain size distribution of fine powder in the sedimentation test method or electrical resistance test method of JIS (Japanese Industrial Standards) R 6001-2.

[0033] The dressing portion 15 of this embodiment is used to perform truing on the grinding wheel 58, and therefore has a larger average grain size of abrasive grains than a dressing portion intended only for dressing the grinding wheel 58.

[0034] Specifically, abrasive grains having an average grain size specified by #4000 or abrasive grains having an average grain size larger than the average grain size specified by #4000 are used as the abrasive grains of the dressing portion 15.

[0035] In the particle size notation, the smaller the number following the #, the larger the average particle size (for example, referred to as the median diameter or 50% diameter), and the larger the number following the #, the smaller the average particle size.

[0036] 2, the other components of the grinding device 2 will now be described. A rotating shaft (first rotating shaft) 24 is fixed to the lower part of the chuck table 18. A driven pulley (not shown) is connected to the rotating shaft 24.

[0037] A rotary drive source (not shown) such as a motor is provided on the moving plate 8, and an endless belt (not shown) is hung between a drive pulley (not shown) connected to the output shaft of this rotary drive source and a driven pulley fixed to the rotating shaft 24.

[0038] When the rotary drive source is operated, the chuck table 18 rotates around a rotation axis 24. The chuck table 18 is rotatably supported by an annular bearing 26. The bearing 26 is also supported by an annular table base 28.

[0039] Furthermore, on the underside of the table base 28, a fixed support mechanism 30a, a first movable support mechanism 30b, and a second movable support mechanism 30c are provided at approximately equal intervals along the circumferential direction of the table base 28.

[0040] The fixed support mechanism 30a has a fixed shaft portion of a predetermined length. The upper part of the fixed shaft portion is fixed to the table base 28, and the lower part of the fixed shaft portion is fixed to the moving plate 8. The fixed shaft portion does not expand or contract and has a constant length.

[0041] Each of the first movable support mechanism 30b and the second movable support mechanism 30c has a movable shaft portion with a male thread formed on the upper portion. The lower portion of the movable shaft portion is rotatably supported with respect to the moving plate 8. In addition, the upper portion of the movable shaft portion is rotatably connected to a screw hole formed in the lower portion of the table base 28.

[0042] The inclination of table base 28 is adjusted by adjusting the length of the movable shaft inserted into the screw hole according to the rotation direction of the movable shaft. By adjusting the inclination of table base 28, a portion of holding surface 18a located directly below grinding unit 46 becomes approximately parallel to the X-Y plane.

[0043] A wall 30 extending in the +Z direction from the upper surface of the base 4 is provided at the end of the base 4 in the +X direction. A grinding feed mechanism 32 is provided on one side of the wall 30. The grinding feed mechanism 32 has a pair of guide rails 34 arranged along the Z-axis direction. Note that only one of the guide rails 34 is shown in FIG. 2.

[0044] A moving block 36 is slidably attached to the guide rail 34. A nut portion 38 is provided on the rear side surface of the moving block 36. A screw shaft 40, which is arranged substantially parallel to the Z-axis direction, is rotatably connected to the nut portion 38 via a ball (not shown).

[0045] A motor 42 is connected to the upper end of the screw shaft 40. When the motor 42 rotates the screw shaft 40, the moving block 36 moves along the Z-axis direction. A grinding unit 46 is fixed to the moving block 36 via a fixture 44.

[0046] The grinding unit 46 has a cylindrical spindle housing 48 arranged along the Z-axis direction. A part of a cylindrical spindle (second rotation shaft) 50 is rotatably housed in the spindle housing 48. The spindle 50 is arranged along the Z-axis direction.

[0047] A rotation drive source (not shown), such as a motor, is provided on a portion of the upper side of the spindle 50. The lower end of the spindle 50 protrudes downward from the bottom of the spindle housing 48, and the center of the upper surface side of a disk-shaped mount 52 is fixed to this lower end.

[0048] The mount 52 has approximately the same diameter as the holding surface 18a. An annular grinding wheel 54 having approximately the same diameter as the mount 52 is attached to the underside of the mount 52. The grinding wheel 54 has an annular wheel base 56 made of metal such as an aluminum alloy.

[0049] A plurality of grinding wheels 58 are arranged in a ring shape at predetermined intervals along the circumferential direction of the wheel base 56 on the underside 56a of the wheel base 56 (see FIG. 3). Each grinding wheel 58 has abrasive grains such as diamond or cBN (cubic boron nitride) and a bonding material such as ceramic or resin that fixes the abrasive grains.

[0050] The inner peripheral surface 58a of each grinding wheel 58 is disposed along one curved cylindrical surface, and similarly, the outer peripheral surface 58b of each grinding wheel 58 is disposed along another curved cylindrical surface (see FIG. 6). The inner peripheral surface 58a and the outer peripheral surface 58b are disposed approximately coaxially. The lower surface 58c of each grinding wheel 58 defines the annular grinding surface 54a (see FIG. 7).

[0051] The lower surface 58c of the grinding wheel 58 (see FIGS. 5 and 7) protrudes a predetermined amount from the lower surface 56a of the wheel base 56, and this protrusion amount is called the segment height. The segment height of each grinding wheel 58 is set to, for example, 1.0 mm or more and 8.0 mm or less. The segment height of the grinding wheel 58 in this embodiment is 7.0 mm.

[0052] When the spindle 50 is rotated, the grinding wheel 54 rotates around the spindle 50 (see FIG. 7). A nozzle (not shown) is provided at the bottom of the grinding unit 46 to supply grinding water such as pure water to the processing point.

[0053] The grinding device 2 is provided with a control unit (not shown) that controls the operation of the X-axis direction moving mechanism 16, the rotational drive source of the chuck table 18, the first movable support mechanism 30b and the second movable support mechanism 30c, the grinding feed mechanism 32, the grinding unit 46, the nozzle, etc.

[0054] The control unit is composed of a computer having, for example, a processor (processing device) represented by a CPU (Central Processing Unit), a main memory device such as DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), or ROM (Read Only Memory), and an auxiliary memory device such as a flash memory, a hard disk drive, or a solid state drive.

[0055] The auxiliary storage device stores software including a predetermined program. The functions of the control unit are realized by operating the processor in accordance with this software. For example, when grinding the workpiece 21, the control unit operates the grinding device 2 in accordance with predetermined processing conditions.

[0056] Furthermore, before grinding the workpiece 21, the grinding wheel 58 is dressed using the dressing board 11 to allow the abrasive grains to appropriately protrude from the bond material. When dressing is performed, the lower surface 13b of the dressing board 11 is usually first held by suction with the holding surface 18a.

[0057] Next, the chuck table 18 is rotated around the rotation axis 24, and the grinding wheel 54 is rotated around the spindle 50, while the grinding unit 46 is fed downward at a predetermined speed for grinding. The lower surface 58c of the grinding wheel 58 comes into contact with the upper surface 15a of the dressing portion 15, thereby dressing the lower surface 58c of the grinding wheel 58.

[0058] Apart from the dressing of the grinding wheel 58, another factor that determines the quality of the grinding process is the runout of the grinding wheel 58 that constitutes the grinding area in the XY plane.

[0059] For example, as shown in Figures 3(A) to 3(D), the center 54a1 of the annular grinding surface 54a defined by the lower surfaces 58c of multiple grinding wheels 58 is misaligned with the rotation center 50a of the grinding wheel 54 in the X-Y plane, causing the grinding wheels 58 that make up the grinding area to vibrate in the X-Y plane.

[0060] In addition, in FIGS. 3(A) to 3(D), for convenience of explanation, the distance between the center 54a1 and the rotation center 50a is exaggerated, but in reality the distance between them is very small, at 300 μm or less.

[0061] Fig. 3(A) is a top view during grinding of the workpiece 21. Fig. 3(B) is a top view when the grinding wheel 54 shown in Fig. 3(A) is rotated 90 degrees clockwise when viewed from above, and Fig. 3(C) is a top view when the grinding wheel 54 shown in Fig. 3(B) is rotated 90 degrees clockwise when viewed from above.

[0062] Fig. 3(D) is a top view of the grinding wheel 54 shown in Fig. 3(C) rotated 90 degrees clockwise in top view. In Fig. 3(B) to Fig. 3(D), the position of the grinding stone 58 that constitutes the grinding area in Fig. 3(A) is indicated by a dashed line. Also, the chuck table 18 is omitted, and the rotation center 24a of the rotation shaft 24 is indicated by a black circle.

[0063] As shown in Figures 3(A) to 3(D), if the center 54a1 and the center of rotation 50a are misaligned, the grinding wheel 58 that constitutes the grinding area will vibrate in the X-Y plane as if swinging in a predetermined direction when grinding the workpiece 21.

[0064] The runout of the grinding wheel 58 that constitutes the grinding area may lead to processing defects such as an increase in the number of chippings on the outer periphery of the workpiece 21 (i.e., a decrease in the processing quality of the edge portion of the workpiece 21).

[0065] In addition, the centrifugal force acting on the grinding wheel 54 due to the misalignment of the center 54a1 and the center of rotation 50a may cause the spindle 50 to vibrate in the XY plane, which may lead to poor machining of the workpiece 21.

[0066] Therefore, in this embodiment, before grinding the workpiece 21, the shape of the grinding wheels 58 is corrected by truing the multiple grinding wheels 58 using the grinding device 2 and the dressing board 11 according to the flow shown in Figure 1.

[0067] 1 is executed by operating the grinding device 2 in accordance with a predetermined program stored in the auxiliary storage device. First, the X-axis direction moving mechanism 16 is operated to place the chuck table 18 at a carry-in / carry-out position away from the position of the grinding unit 46 in the -X direction.

[0068] 4, the lower surface 13b of the support base 13 is suction-held by the holding surface 18a so that the upper surface 15a of the dressing part 15 is exposed (holding step S10). FIG. 4 is a partial cross-sectional side view showing the holding step S10.

[0069] 5 and 6, the chuck table 18 is moved in the +X direction to a grinding position located directly below the X-axis direction moving mechanism 16. Fig. 5 is a partially sectional side view after the holding step S10 and before the groove forming step S20, and Fig. 6 is a top view after the holding step S10 and before the groove forming step S20.

[0070] After the holding step S10, without rotating the chuck table 18 and while rotating the grinding wheel 54 around the spindle 50, the chuck table 18 and the grinding wheel 54 are brought relatively close to each other along the Z-axis direction (the extension direction of the spindle 50).

[0071] In this embodiment, the grinding unit 46 is lowered (i.e., moved in the -Z direction) by the grinding feed mechanism 32, thereby bringing the grinding wheel 54 closer to the chuck table 18. Then, as shown in Figures 7 and 8, the grinding stone 58 is caused to cut into the dressing portion 15 to form an arc-shaped groove 15b in the dressing portion 15 (groove forming step S20).

[0072] In the groove forming step S20, for example, grinding water is supplied from the nozzle to the processing point at a predetermined rate of 2.0 L / min or more and 4.0 L / min or less, the grinding wheel 54 is rotated at a predetermined rate of 2000 rpm or more and 3000 rpm or less, and the grinding feed mechanism 32 grinds and feeds the grinding unit 46 in the -Z direction at a predetermined rate of 0.5 μm / s or more and 5.0 μm / s or less.

[0073] Fig. 7 is a partially cross-sectional side view showing the groove forming step S20, and Fig. 8 is a top view showing the groove forming step S20. In this embodiment, the lower surface 58c of the grinding wheel 58 is cut into the upper surface 15a of the dressing portion 15 to a depth of 6.0 mm to form the groove 15b.

[0074] After the groove forming step S20, the grinding feed of the grinding unit 46 is stopped while the grinding wheel 54 continues to rotate around the spindle 50. Then, the rotation of the chuck table 18 around the rotation axis 24 is started (see FIGS. 9 and 10).

[0075] In other words, with at least one of the multiple grinding wheels 58 on the rotating grinding wheel 54 inserted into the groove portion 15b, the chuck table 18 is rotated relatively slowly (e.g., at a rotational speed of 1.0 rpm) around the rotation axis 24 for a predetermined time (e.g., 3.0 s).

[0076] As a result, the inner surface 58a side is trued by the first side surface 15b1 of the groove portion 15b facing the inner surface 58a of the grinding wheel 58, and the outer surface 58b side is trued by the second side surface 15b2 of the groove portion 15b facing the outer surface 58b of the grinding wheel 58.

[0077] In this way, the first side surface 15b1 and the second side surface 15b2 are used to correct the shapes of the inner peripheral surface 58a and the outer peripheral surface 58b of all grinding wheels 58 (correction step S30). Fig. 9 is a partially cross-sectional side view showing the correction step S30, and Fig. 10 is a top view showing the correction step S30.

[0078] In the correction step S30, as shown in FIG. 10, the grinding wheel 58 is pressed against the first side surface 15b1 and the second side surface 15b2 (see the white arrows), thereby performing trueing so that the deviation between the rotation center 50a of the spindle 50 and the center 54a1 of the annular grinding surface 54a is reduced.

[0079] This reduces the deviation between the rotation center 50a of the grinding wheel 54 and the center 54a1 of the annular grinding surface 54a, thereby suppressing vibration of the grinding stone 58 when the workpiece 21 is ground.

[0080] For example, if the rotation speed of the chuck table 18 is set to 1.0 rpm and truing is performed for 3.0 seconds, the inner peripheral surfaces 58a and outer peripheral surfaces 58b of the grinding wheels 58 can be made concentric with the rotation center 50a.

[0081] In particular, by slowly rotating the chuck table 18 at 1.0 rpm over 3.0 seconds, the dressing portion 15 can be gradually brought into contact with the inner peripheral surface 58a and the outer peripheral surface 58b of the grinding wheel 58.

[0082] This makes it possible to suppress a sudden increase in load on the grinding wheel 58 compared to when the chuck table 18 is rotated instantaneously (for example, in a short time of less than 1.0 s) by a predetermined angle of 18° (= 1.0 rpm (i.e., 6.0° / s) × 3.0 s).

[0083] In this way, by truing the inner peripheral surface 58a side and the outer peripheral surface 58b side of the grinding wheel 58, the inner peripheral surface 58a side and the outer peripheral surface 58b side are ground down by, for example, 100 μm to 200 μm, and the misalignment (for example, a misalignment of 300 μm) between the center 54a1 of the grinding surface 54a and the rotation center 50a of the grinding wheel 54 is eliminated.

[0084] After the correction step S30, the chuck table 18 and the grinding wheel 54 are moved relatively apart along the extension direction of the spindle 50, thereby separating the plurality of grinding stones 58 from the dressing portion 15 (separation step S40). Figure 11 is a partial cross-sectional side view showing the separation step S40.

[0085] In the separation step S40 of this embodiment, the rotation of the chuck table 18 is stopped, and the grinding unit 46 is raised by the grinding feed mechanism 32 at a predetermined speed of 100 μm / s or more and 1000 μm / s or less, thereby separating the grinding wheel 54 from the chuck table 18.

[0086] However, the grinding unit 46 may be raised after the inner circumferential surface 58a and the outer circumferential surface 58b of the grinding wheel 58 are separated from the first side surface 15b1 and the second side surface 15b2 of the dressing part 15 by rotating the chuck table 18 in the direction opposite to the direction of rotation in the correction step S30. This makes it possible to prevent contact between the dressing part 15 and the grinding wheel 58 in the separation step S40.

[0087] Alternatively, the grinding unit 46 may be raised while slowly rotating the chuck table 18 in the direction opposite to the direction of rotation in the correction step S30 so that the inner surface 58a does not contact the first side surface 15b1 and the outer surface 58b does not contact the second side surface 15b2.

[0088] This prevents contact between the dressing portion 15 and the grinding wheel 58 in the separation step S40, and allows the separation step S40 to be started immediately after the correction step S30, thereby shortening the total time required to carry out the method for correcting the grinding wheel 58, including the separation step S40.

[0089] As described above, in this embodiment, by modifying the shapes of the inner peripheral surface 58a and the outer peripheral surface 58b of the multiple grinding wheels 58, the deviation between the rotation center 50a of the grinding wheel 54 and the center 54a1 of the annular grinding surface 54a can be reduced, thereby suppressing the vibration of the grinding wheels 58 that form the grinding area when grinding the workpiece 21.

[0090] (Modification) Next, a modification of the first embodiment will be described with reference to Figures 12(A) and 12(B). The shape and material of the dressing board 23 according to the modification are substantially the same as those of the dressing board 11.

[0091] However, an arc-shaped groove portion 25b having a width 25c (see Figure 12(A)) larger than the blade width 58d (see Figure 12(B)) of the grinding wheel 58 is pre-formed in the dressing portion 25 of the dressing board 23 from the upper surface 25a to a predetermined depth (e.g., 0.6 mm).

[0092] 12(A) is a top view showing a modified dressing board 23. When using the dressing board 23 to modify the shape of the inner surface 58a and outer surface 58b of the grinding wheel 58, first, in the holding step S10, the holding surface 18a of the chuck table 18 holds the lower surface 13b of the support base 13 by suction.

[0093] Next, the groove forming step S20 is omitted and the process proceeds to the correction step S30. In the correction step S30, the grinding stone 58 of the rotating grinding wheel 54 is inserted into the groove 15b, and the chuck table 18 starts to rotate (see FIG. 12(B)). FIG. 12(B) is a top view showing the correction step S30 according to a modified example.

[0094] In the correction step S30, the shapes of the inner surface 58a and outer surface 58b of all grinding wheels 58 are corrected using the first side 25b1 and second side 25b2 of the groove portion 25b, and then in the separation step S40, the grinding wheel 54 is separated from the dressing portion 25.

[0095] Even with this deformation, the deviation between the rotation center 50a of the grinding wheel 54 and the center 54a1 of the grinding surface 54a can be reduced, so that vibration of the grinding stone 58 that forms the grinding area when the workpiece 21 is ground can be suppressed.

[0096] Next, a second embodiment will be described. In the second embodiment, a grinding machine 60 is used to perform grinding known as TAIKO (registered trademark) on a workpiece 31 (see FIG. 14(A)).

[0097] 13 is a partial cross-sectional side view of a grinding device 60 according to the second embodiment. Components that are substantially the same as those in the grinding device 2 are denoted by the same reference numerals as those in FIG. 2, and descriptions of the components of the grinding device 60 may be omitted.

[0098] The grinding device 60 has a disk-shaped chuck table 62. The chuck table 62 has a disk-shaped frame body 64 made of ceramics. A disk-shaped recess having a predetermined depth is formed in the center of the frame body 64.

[0099] A tube portion, a groove portion, and the like (not shown) connected to a suction source (not shown) such as a vacuum pump are formed on the frame 64. A disk-shaped porous plate 66 made of porous ceramics and having approximately the same diameter as the inner diameter of the recess is fixed to the recess.

[0100] When negative pressure is transmitted from the suction source to the tube, groove, etc., negative pressure is generated on the upper surface of the porous plate 66. The upper surface of the frame 64 and the upper surface of the porous plate 66 form a holding surface 62a that is approximately flush with each other. As shown in Figure 13, the holding surface 62a has a biconcave shape in a cross section passing through the center in the radial direction when viewed from above.

[0101] The holding surface 62a holds by suction the above-mentioned dressing board 11, workpiece 31 (see FIG. 14(A)), etc. A grinding unit 68 is disposed above the holding surface 62a. The grinding unit 68 has a spindle housing 48 fixed to the moving block 36.

[0102] A portion of the spindle 50 is rotatably housed in the spindle housing 48. The spindle 50 is disposed along the Z-axis direction, and an annular grinding wheel 70 is attached to the lower end of the spindle 50 via a disk-shaped mount 52.

[0103] The grinding wheel 70 of this embodiment has a diameter approximately half that of the holding surface 62a. The grinding wheel 70 has an annular wheel base 72 made of metal such as an aluminum alloy. A plurality of grinding stones 74 are arranged in an annular shape on the underside of the wheel base 72 at approximately equal intervals along the circumferential direction of the wheel base 72.

[0104] As shown in Fig. 14(A), the workpiece 31 to be ground by the grinding unit 68 is a disk-shaped single crystal silicon wafer having a predetermined diameter (for example, a diameter of about 200 mm). Fig. 14(A) is a perspective view of the workpiece 31.

[0105] There are no limitations on the type, material, size, shape, structure, etc. of the workpiece 31. The workpiece 31 may have a single crystal substrate made of a compound semiconductor (GaN, SiC, etc.) or the like.

[0106] The workpiece 31 has a front surface 31a and a back surface 31b. The length from the front surface 31a to the back surface 31b (i.e., the thickness of the workpiece 31) is a predetermined value (for example, 725 μm) of 200 μm to 800 μm.

[0107] A plurality of planned division lines 33 are set in a grid pattern on the surface 31a. Devices 35 such as ICs are formed on the surface 31a side of each rectangular area partitioned by the plurality of planned division lines 33. However, there are no restrictions on the type, number, shape, structure, size, arrangement, etc. of the devices 35.

[0108] Around the device region 37a where the plurality of devices 35 are formed, there exists a substantially flat annular peripheral excess region 37b where no devices 35 are formed, so as to surround the device region 37a in a plan view.

[0109] Before grinding the workpiece 31, a circular resin protective tape 39 is attached to the front surface 31a to reduce damage to the device 35 during grinding. When grinding the workpiece 31, a predetermined region 37c (see FIG. 14(B)) on the back surface 31b corresponding to the device region 37a is ground to a predetermined depth to form a disk-shaped recess 31c1.

[0110] As a result, a disk-shaped thinned portion 31c2 located closer to the front surface 31a than the recessed portion 31c1 and a ring-shaped reinforcing portion 31d surrounding the sides of the recessed portion 31c1 and the thinned portion 31c2 are formed in the workpiece 31. Fig. 14(B) is a cross-sectional view of the workpiece 31 after grinding in the second embodiment.

[0111] Incidentally, when the grinding wheel 74 constituting the grinding area oscillates in a predetermined direction within the X-Y plane during grinding of the workpiece 31, the outer peripheral portion 31e of the bottom of the recess 31c1 becomes an arc having a predetermined curvature in cross section (see Figure 14(C)) rather than being approximately right-angled (see Figure 14(B)).

[0112] 14(C) is a cross-sectional view of the workpiece 31 after grinding in the comparative example, in which the outer peripheral portion 31f at the bottom of the recess 31c1 is an arc-shaped portion having a predetermined curvature. When the outer peripheral portion 31f shown in FIG. 14(C) is formed, the effective area of ​​the device region 37a is reduced, so it is preferable to modify the shape of the grinding wheel 74 before grinding the workpiece 31.

[0113] Fig. 15 is a flow diagram of the grinding method for the workpiece 31 in the second embodiment. The steps from the holding step S10 to the separating step S40 shown in Fig. 15 have already been described with reference to Figs. 1 to 11, and therefore description thereof will be omitted.

[0114] In this embodiment, the steps from the holding step S10 to the separation step S40 are collectively referred to as a shape modification step S50 for the grinding wheels 74. In the shape modification step S50, as described above, the dressing board 11 is used to modify the shapes of the inner peripheral surface 74a and the outer peripheral surface 74b (see FIG. 13) of all the grinding wheels 58.

[0115] This reduces the deviation between the center of rotation 50a of the grinding wheel 70 and the center (not shown) of the annular grinding surface 70a defined by the lower surfaces 74c of the multiple grinding stones 74, thereby suppressing the vibration of the grinding stones 74 that form the grinding area when grinding the workpiece 31.

[0116] After the shape correcting step S50, the workpiece 31 is placed on the holding surface 62a instead of the dressing board 11, and the front surface 31a side is suction-held by the holding surface 62a via the protective tape 39 (workpiece holding step S60).

[0117] After the workpiece holding step S60, the inclination of the table base 28 is adjusted appropriately, and the chuck table 62 is rotated at a predetermined rotation speed around the rotation axis 24. Furthermore, with the grinding wheel 70 rotating around the spindle 50, the chuck table 62 and the grinding unit 68 are brought relatively close to each other along the extension direction of the spindle 50.

[0118] In this embodiment, the grinding unit 68 is lowered by the grinding feed mechanism 32, thereby bringing the grinding wheel 70 closer to the chuck table 62. In this manner, the predetermined region 37c is ground, and a recess 31c1 having a substantially right angle in cross section is formed in the outer periphery 31e of the bottom, as shown in Fig. 14(B) (recess formation step S70).

[0119] The grinding feed rate of the grinding unit 68 is adjusted as appropriate so as to leave the thinned portion 31c2 with a predetermined thickness. In this embodiment, for convenience, the workpiece holding step S60 and the recess forming step S70 are collectively referred to as a grinding step S80.

[0120] In this embodiment, the outer periphery 31e of the bottom of the recess 31c1 is approximately right-angled in cross section, so the effective range of the device region 37a can be made larger than when the outer periphery 31f of the bottom of the recess 31c1 is arc-shaped with a predetermined curvature in cross section.

[0121] Furthermore, the shape modifying step S50 reduces the roughness and TTV (Total Thickness Variation) on the bottom surface of the recess 31c1 (i.e., the surface on the back surface 11b side of the thinned portion 31c2), and suppresses cracking of the workpiece 31. Furthermore, wear of the grinding wheel 74 can be reduced compared to when the shape modifying step S50 is not performed.

[0122] In addition, the structures, methods, etc. according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention. In the above-described embodiments, the grinding units 46, 68 are lowered along the Z-axis direction, but the chuck tables 18, 62 may be raised along the Z-axis direction.

[0123] In addition, in the correction step S30, instead of the dressing board 11, the shape of the inner surface 58a side and the outer surface 58b side of the grinding wheel 58 may be corrected using the ring-shaped reinforcing portion 31d of the workpiece 31 having the thinned portion 31c2 and the ring-shaped reinforcing portion 31d. [Explanation of symbols]

[0124] 2: Grinding device, 4: Base 6: Guide rail, 8: Moving plate, 10: Nut part, 12: Screw shaft, 14: Motor 11: Dressing board, 13: Support base, 13a: Upper surface, 13b: Lower surface 15: Dressing section 15a: Top surface, 15b: Groove, 15b1: First side, 15b2: Second side 16: X-axis direction moving mechanism, 18: chuck table, 18a: holding surface, 20: frame body 21: Workpiece 22: porous plate, 24: rotation axis (first rotation axis), 24a: rotation center 23: Dressing board, 25: Dressing section 25a: Top surface, 25b: Groove, 25b1: First side, 25b2: Second side, 25c: Width 26: Bearing, 28: Table base, 30: Wall 30a: Fixed support mechanism, 30b: First movable support mechanism, 30c: Second movable support mechanism 31: Workpiece, 31a: Front surface, 31b: Back surface, 31c1: Concave portion, 31c2: Thinned portion 31d: ring-shaped reinforcement portion, 31e: outer periphery, 31f: outer periphery, 33: planned division line 32: Grinding feed mechanism, 34: Guide rail, 36: Moving block 35: device, 37a: device area, 37b: peripheral excess area, 37c: predetermined area 38: Nut portion, 40: Screw shaft, 42: Motor, 44: Fixture 39: Protective tape 46: Grinding unit, 48: Spindle housing 50: spindle (second rotation axis), 50a: rotation center 52: mount, 54: grinding wheel, 54a: grinding surface, 54a1: center 56: Wheel base, 56a: Bottom surface 58: Grinding wheel, 58a: Inner circumferential surface, 58b: Outer circumferential surface, 58c: Bottom surface, 58d: Blade width 60: grinding device, 62: chuck table, 62a: holding surface 64: Frame, 66: Porous plate 68: Grinding unit, 70: Grinding wheel, 70a: Grinding surface 72: Wheel base, 74: Grinding wheel, 74a: Inner surface, 74b: Outer surface, 74c: Bottom surface S10: Holding step, S20: Groove forming step, S30: Repair step S40: Separation step, S50: Shape correction step, S60: Workpiece holding step S70: Recess formation step, S80: Grinding step

Claims

1. A correction method for correcting the shapes of inner and outer peripheral surfaces of a grinding wheel having a plurality of grinding stones arranged in a ring, the method comprising: a holding step of suction-holding a lower surface of a support base of a dressing board having a dressing portion fixed to an upper surface of the support base on a holding surface of a chuck table; a correction step of rotating the grinding wheel around a second rotation axis that rotates the grinding wheel with at least one grinding wheel among the plurality of grinding wheels inserted into an arc-shaped groove formed in the dressing portion after the holding step, and further rotating the chuck table around a first rotation axis, thereby correcting the shapes of the inner peripheral surface side and the outer peripheral surface side of the plurality of grinding wheels by using a first side surface of the groove facing the inner peripheral surfaces of the plurality of grinding wheels and a second side surface of the groove facing the outer peripheral surfaces of the plurality of grinding wheels so as to reduce the deviation between the second rotation axis and the center of an annular grinding surface defined by the lower surfaces of the plurality of grinding wheels; a separation step of separating the plurality of grinding stones from the dressing portion by moving the chuck table and the grinding wheel relatively apart along the extension direction of the second rotation axis after the correction step.

2. 2. The correction method according to claim 1, further comprising a groove forming step of forming the groove in the dressing portion by bringing the chuck table and the grinding wheel relatively close to each other along an extension direction of the second rotation axis while the chuck table is not rotating and the grinding wheel is rotating around the second rotation axis after the holding step and before the correction step.

3. The correction method described in claim 1, characterized in that the dressing board held by suction on the holding surface in the holding step has an arc-shaped groove portion formed in the dressing portion having a width greater than the blade width of the grinding wheel.

4. A method for grinding a workpiece, the workpiece having, on its front surface side, a device region in which a plurality of devices are formed and a peripheral excess region surrounding the device region, the method comprising: grinding a predetermined region on a back surface side of the workpiece corresponding to the device region, the method comprising: a shape modifying step of modifying the shapes of the inner peripheral surface side and the outer peripheral surface side of the grinding wheels of a grinding wheel having a plurality of grinding wheels arranged in a ring; a grinding step in which, after the shape modifying step, the chuck table is rotated about a first rotation axis, and the grinding wheel is rotated about a second rotation axis, and the chuck table and the grinding wheel are moved relatively close to each other along an extension direction of the second rotation axis, thereby grinding the predetermined region of the workpiece with the grinding wheel, The shape modification step includes: a holding step of suction-holding a lower surface of a support base of a dressing board having a dressing portion fixed to an upper surface of the support base on a holding surface of the chuck table; a groove forming step of forming a groove in the dressing portion by moving the chuck table and the grinding wheel relatively close to each other along the second rotation axis while rotating the grinding wheel around the second rotation axis without rotating the chuck table after the holding step; a modification step of, after the groove forming step, rotating the grinding wheel around the second rotation axis with at least one grinding wheel among the plurality of grinding wheels inserted into the arc-shaped groove formed in the dressing part, and further rotating the chuck table around the first rotation axis, thereby modifying the shapes of the inner peripheral surface side and the outer peripheral surface side of the plurality of grinding wheels by using a first side surface of the groove facing the inner peripheral surfaces of the plurality of grinding wheels and a second side surface of the groove facing the outer peripheral surfaces of the plurality of grinding wheels so as to reduce a deviation between the second rotation axis and a center of an annular grinding surface defined by the lower surfaces of the plurality of grinding wheels; a separating step of separating the plurality of grinding stones from the dressing portion by moving the chuck table and the grinding wheel relatively apart along an extending direction of the second rotation axis after the adjusting step, The grinding step includes: a workpiece holding step of holding the front surface side of the workpiece with the holding surface; a recess forming step of, after the workpiece holding step, grinding the predetermined area on the back side of the workpiece corresponding to the device area with the grinding wheel to form a disk-shaped thinned portion and a ring-shaped reinforcing portion surrounding the thinned portion.

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