Grinding method for a curved plate-shaped workpiece

Abstract

To reduce grindstone replacing work and eliminate necessity of stockpiling a plurality of types of grindstones when bent plate-like workpiece is ground by reducing force for separating the bent plate like workpiece from a holding surface.SOLUTION: A plate-like workpiece grinding method comprises steps of: holding bent plate-like workpiece having force in a direction in which an outer peripheral part is separated from a holding surface 302 on the holding surface 302 of a table 3, lowering a grindstone 1642 positioned above the plate-like workpiece in a direction perpendicular to the holding surface 302, and biting the grindstone 1642 into the plate-like workpiece to form a circular-arc groove without rotating the holding surface 302; relatively moving at least one of the grindstone 1642 and the table 3 so as to position the grindstone 1642 to a location different from the location of the grindstone 1642 positioned with respect to the plate-like workpiece in the circular-arc groove forming step; repeating the circular-arc groove forming step and the grindstone moving step to form a plurality of grooves on the upper surface of the plate-like workpiece, thereby correcting the bending; and grinding, after the grooves have been formed, the upper surface of the plate-like workpiece to remove the grooves, and grinding the workpiece to a prescribed thickness.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for grinding a plate-shaped workpiece, which grinds a plate-shaped workpiece that is curved with a grinding wheel.

Background Art

[0002] For example, as disclosed in Patent Document 1 below, when grinding a plate-shaped workpiece having a force that causes the outer peripheral portion sucked and held on the holding surface of the chuck table to warp upward with a grinding wheel, the frictional force between the grinding wheel and the plate-shaped workpiece, and the warping force of the plate-shaped workpiece may cause the outer peripheral portion of the plate-shaped workpiece to float from the holding surface and the plate-shaped workpiece to separate from the holding surface.

[0003] And, in order to prevent the curved plate-shaped workpiece from separating from the holding surface, a cutting groove is formed on the upper surface, which is the surface to be ground of the plate-shaped workpiece, before grinding, to correct the curvature of the plate-shaped workpiece and weaken the warping force.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventionally, a cutting wheel has been used to form a cutting groove in this plate-shaped workpiece. Therefore, the processing apparatus includes a cutting mechanism equipped with a cutting wheel for forming a groove in the plate-shaped workpiece and a grinding mechanism equipped with a grinding wheel for grinding and thinning the plate-shaped workpiece. An operator may frequently replace the cutting wheel and the grinding wheel, and it is necessary to replace two types of wheels and stock two types of wheels.

[0006] Therefore, when grinding a plate-shaped workpiece with a curvature that causes it to warp upward, reducing the force that attempts to separate it from the holding surface of the chuck table of the grinding device, there is a problem of reducing the frequency of grinding wheel replacement work and eliminating the need to have an inventory of multiple types of grinding wheels.

Means for Solving the Problem

[0007] The present invention for solving the above problems is A grinding apparatus comprising a chuck table having a holding surface, a horizontal movement unit for horizontally moving the chuck table in a direction parallel to the holding surface, a grinding unit including a plurality of grinding wheels arranged in a ring shape, and a lifting unit for raising and lowering the grinding unit in a direction perpendicular to the holding surface is used. The A method for grinding a plate-shaped workpiece, in which the upper surface of the plate-shaped workpiece having a force in a direction away from the holding surface of the chuck table is ground with an annular grinding wheel, lower surface of the plate-shaped workpiece is pressed against the holding surface, and in a state where the curvature is temporarily eliminated, the holding the plate-shaped workpiece on the holding surface, and positioning the grinding wheel above the plate-shaped workpiece held on the holding surface lifting unit lowering it in a direction perpendicular to the holding surface, and forming an arc-shaped groove by cutting the grinding wheel into the upper surface of the plate-shaped workpiece without rotating the holding surface, an arc groove forming step; and positioning the grinding wheel at a position different from the position of the grinding wheel positioned with respect to the plate-shaped workpiece in the arc groove forming step, horizontal movement unit moving the chuck table in a direction parallel to the holding surface table a moving step; the arc groove forming step; and the table moving step are repeated to form a plurality of the grooves on the upper surface of the plate-shaped workpiece to correct the curvature of the plate-shaped workpiece, a plurality of groove forming steps; and after forming a plurality of the grooves, grinding wheel grinding the upper surface of the plate-shaped workpiece to remove the grooves and grinding the plate-shaped workpiece to a predetermined thickness, a grinding step, which is a method for grinding a plate-shaped workpiece.

[0008] In the method for grinding a plate-shaped workpiece according to the present invention, in the grinding step, the chuck table is rotated about the center of the holding surface, and the center of rotation of the plate-shaped workpiece held on the rotating holding surface is passed through the grinding wheel by the lifting unit lowering it in a direction perpendicular to the holding surface the lower surface of the grinding wheel is brought into contact with the plate-shaped workpiece to grind the plate-shaped workpiece, which is preferable.

[0009] In the method for grinding a plate-shaped workpiece according to the present invention, in the grinding step, the lower surface of the grinding wheel is positioned below the upper surface of the plate-shaped workpiece and outside the outer periphery of the plate-shaped workpiece held on the holding surface. the chuck table is horizontally moved by the horizontal movement unit, It is preferable to grind the plate-shaped workpiece.

[0010] In the method for grinding a plate-shaped workpiece according to the present invention, in the arc groove forming step, the chuck table is tilted so that the front side in the traveling direction is lower than the rear side, It is preferable to cut into the upper surface of the plate-shaped workpiece held by the holding surface from the outer peripheral corner of the lower surface of the grinding wheel.

[0011] In the method for grinding a plate-shaped workpiece according to the present invention, in the arc groove forming step, the chuck table is tilted so that the front side in the traveling direction is higher than the rear side, It is preferable to cut into the upper surface of the plate-shaped workpiece held by the holding surface from the inner peripheral corner of the lower surface of the grinding wheel.

Advantages of the Invention

[0012] The grinding method of a plate-shaped workpiece according to the present invention for grinding the upper surface of a curved plate-shaped workpiece having a force in a direction in which the outer peripheral portion held by the holding surface of the chuck table separates from the holding surface with an annular grinding wheel. The chuck table holds the plate-shaped workpiece on the holding surface, lowers a grinding wheel positioned above the plate-shaped workpiece held on the holding surface in a direction perpendicular to the holding surface, and cuts the grinding wheel into the upper surface of the plate-shaped workpiece without rotating the holding surface to form an arc groove. An arc groove forming step; a grinding wheel moving step of moving at least one of the grinding wheel and the chuck table relatively in a direction parallel to the holding surface so as to position the grinding wheel at a position different from the position of the grinding wheel positioned with respect to the plate-shaped workpiece in the arc groove forming step; and an arc groove forming step and a grinding wheel moving step are repeated to form a plurality of grooves on the upper surface of the plate-shaped workpiece to correct the curvature of the plate-shaped workpiece. By providing a plurality of groove forming steps, before grinding and thinning the plate-shaped workpiece, the force that the plate-shaped workpiece tends to separate from the holding surface is reduced. After forming a plurality of grooves, the upper surface of the plate-shaped workpiece is ground to remove the grooves, and the occurrence of vacuum leakage is prevented by preventing the plate-shaped workpiece from separating from the holding surface, and the plate-shaped workpiece can be ground to a predetermined thickness. Further, since groove processing and grinding are performed only with the grinding wheel, the types of grinding wheels can be reduced, and it is not necessary to have an inventory of a plurality of types of grinding wheels in the grinding apparatus.

[0013] In the grinding step, the chuck table is rotated about the center of the holding surface, and a grinding wheel passing through the rotation center of the plate-shaped workpiece held on the rotating holding surface is lowered in a direction perpendicular to the holding surface to grind the plate-shaped workpiece, that is, by performing infeed grinding, it is possible to remove the grooves and make the upper surface of the plate-shaped workpiece a flat surface, and to thin the plate-shaped workpiece to a predetermined thickness.

[0014] In the grinding process, the lower surface of the grinding wheel is positioned below the upper surface of the plate-shaped workpiece and outside the outer circumference of the plate-shaped workpiece held on the holding surface. The plate-shaped workpiece and the grinding wheel are relatively moved closer to each other in a direction parallel to the holding surface to grind the plate-shaped workpiece, that is, to perform creep feed grinding. By doing so, it is possible to remove the grooves and make the upper surface of the plate-shaped workpiece flat, and appropriately thin the plate-shaped workpiece to a predetermined thickness.

[0015] In the arc groove forming process, by relatively changing the inclination of the holding surface of the chuck table with respect to the lower surface of the grinding wheel and cutting into the upper surface of the plate-shaped workpiece held by the holding surface from the outer peripheral angle of the lower surface of the grinding wheel, it becomes possible to appropriately form a groove for correcting the curvature of the plate-shaped workpiece.

[0016] In the arc groove forming process, by relatively changing the inclination of the holding surface of the chuck table with respect to the lower surface of the grinding wheel and cutting into the upper surface of the plate-shaped workpiece held by the holding surface from the inner peripheral angle of the lower surface of the grinding wheel, it becomes possible to appropriately form a groove for correcting the curvature of the plate-shaped workpiece. Also, in the grinding process performed after implementing a plurality of groove forming processes that repeat the arc groove forming process and the grinding wheel moving process, for example, when performing creep feed grinding, it becomes possible to prevent the outer surface of the grinding wheel, which is the part mainly grinding the plate-shaped workpiece in creep feed grinding, from being consumed.

Brief Explanation of Drawings

[0017]

Figure 1

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Embodiments for Carrying Out the Invention

[0018] The grinding device 1 shown in FIG. 1 is a device that grinds a plate-shaped workpiece 90 sucked and held on a chuck table 3 by a grinding unit 16. The front (-Y direction side) on the device base 10 whose longitudinal direction is the Y-axis direction of the grinding device 1 is a detaching / attaching region where the plate-shaped workpiece 90 is detached / attached to / from the chuck table 3, and the rear (+Y direction side) on the device base 10 is a grinding region where the plate-shaped workpiece 90 sucked and held on the chuck table 3 by the grinding unit 16 is ground. Note that the grinding device used to implement the grinding method according to the present invention is not limited to a one-axis type of grinding unit 16 such as the grinding device 1, and includes a rough grinding unit and a finish grinding unit, and is a two-axis type that can position the plate-shaped workpiece 90 below the rough grinding unit or the finish grinding unit by a rotating turntable. It may be of the type.

[0019] The plate-shaped workpiece 90 shown in FIG. 1 has, for example, silicon chips arranged at equal intervals on the upper surface of a rectangular substrate made of a PCB or the like, and the upper surface of the substrate including the silicon chips is molded with an epoxy resin or the like. Then, due to the shrinkage force of the mold resin or the like, the plate-shaped workpiece 90 having a rectangular shape in plan view is curved as a whole. That is, as shown in FIG. 2, the curvature of the plate-shaped workpiece 90 is a warp that gradually increases from the central region of the lower surface 902 where the plate-shaped workpiece 90 is sucked and held toward the outer peripheral region. Then, the upper surface 904 of the plate-shaped workpiece 90 becomes the surface to be ground, and a protective tape 9000 for protecting the lower surface 902 is attached to the lower surface 902 of the plate-shaped workpiece 90. Note that the plate-shaped workpiece 90 having a polygonal (rectangular) shape in the present embodiment is not limited to this, and may be a silicon wafer or the like having a circular shape in plan view.

[0020] As shown in FIGS. 1 and 3, the chuck table 3 includes, for example, a porous portion 30 having a rectangular holding surface 302 and a frame body 31 that supports the porous portion 30. The holding surface 302 communicates with a suction source (not shown) such as a vacuum generator or an ejector mechanism.

[0021] As shown in FIG. 1, the chuck table 3 is surrounded from the periphery by a cover 39 and is rotatable about the Z-axis by a table rotation mechanism 33 including a rotation shaft, a motor, and an encoder that detects the rotation angle of the motor, which are connected to the lower surface side thereof.

[0022] As shown in FIG. 1, inside the apparatus base 10, a horizontal movement unit 13 for horizontally moving the chuck table 3 is disposed at a grinding position where the grinding wheel 164 grinds the plate-shaped workpiece 90 and at a loading / unloading position where the plate-shaped workpiece 90 can be loaded onto the holding surface 302 of the chuck table 3 or unloaded from the holding surface 302. The horizontal movement unit 13 includes a ball screw 130 having an axis in the Y-axis direction, a pair of guide rails 131 disposed in parallel with the ball screw 130, a motor 132 connected to one end of the ball screw 130 to rotate the ball screw 130, and a movable plate 133 whose internal nut is screwed onto the ball screw 130 and whose bottom is in sliding contact with the guide rail 131. When the motor 132 rotates the ball screw 130, the movable plate 133 is guided by the guide rail 131 and linearly moves in the Y-axis direction, and as shown in FIGS. 1 and 3, the chuck table 3 disposed via the inclination adjustment unit 37, the table rotation mechanism 33, and the chuck base 35 (not shown in FIG. 3) on the movable plate 133 can be moved in the Y-axis direction. Note that the horizontal movement unit 13 may be a turntable having a plurality of chuck tables 3 disposed on the upper surface and rotatable.

[0023] As shown in FIG. 1, the chuck table 3 is attached to the upper surface of the chuck base 35, and the chuck base 35 is supported by an inclination adjustment unit 37 that adjusts the inclination of the holding surface 302 of the chuck table 3. As shown in FIG. 3, on the movable plate 133 of the horizontal movement unit 13, two or more inclination adjustment units 37 are provided, for example, circumferentially at equal intervals around the center of the holding surface 302 of the chuck table 3 on the lower surface side of the chuck base 35. That is, for example, two inclination adjustment units 37 and a support column (not shown) extending in the Z-axis direction for fixing the chuck base 35 are arranged at intervals of 120 degrees in the circumferential direction. The two inclination adjustment units 37 are, for example, electric cylinders or air cylinders in which the piston rod 371 can move up and down in the Z-axis direction. By moving the piston rods 371 of the two inclination adjustment units 37 shown in FIG. 3 up and down, the inclination of the grinding wheel 1642 of the grinding unit 16 with respect to the lower surface of the holding surface 302 can be adjusted. Note that an inclination adjustment unit may be provided on the grinding unit 16 side.

[0024] As shown in FIG. 1, a column 11 is erected in the grinding area, and on the front surface on the -Y direction side of the column 11, a lifting unit 17 for grinding feed in the vertical direction, that is, in the Z-axis direction perpendicular to the holding surface 302 of the chuck table 3, is provided for the grinding unit 16. The lifting unit 17 includes a ball screw 170 extending in the Z-axis direction, a pair of guide rails 171 arranged in parallel with the ball screw 170, a lifting motor 172 connected to the upper end of the ball screw 170 and rotating the ball screw 170, and a lifting plate 173 whose internal nut is screwed onto the ball screw 170 and whose side portion is in sliding contact with the guide rail 171. When the lifting motor 172 rotates the ball screw 170, the lifting plate 173 is guided by the guide rail 171 and reciprocates in the Z-axis direction accordingly, and the grinding unit 16 fixed to the lifting plate 173 is fed for grinding in the Z-axis direction.

[0025] The grinding unit 16 for grinding the plate-shaped workpiece 90 held on the chuck table 3 includes a rotating shaft 160 whose axial direction is the Z-axis direction, a housing 161 that rotatably supports the rotating shaft 160, a motor 162 that rotationally drives the rotating shaft 160, an annular mount 163 connected to the lower end of the rotating shaft 160, a grinding wheel 164 detachably attached to the lower surface of the mount 163, and a holder 165 that supports the housing 161 and is fixed to the lifting plate 173 of the lifting unit 17.

[0026] The grinding wheel 164 includes a wheel base 1641 and a plurality of substantially rectangular parallelepiped-shaped grinding wheels 1642 annularly arranged on the bottom surface of the wheel base 1641. The grinding wheels 1642 are formed by fixing diamond abrasive grains or the like with, for example, resin bond or vitrified bond. The blade width of the annular grinding wheel 1642 is set to, for example, 1 mm to 3 mm.

[0027] For example, the diameter of the grinding wheel 164 is larger than that of the plate-shaped workpiece 90 such that the arc-shaped grinding wheel 1642 can cross from one side to the opposite side of the plate-shaped workpiece 90 with sufficient margin. Note that when the arc groove forming step of Embodiment 4 described later in the grinding direction according to the present invention is not performed, the diameter of the grinding wheel 164 may be smaller than the size of the plate-shaped workpiece 90.

[0028] Inside the rotating shaft 160, a flow path (not shown) that communicates with a grinding water supply source and serves as a passage for grinding water is provided to penetrate in the axial direction of the rotating shaft 160. The flow path (not shown) further passes through the mount 163 and opens at the bottom surface of the wheel base 1641 so as to jet grinding water toward the grinding wheel 1642.

[0029] In the present embodiment, the grinding unit 16 and the lifting unit 17 are reciprocally movable in the X-axis direction by an X-axis moving unit 18 disposed, for example, on the front surface of the column 11. The X-axis moving unit 18 includes a ball screw 180 whose axial direction is the X-axis direction, a pair of guide rails 181 arranged in parallel with the ball screw 180, a motor 182 connected to one end of the ball screw 180 to rotate the ball screw 180, and a movable plate 183 whose internal nut is screwed onto the ball screw 180 and whose side is in sliding contact with the guide rail 181. When the motor 182 rotates the ball screw 180, the movable plate 183 is guided by the guide rail 181 and reciprocates in the X-axis direction, and the grinding unit 16 and the lifting unit 17 arranged on the movable plate 183 reciprocate in the X-axis direction.

[0030] As shown in FIG. 1, at a position adjacent to the grinding unit 16 in the state of descending to the grinding position, for example, a thickness measuring unit 104 for measuring the thickness of the plate-shaped workpiece 90 in a contact manner is arranged. The thickness measuring unit 104 measures the height position of the holding surface 302 serving as a reference surface, that is, in this embodiment, the height position of the upper surface of the frame body 31 at the same height as the holding surface 302, by means of a first linear gauge, and measures the height position of the upper surface 904 of the plate-shaped workpiece 90 to be ground by means of a second linear gauge, and calculates the difference between the measured values of both linear gauges, so that the thickness of the plate-shaped workpiece 90 can be sequentially measured during grinding. Note that the thickness measuring unit 104 may be of a non-contact type.

[0031] For example, at a position beside the moving path of the chuck table 3 in the attachment / detachment area on the apparatus base 10 shown in FIG. 1, a pressing mechanism 4 for pressing the plate-shaped workpiece 90 placed on the holding surface 302 of the chuck table 3 from above downward for suction holding is arranged.

[0032] The pressing mechanism 4 includes a lifting mechanism 40 such as an electric cylinder or an air cylinder arranged on the apparatus base 10, an arm portion 41 whose rear end is attached to the upper end side of a lifting rod (not shown) that moves up and down in the Z-axis direction of the lifting mechanism 40 and extends horizontally above the moving path of the chuck table 3, and a pressing pad 44 attached to the lower surface of the tip of the arm portion 41. The arm portion 41 is, for example, capable of swinging and moving in a horizontal plane (in the X-axis Y-axis plane) about a rotation axis in the Z-axis direction.

[0033] It can be moved up and down in the Z-axis direction by the lifting mechanism 40, and the pressing pad 44 that can be directly opposed to the center of the holding surface 302 of the chuck table 3 in the Z-axis direction is formed, for example, in a rectangle having the same size as the plate-shaped workpiece 90 in a plan view or slightly larger than the plate-shaped workpiece 90. The flat lower surface 443 of the pressing pad 44 contacts the upper surface 904 of the plate-shaped workpiece 90.

[0034] Hereinafter, when the grinding method according to the present invention is implemented and the plate-shaped workpiece 90 held on the chuck table 3 is ground by the grinding device 1 shown in FIG. 1, each step and the operation of each component of the grinding device 1 will be described. First, the chuck table 3 shown in FIGS. 1 and 3 is moved in the -Y direction by the horizontal movement unit 13 and positioned, for example, directly below the pressing pad 44 of the pressing mechanism 4 within the attachment / detachment area. Also, the pressing pad 44 arranged at the tip of the arm portion 41 is rotated about the rotation axis 45 passing through the center of the lifting mechanism 40 so that the shape of the pressing pad 44 substantially matches the shape of the holding surface 302 of the chuck table 3.

[0035] Next, for example, by an operator, as shown in FIG. 3, the plate-shaped workpiece 90 is placed on the holding surface 302 in a state where the centers of the plate-shaped workpiece 90 and the holding surface 302 substantially coincide with each other, and the shape of the holding surface 302 and the shape of the plate-shaped workpiece 90 substantially coincide with each other. Here, the plate-shaped workpiece 90 is arranged on the holding surface 302 so as to gradually become higher from the central region of the lower surface 902 toward the outer peripheral side region.

[0036] When the suction force generated by the operation of a suction source (not shown) is transmitted to the holding surface 302, the chuck table 3 first sucks and holds the central region of the lower surface 902 of the plate-shaped workpiece 90 (in this embodiment, the central region of the lower surface of the protective tape 9000) on the holding surface 302.

[0037] Furthermore, the pressing pad 44 descends at a predetermined speed by the elevating mechanism 40 shown in FIG. 1. The pressing pad 44 presses the plate-shaped workpiece 90 so that the outer peripheral side region of the lower surface 902 of the plate-shaped workpiece 90 corrects the curvature on the holding surface 302. Then, the plate-shaped workpiece 90 is sucked and held on the chuck table 3 without vacuum leakage in a state where the warp of the outer peripheral portion, that is, the overall curvature is temporarily eliminated. Note that, without forming a groove described later on the upper surface 904 of the plate-shaped workpiece 90, next, when the grinding wheel 1642 is continuously brought into contact with the upper surface 904 of the plate-shaped workpiece 90 and the plate-shaped workpiece 90 rotated by the chuck table 3, for example, is ground, the curvature of the plate-shaped workpiece 90 may be restored during grinding due to the frictional force acting between the grinding wheel 1642 and the upper surface 904 of the plate-shaped workpiece 90, resulting in vacuum leakage or the like.

[0038] After the plate-shaped workpiece 90 is sucked and held on the chuck table 3 in a state where the curvature is temporarily eliminated, the pressing pad 44 ascends and separates from the plate-shaped workpiece 90. Next, the horizontal movement unit 13 moves the chuck table 3 holding the plate-shaped workpiece 90 to below the grinding unit 16 shown in FIGS. 1 and 3, and alignment is performed between the grinding wheel 164 and the plate-shaped workpiece 90.

[0039] (1-1) Embodiment 1 of the arc groove forming process Hereinafter, an arc groove forming process of Embodiment 1 will be described in which the grinding wheel 1642 positioned above the plate-shaped workpiece 90 sucked and held on the holding surface 302 of the chuck table 3 shown in FIG. 3 is lowered in a direction perpendicular to the holding surface 302 (Z-axis direction), and the grinding wheel 1642 is cut into the upper surface 904 of the plate-shaped workpiece 90 without rotating the holding surface 302 to form an arc groove.

[0040] For example, in the present Embodiment 1, the inclination of the chuck base 35 and the chuck table 3 is adjusted by the inclination adjustment unit 37 shown in FIG. 3, so that the upper surface 904 of the plate-shaped workpiece 90 sucked and held on the holding surface 302 becomes substantially parallel to the lower surface of the grinding wheel 1642.

[0041] Next, the grinding unit 16 is moved in the X-axis direction by the X-axis moving unit 18 shown in FIGS. 1 and 3, and the center of the holding surface 302 of the chuck table 3 (i.e., the center of the plate-shaped workpiece 90) is located on a straight line extending in the virtual Y-axis direction passing through the center of the grinding wheel 164. Thus, alignment in the X-axis direction between the grinding unit 16 and the chuck table 3 is performed.

[0042] Next, the motor 132 of the horizontal movement unit 13 repeatedly rotates the ball screw 130 by a predetermined angle and then stops for a certain period of time, so that the chuck table 3 moves a predetermined distance in the Y-axis direction and then stops, and after a predetermined time elapses, it moves a predetermined distance in the Y-axis direction again to perform step movement.

[0043] The end-side region on the +Y direction side of the upper surface 904 of the plate-shaped workpiece 90 sucked and held by the chuck table 3 that performs step movement in the +Y direction by the horizontal movement unit 13 is positioned below the grinding wheel 1642, and the movement of the chuck table 3 stops once. Next, when the grinding unit 16 is lowered in the -Z direction at a predetermined grinding feed rate by the lifting unit 17, the grinding wheel 1642 that rotates at a predetermined rotational speed contacts the upper surface 904 of the plate-shaped workpiece 90.

[0044] At this time, in the present embodiment, the holding surface 302 cuts into the upper surface 904 of the plate-shaped workpiece 90 held by the holding surface 302 from the lower surface (flat surface) of the grinding wheel 1642. And by not rotating the holding surface 302 of the chuck table 3, an arc-shaped groove 907 shown in FIG. 4 is formed on the upper surface 904 of the plate-shaped workpiece 90. For example, the width of the arc-shaped groove 907 is approximately the same as the blade width of the grinding wheel 1642.

[0045] After the grinding wheel 1642 shown in FIG. 3 cuts into the upper surface 904 to a position at a predetermined height above the finish thickness of the plate-shaped workpiece 90 and forms an arc-shaped groove 907 shown in FIG. 4 with a predetermined depth, the grinding unit 16 is lifted by the lifting unit 17, and the grinding wheel 1642 is separated from the plate-shaped workpiece 90 once.

[0046] (2-1) Grinding wheel movement process after the arc groove forming process of Embodiment 1 Next, in order to position the grinding wheel 1642 at a position different from the position of the grinding wheel 1642 positioned with respect to the plate-shaped workpiece 90 in the arc groove forming process of Embodiment 1, at least one of the grinding wheel 1642 and the chuck table 3 is moved relatively in the horizontal direction, which is a direction parallel to the holding surface 302. In this embodiment, the chuck table 3 step-moves a predetermined distance in the +Y direction by the horizontal movement unit 13 shown in FIG. 3, so that the grinding wheel 1642 of the grinding unit 16 is positioned above the region where the groove 907 on the upper surface 904 of the plate-shaped workpiece 90 held and attracted to the holding surface 302 has not yet been formed.

[0047] (3-1) Multiple groove forming processes repeating the arc groove forming process and the grinding wheel movement process of Embodiment 1 After the grinding wheel 1642 is newly positioned in the Y-axis direction with respect to the upper surface 904 of the plate-shaped workpiece 90, again, the grinding unit 16 is lowered in the -Z direction at a predetermined grinding feed rate by the lifting unit 17 shown in FIG. 3, and the rotating grinding wheel 1642 cuts into the upper surface 904 of the plate-shaped workpiece 90 by a predetermined depth from the lower surface which is a flat surface, and the second arc groove 907 shown in FIG. 4 is formed. Then, the same grinding wheel movement process as described above is performed. In this way, by repeating the arc groove forming process and the grinding wheel movement process, a plurality of arc-shaped grooves 907 are formed on the upper surface 904 of the plate-shaped workpiece 90 from the +Y direction side to the -Y direction side of the upper surface 904 of the plate-shaped workpiece 90. As a result, for example, as shown in FIGS. 5 and 6, a plurality of arc grooves 907 are formed on substantially the entire upper surface 904 of the plate-shaped workpiece 90 at substantially equal intervals in the advancing direction (Y-axis direction) of the plate-shaped workpiece 90.

[0048] Then, even when the grinding wheel 1642 is continuously brought into contact with the upper surface 904 of the plate-shaped workpiece 90 held by suction on the holding surface 302 while the curvature of the plate-shaped workpiece 90 is corrected by the grooves 907 of the plurality of arcs and the plate-shaped workpiece 90 is ground while rotating with the rotation of the chuck table 3, the curvature of the plate-shaped workpiece 90 is restored during grinding due to the frictional force acting between the grinding wheel 1642 and the upper surface 904 of the plate-shaped workpiece 90, and no vacuum leak or the like will occur.

[0049] (1-2) Embodiment 2 of the arc groove forming process For example, instead of the arc groove forming process of Embodiment 1, the arc groove forming process of Embodiment 2 described below may be implemented. In the arc groove forming process of Embodiment 2, for example, the inclination of the holding surface 302 of the chuck table 3 with respect to the lower surface of the grinding wheel 1642 is relatively changed, and the holding surface 302 cuts into the upper surface 904 of the plate-shaped workpiece 90 held by the holding surface 302 from the outer peripheral angle of the lower surface of the grinding wheel 1642. That is, an arc groove is formed by the outer blade of the grinding wheel 1642.

[0050] Specifically, when the inclination of the chuck table 3 is adjusted by the inclination adjustment unit 37 shown in FIG. 7 and the traveling direction of the chuck table 3 with respect to the grinding wheel 1642 of the plate-shaped workpiece 90 held by suction on the chuck table 3 is set as the +Y direction, the entire chuck table 3 is tilted so that the front side (+Y direction side) of the chuck table 3 is lower than the rear side (-Y direction side) of the chuck table 3.

[0051] Next, the grinding unit 16 is moved in the X-axis direction by the X-axis moving unit 18 shown in FIG. 7, and the alignment in the X-axis direction between the grinding unit 16 and the chuck table 3 is performed so that the region on the -X direction side (the back side of the paper surface) of the upper surface 904 of the plate-shaped workpiece 90 held by suction on the holding surface 302 of the chuck table 3 is located on a virtual straight line extending in the Y-axis direction passing through the center of the grinding wheel 164.

[0052] The end side region on the +Y direction side of the upper surface 904 of the plate-shaped workpiece 90 sucked and held by the chuck table 3 that is step-moved in the +Y direction by the horizontal movement unit 13 is positioned below the grinding wheel 1642 of the grinding unit 16, and the movement of the chuck table 3 stops once. Then, when the grinding unit 16 descends in the -Z direction at a predetermined grinding feed rate, the grinding wheel 1642 rotating at a predetermined rotational speed cuts into the upper surface 904 of the plate-shaped workpiece 90. At this time, in this embodiment, it cuts into the upper surface 904 of the plate-shaped workpiece 90 held by the holding surface 302 from the outer peripheral angle (outer blade) of the lower surface of the grinding wheel 1642. And by not rotating the holding surface 302 of the chuck table 3, an arc-shaped groove 908 shown in FIG. 8 is formed in the region on the -X direction side of the upper surface 904 of the plate-shaped workpiece 90.

[0053] After the grinding wheel 1642 cuts into the upper surface 904 from the outer blade to a position at a predetermined height above the finish thickness of the plate-shaped workpiece 90 and an arc-shaped groove 908 of a predetermined depth is formed, the grinding wheel 1642 rises and separates from the plate-shaped workpiece 90 once.

[0054] (2-2) Grinding wheel movement step after the arc groove forming step of Embodiment 2 Next, in order to position the grinding wheel 1642 at a position different from the position of the grinding wheel 1642 positioned with respect to the plate-shaped workpiece 90 in the arc groove forming step of Embodiment 2, the grinding wheel 1642 and the chuck table 3 are relatively moved horizontally. For example, by the horizontal movement unit 13 shown in FIG. 7, the chuck table 3 step-moves a predetermined distance in the +Y direction, so that the grinding wheel 1642 of the grinding unit 16 is positioned above the region where the groove 908 has not yet been formed in the region on the -X direction side of the upper surface 904 of the plate-shaped workpiece 90 sucked and held by the holding surface 302.

[0055] (3-2) Multiple groove forming steps of repeating the arc groove forming step and the grinding wheel movement step of Embodiment 2 After the new positioning of the grinding wheel 1642 in the Y-axis direction, again, the grinding unit 16 descends in the -Z direction at a predetermined grinding feed rate, and the rotating grinding wheel 1642 cuts into the upper surface 904 of the plate-shaped workpiece 90 by a predetermined depth from the outer edge on the lower surface, forming the second arc-shaped groove 908 shown in FIG. 8. Then, the same grinding wheel movement process as described above is carried out. By repeating the arc groove forming process and the grinding wheel movement process in this way, a plurality of arc-shaped grooves 908 are sequentially formed from the +Y direction side to the -Y direction side in substantially the entire region on the -X direction side of the upper surface 904 of the plate-shaped workpiece 90.

[0056] For example, after a plurality of arc grooves 908 shown in FIG. 8 are sequentially formed from the +Y direction side to the -Y direction side in substantially the entire region on the -X direction side of the upper surface 904 of the plate-shaped workpiece 90, the grinding unit 16 is moved in the +X direction by the X-axis moving unit 18 shown in FIG. 7, and on a straight line extending in the virtual Y-axis direction passing through the center of the grinding wheel 164, the +X direction side of the upper surface 904 of the plate-shaped workpiece 90 held and attracted on the holding surface 302 is positioned so that the region where the groove 908 has not been formed is located. Alignment in the X-axis direction between the grinding unit 16 and the chuck table 3 is performed.

[0057] Then, by repeating the arc groove forming process and the grinding wheel movement process of Embodiment 2 described above again, a plurality of arc grooves 908 are sequentially formed from the +Y direction side to the -Y direction side in substantially the entire region on the -X direction side of the upper surface 904 of the plate-shaped workpiece 90. In this embodiment, since the curvature of the central region is smaller than that of both the +X direction side and -X direction side regions of the upper surface 904 of the plate-shaped workpiece 90 where the arc grooves 908 are formed, in the example shown in FIG. 8, the plurality of groove forming processes are completed without forming the grooves 908. However, further, as shown in FIG. 9, a plurality of arc grooves 908 may also be formed in the central region of the upper surface 904. In particular, since the four corner portions of the plate-shaped workpiece 90 are greatly curved, it is preferable that arc grooves 908 are formed in the four corner portions after the plurality of groove forming processes. Also, the arc grooves 908 may be formed so that the arc grooves 908 intersect each other. Then, due to the grooves 908 of the plurality of arcs, the curvature of the plate-shaped workpiece 90 is corrected.

[0058] (1 - 3) Embodiment 3 of the arc groove forming process For example, instead of the arc groove forming process of Embodiment 1, the arc groove forming process of Embodiment 3 described below may be performed. In the arc groove forming process of Embodiment 3, for example, the inclination of the chuck table 3 is adjusted by the inclination adjustment unit 37 shown in FIG. 3, and the upper surface 904 of the plate-shaped workpiece 90 held by suction on the holding surface 302 becomes substantially parallel to the lower surface of the grinding wheel 1642. Further, it is provided with a table rotation mechanism 33 for rotating the chuck table 3 about the center of the chuck table 3.

[0059] Next, the chuck table 3 holding the plate-shaped workpiece 90 is moved by the horizontal movement unit 13 shown in FIG. 3 to below the grinding unit 16, and the grinding unit 16 is moved in the X-axis direction by the X-axis movement unit 18 to align the grinding wheel 164 and the plate-shaped workpiece 90. In this alignment, for example, the rotation center of the grinding wheel 1642 is horizontally displaced by a predetermined distance with respect to the center of the holding surface 302 of the chuck table 3 (that is, the center of the upper surface 904 of the plate-shaped workpiece 90).

[0060] After the above alignment is performed, when the grinding unit 16 descends at a predetermined grinding feed rate, the rotating grinding wheel 1642 contacts the upper surface 904 of the plate-shaped workpiece 90. Then, it cuts into the upper surface 904 of the plate-shaped workpiece 90 held by the holding surface 302 from the lower surface (flat surface) of the grinding wheel 1642. Also, by not rotating the holding surface 302 of the chuck table 3, a single arc groove 909 passing through the center of the upper surface 904 of the plate-shaped workpiece 90 and one or two of the four corner regions is formed.

[0061] The grinding wheel 1642 cuts into the upper surface 904 up to a position at a predetermined height above the finishing thickness for finishing the plate-shaped workpiece 90 in the grinding process, and after an arc-shaped groove 909 with a predetermined depth shown in FIG. 10 is formed, the grinding unit 16 rises in the +Z direction, and the grinding wheel 1642 is separated from the plate-shaped workpiece 90 once.

[0062] (2-3) Grinding wheel movement process after the arc groove forming process of Embodiment 3 Next, after the table rotation mechanism 33 rotates the chuck table 3 by a predetermined angle and then stops the rotation, the grinding wheel 1642 is positioned at a position different from the position of the grinding wheel 1642 positioned with respect to the plate-shaped workpiece 90 in the arc groove forming process of Embodiment 3. The positional movement of the plate-shaped workpiece 90 with respect to the grinding wheel 1642 is performed such that the rotation locus of the grinding wheel 1642 passes through the arc-shaped groove 909 that forms at least one to two of the four corner regions of the upper surface 904 of the plate-shaped workpiece 90. Further, the grinding wheel 1642 may be positioned with respect to the plate-shaped workpiece 90 such that the rotation locus of the grinding wheel 1642 passes through the center of the plate-shaped workpiece 90.

[0063] (3-3) Multiple groove forming process for repeating the arc groove forming process and the grinding wheel movement process of Embodiment 3 The grinding wheel 1642 is positioned above the plate-shaped workpiece 90, and by rotating the chuck table 3 by a predetermined angle, a new positioning of the grinding wheel 1642 with respect to the upper surface 904 of the plate-shaped workpiece 90 is performed. Then, again, the grinding unit 16 descends at a predetermined grinding feed rate, and the rotating grinding wheel 1642 cuts into the upper surface 904 of the plate-shaped workpiece 90 by a predetermined depth from the lower surface, and the second arc-shaped groove 909 shown in FIG. 10 is formed. And then, the same grinding wheel movement process as described above is performed. In this way, by repeating the arc groove forming process and the grinding wheel movement process of Embodiment 3 a plurality of times, the arc-shaped grooves 909 are formed so as to intensively pass through the four corner regions of the upper surface 904 of the plate-shaped workpiece 90, that is, the regions with a stronger degree of curvature. And by completing the multiple groove forming process, the curvature of the plate-shaped workpiece 90 is corrected by the plurality of arc-shaped grooves 909.

[0064] (1-4) Embodiment 4 of the arc groove forming process For example, instead of the arc groove forming process of Embodiment 1, the arc groove forming process of Embodiment 4 described below may be implemented. In the arc groove forming process of Embodiment 4, for example, the inclination of the holding surface 302 of the chuck table 3 with respect to the lower surface of the grinding wheel 1642 having a diameter larger than at least the size of the plate-like workpiece 90 is relatively changed, and the holding surface 302 of the chuck table 3 cuts into the upper surface 904 of the plate-like workpiece 90 held by the chuck table 3 from the inner peripheral angle of the lower surface of the grinding wheel 1642. That is, an arc groove is formed by the inner blade of the grinding wheel 1642.

[0065] Specifically, when the inclination of the chuck table 3 is adjusted by the inclination adjustment unit 37 shown in FIG. 11, and the traveling direction of the plate-like workpiece 90 held by the chuck table 3 with respect to the grinding wheel 1642 is the +Y direction, the entire chuck table 3 is tilted so that the front side (+Y direction side) of the chuck table 3 is higher than the rear side (-Y direction side) of the chuck table 3.

[0066] Next, the grinding unit 16 shown in FIG. 11 is moved in the X-axis direction, and alignment in the X-axis direction between the grinding unit 16 and the chuck table 3 is performed so that the center of the plate-like workpiece 90 on the holding surface 302 of the chuck table 3 is located on a virtual straight line extending in the Y-axis direction passing through the center of the grinding wheel 164.

[0067] Thereafter, for example, the end region on the +Y direction side of the upper surface 904 of the plate-like workpiece 90 held by the chuck table 3 by the horizontal movement unit 13 is positioned below the grinding wheel 1642 of the grinding unit 16, and the step movement of the chuck table 3 stops once. Then, when the grinding unit 16 descends in the -Z direction at a predetermined grinding feed rate, the grinding wheel 1642 rotating at a predetermined rotational speed contacts the upper surface 904 of the plate-like workpiece 90.

[0068] Then, the grinding wheel 1642 cuts into the upper surface 904 of the plate-shaped workpiece 90 held by the holding surface 302 from the inner circumferential angle (inner blade) side of the lower surface. By not rotating the holding surface 302 of the chuck table 3, as shown in FIG. 12, an arc-shaped groove 906 is formed in both regions on the ±X direction sides of the upper surface 904 of the plate-shaped workpiece 90. At this time, since the grinding wheel 1642 does not contact the central region in the X-axis direction of the upper surface 904 of the plate-shaped workpiece 90, an arc-shaped groove 906 is not formed in the central region.

[0069] After the grinding wheel 1642 cuts into the upper surface 904 from the inner blade side to a position at a predetermined height above the finish thickness of the plate-shaped workpiece 90 to form an arc-shaped groove 906 with a predetermined depth, the grinding wheel 1642 rises and separates from the plate-shaped workpiece 90 once.

[0070] (2-4) Grinding wheel movement step after the arc groove forming step of Embodiment 4 Next, the grinding wheel 1642 is relatively moved horizontally to a position different from the position of the grinding wheel 1642 positioned with respect to the plate-shaped workpiece 90 in the arc groove forming step of Embodiment 4. Specifically, the chuck table 3 step-moves a predetermined distance in the +Y direction, and the grinding wheel 1642 of the grinding unit 16 is positioned above the regions in both the ±X direction sides of the upper surface 904 of the plate-shaped workpiece 90 where the groove 906 has not yet been formed.

[0071] (3-4) Multiple groove forming steps of repeating the arc groove forming step and the grinding wheel movement step of Embodiment 4 Again, the grinding unit 16 descends at a predetermined grinding feed rate, and the rotating grinding wheel 1642 cuts into the upper surface 904 of the plate-shaped workpiece 90 by a predetermined depth from the inner circumferential angle side of the lower surface, and the second arc-shaped groove 906 is formed in both regions on the ±X direction sides of the upper surface 904. Then, the same grinding wheel movement step as before is performed. In this way, by repeating the arc groove forming step and the grinding wheel movement step of Embodiment 4, a plurality of arc-shaped grooves 906 are sequentially formed from the +Y direction side to the -Y direction side in both regions on the ±X direction sides of the upper surface 904 of the plate-shaped workpiece 90.

[0072] The plate-shaped workpiece 90 with a greater curvature on the outer peripheral side is in a state where the curvature is corrected by the plurality of arc-shaped grooves 906 shown in FIG. 12 after the plurality of groove forming steps. When the inner diameter of the grinding wheel 1642 is smaller than the length of the plate-shaped workpiece 90, just moving the chuck table 3 one span in the +Y direction from the +Y direction to the -Y direction as shown in FIG. 12 is not enough to form the arc-shaped grooves 906 on the entire regions on both the ±X direction sides of the upper surface 904 after the grinding wheel 1642 passes through the central region of the plate-shaped workpiece 90 in the Y-axis direction. Therefore, as shown in FIG. 13, arc-shaped grooves 9066 are formed on the plate-shaped workpiece 90 in halves. Such arc-shaped grooves 9066 are formed at equal intervals by stepwise moving the chuck table 3 in the +Y direction for one region bisected in the Y-axis direction (the moving direction of the chuck table 3) with respect to the center of the upper surface 904 of the plate-shaped workpiece 90 to form half of the arc-shaped grooves 9066, then rotating the chuck table 3 by 180 degrees, and forming the remaining half of the arc-shaped grooves 9066 on almost the entire other region while stepwise moving the chuck table 3. Or, after forming half of the arc-shaped grooves 9066, the inclination of the chuck table 3 is changed to form the remaining arc-shaped grooves 9066. Also, by performing the arc groove forming step, the grinding wheel moving step, and the plurality of groove forming steps of Embodiment 4, for example, it becomes possible not to consume the outer edge of the grinding wheel 1642 at the stage before starting creep feed grinding, for example, in the next grinding step.

[0073] (4-1) Grinding step of performing infeed grinding After the plurality of groove forming steps are completed, the plurality of arc-shaped grooves 907 shown in FIG. 5, the plurality of arc-shaped grooves 908 shown in FIG. 8, the plurality of arc-shaped grooves 909 shown in FIG. 10, or the plurality of arc-shaped grooves 906 shown in FIG. 12 formed on the upper surface 904 of the plate-shaped workpiece 90 are removed by grinding the upper surface 904, and the plate-shaped workpiece 90 is ground to a predetermined thickness. For example, this grinding is infeed grinding.

[0074] For example, the inclination of the chuck table 3 is adjusted by the inclination adjustment unit 37 shown in FIGS. 1 and 3, so that the upper surface 904 of the plate-shaped workpiece 90 sucked and held on the holding surface 302 becomes substantially parallel to the lower surface of the grinding wheel 1642. Next, the horizontal movement unit 13 moves the chuck table 3 that sucks and holds the plate-shaped workpiece 90 under the grinding unit 16, and the rotation center of the grinding wheel 1642 is horizontally displaced by a predetermined distance with respect to the center of the upper surface 904 of the plate-shaped workpiece 90 sucked and held on the holding surface 302, and alignment is performed so that the rotation locus of the grinding wheel 1642 passes through the center of the plate-shaped workpiece 90.

[0075] After the above alignment is performed, when the grinding unit 16 descends at a predetermined grinding feed rate, the grinding wheel 1642 rotating at a predetermined rotational speed contacts the upper surface 904 of the plate-shaped workpiece 90. In addition, as the chuck table 3 rotates at a predetermined rotational speed, for example, in the same direction as the rotational direction of the grinding wheel 1642, the plate-shaped workpiece 90 held on the holding surface 302 also rotates, so that the grinding wheel 1642 performs grinding on the entire upper surface 904 of the plate-shaped workpiece 90.

[0076] Since the curvature of the plate-shaped workpiece 90 is pre-corrected by the plurality of arc-shaped grooves 907 shown in FIG. 5 formed on the upper surface 904, the plurality of arc-shaped grooves 908 shown in FIG. 8, the plurality of arc-shaped grooves 909 shown in FIG. 10, the plurality of arc-shaped grooves 906 shown in FIG. 12, or the plurality of arc-shaped grooves 9066 shown in FIG. 13, during the grinding process of thinning the plate-shaped workpiece 90, the curvature of the plate-shaped workpiece 90 will not be restored, and the situation where the plate-shaped workpiece 90 separates from the holding surface 302 and a vacuum leak occurs will not occur.

[0077] While measuring the thickness of the plate-shaped workpiece 90 being ground by the thickness measurement unit 104 shown in FIGS. 1 and 3, and while the upper surface 904 of the plate-shaped workpiece 90 is being ground, the plurality of arc-shaped grooves 907 shown in FIG. 5, the plurality of arc-shaped grooves 908 shown in FIG. 8, the plurality of arc-shaped grooves 909 shown in FIG. 10, the arc-shaped groove 906 shown in FIG. 12, or the plurality of arc-shaped grooves 9066 shown in FIG. 13 formed on the upper surface 904 are being removed, and the upper surface 904 of the plate-shaped workpiece 90 is being formed into a flat surface. Then, when the plate-shaped workpiece 90 is ground to a desired thickness, the grinding unit 16 rises, the grinding wheel 1642 disengages from the plate-shaped workpiece 90, and the grinding process ends.

[0078] (4-2) Grinding process for performing creep feed grinding Instead of infeed grinding, the plurality of arc-shaped grooves 907 shown in FIG. 5, the plurality of arc-shaped grooves 908 shown in FIG. 8, the plurality of arc-shaped grooves 909 shown in FIG. 10, the plurality of arc-shaped grooves 906 shown in FIG. 12, or the plurality of arc-shaped grooves 9066 shown in FIG. 13 formed on the upper surface 904 of the plate-shaped workpiece 90 may be removed by grinding the upper surface 904, and the plate-shaped workpiece 90 may be creep feed ground to a predetermined thickness.

[0079] For example, first, the lifting unit 17 causes the grinding unit 16 to descend until the height position of the lower surface of the grinding wheel 1642 reaches the height position for making the plate-shaped workpiece 90 have a desired thickness (finish thickness). Also, the inclination adjustment unit 37 shown in FIGS. 1 and 3 adjusts the inclination of the chuck table 3, so that the upper surface 904 of the plate-shaped workpiece 90 suction-held on the holding surface 302 becomes substantially parallel to the lower surface of the grinding wheel 1642.

[0080] Then, while the grinding wheel 164 rotates at a predetermined rotational speed, the horizontal movement unit 13 shown in FIG. 1 moves the chuck table 3 that suction-holds the plate-shaped workpiece 90, for example, in the +Y direction at a low speed, so that the upper surface 904 of the plate-shaped workpiece 90 is ground mainly by the outer surface of the rotating grinding wheel 1642.

[0081] Since the bending of the plate-shaped workpiece 90 has been corrected in advance by a plurality of arc-shaped grooves 907 shown in FIG. 5 formed on the upper surface 904, a plurality of arc-shaped grooves 908 shown in FIG. 8, a plurality of arc-shaped grooves 909 shown in FIG. 10, a plurality of arc-shaped grooves 906 shown in FIG. 12, or a plurality of arc-shaped grooves 9066 shown in FIG. 13, a situation where the bending of the plate-shaped workpiece 90 is restored during the creep feed grinding process and the plate-shaped workpiece 90 separates from the holding surface 302, resulting in a vacuum leak, does not occur.

[0082] By the above grinding, a plurality of arc-shaped grooves 907 shown in FIG. 5 formed on the upper surface 904, a plurality of arc-shaped grooves 908 shown in FIG. 8, a plurality of arc-shaped grooves 909 shown in FIG. 10, the arc-shaped groove 906 shown in FIG. 12, or a plurality of arc-shaped grooves 9066 shown in FIG. 13 are removed, and the upper surface 904 of the plate-shaped workpiece 90 is formed into a flat surface. Then, the chuck table 3 moves to a predetermined position in the Y-axis direction where the grinding wheel 1642 has passed over the upper surface 904 of the plate-shaped workpiece 90, and the entire upper surface 904 of the plate-shaped workpiece 90 is ground by the grinding wheel 1642.

[0083] As described above, in the method for grinding a plate-shaped workpiece 90 according to the present invention, in which the upper surface 904 of a curved plate-shaped workpiece 90 having a force in the direction (+Z direction) in which the outer peripheral portion held by the holding surface 302 of the chuck table 3 separates from the holding surface 302 is ground with an annular grinding wheel 1642, the chuck table 3 holds the plate-shaped workpiece 90 on the holding surface 302, and the grinding wheel 1642 positioned above the plate-shaped workpiece 90 held on the holding surface 302 is lowered in a direction perpendicular to the holding surface 302, and the grinding wheel 1642 is cut into the upper surface 904 of the plate-shaped workpiece 90 without rotating the holding surface 302 to form an arc-shaped groove; an arc groove forming step; a grinding wheel moving step of moving at least one of the grinding wheel 1642 and the chuck table 3 relatively in a direction parallel to the holding surface 302 in order to position the grinding wheel 1642 at a position different from the position of the grinding wheel 1642 positioned with respect to the plate-shaped workpiece 90 in the arc groove forming step; and a plurality of groove forming steps of repeating the arc groove forming step and the grinding wheel moving step to form a plurality of grooves on the upper surface 904 of the plate-shaped workpiece 90 to correct the curvature of the plate-shaped workpiece 90. By providing these steps, before grinding and thinning the plate-shaped workpiece 90, the force with which the plate-shaped workpiece 90 tends to separate from the holding surface 302 is reduced by forming a plurality of grooves. Thus, while removing the grooves by grinding the upper surface 904 of the plate-shaped workpiece 90, the occurrence of vacuum leakage is prevented by ensuring that the plate-shaped workpiece 90 does not separate from the holding surface 302, and the plate-shaped workpiece 90 can be ground to a predetermined thickness. Further, since the formation process and the grinding process of a plurality of grooves are carried out only with the grinding wheel 1642, the types of grinding wheels can be reduced, and it is not necessary to have an inventory of a plurality of types of grinding wheels in the grinding apparatus 1.

[0084] The method for grinding a plate-shaped workpiece according to the present invention is not limited to the above-described embodiment, and it goes without saying that it may be implemented in various different forms within the scope of the technical idea. Also, the configuration of the grinding apparatus 1 shown in FIG. 1 used when implementing the grinding method can be appropriately changed within the range in which the effects of the present invention can be exhibited.

Explanation of Reference Numerals

[0085] 90: Plate-shaped workpiece 904: Upper surface of the plate-shaped workpiece 902: Lower surface of the plate-shaped workpiece 9000: Protective tape 1: Grinding device 10: Device base 13: Horizontal movement unit 130: Ball screw 132: Motor 3: Chuck table 30: Porous part 302: Holding surface 31: Frame body 37: Tilt adjustment part 371: Piston rod 35: Chuck base 11: Column 17: Lifting unit 170: Ball screw 172: Motor 16: Grinding unit 160: Rotation axis 162: Motor 164: Grinding wheel 1641: Wheel base 1642: Grinding stone 104: Thickness measurement part 4: Pressing mechanism 44: Pressing pad 41: Arm part 40: Lifting mechanism 45: Swivel axis

Claims

A grinding apparatus comprising a chuck table having a holding surface, a horizontal movement unit for horizontally moving the chuck table in a direction parallel to the holding surface, a grinding unit including a plurality of grinding wheels arranged in a ring shape, and a lifting unit for lifting and lowering the grinding unit in a direction perpendicular to the holding surface, is used. A method for grinding a plate-shaped workpiece, which grinds the upper surface of the plate-shaped workpiece having a force in a direction away from the holding surface of the chuck table with an annular grinding wheel. Press the entire lower surface of the plate-shaped workpiece against the holding surface, hold the plate-shaped workpiece on the holding surface in a state where the curvature is temporarily eliminated, and lower the grinding wheel positioned above the plate-shaped workpiece held on the holding surface in a direction perpendicular to the holding surface by the lifting unit, and cut the grinding wheel into the upper surface of the plate-shaped workpiece without rotating the holding surface to form an arc-shaped groove; an arc groove forming step. A table movement step in which the horizontal movement unit moves the chuck table in a direction parallel to the holding surface so as to position the grinding wheel at a position different from the position of the grinding wheel positioned with respect to the plate-shaped workpiece in the arc groove forming step. A plurality of groove forming steps in which the arc groove forming step and the table movement step are repeated to form a plurality of the grooves on the upper surface of the plate-shaped workpiece to correct the curvature of the plate-shaped workpiece. A method for grinding a plate-shaped workpiece, comprising: after forming a plurality of the grooves, grinding the upper surface of the plate-shaped workpiece with the grinding wheel to remove the grooves, and grinding the plate-shaped workpiece to a predetermined thickness; a grinding step. Claim 2 The grinding step rotates the chuck table about the center of the holding surface, and lowers the grinding wheel passing through the rotation center of the plate-shaped workpiece held on the rotating holding surface in a direction perpendicular to the holding surface by the lifting unit to bring the lower surface of the grinding wheel into contact with the plate-shaped workpiece, and grinds the plate-shaped workpiece. The method for grinding a plate-shaped workpiece according to claim 1. Claim 3 The grinding step positions the lower surface of the grinding wheel outside the outer periphery of the plate-shaped workpiece held on the holding surface and below the upper surface of the plate-shaped workpiece, horizontally moves the chuck table by the horizontal movement unit, and grinds the plate-shaped workpiece. The method for grinding a plate-shaped workpiece according to claim 1. Claim 4 The arc groove forming step is the method for grinding a plate-shaped workpiece according to claim 1, claim 2, or claim 3, wherein the chuck table is tilted such that the front side in the advancing direction is lower than the rear side, and the lower surface outer peripheral corner of the grinding wheel is cut into the upper surface of the plate-shaped workpiece held by the holding surface.

5. The arc groove forming step is the method for grinding a plate-shaped workpiece according to claim 1, claim 2, or claim 3, wherein the chuck table is tilted such that the front side in the advancing direction is higher than the rear side, and the lower surface inner peripheral corner of the grinding wheel is cut into the upper surface of the plate-shaped workpiece held by the holding surface.

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