How to shape the holding table

Abstract

To provide a method for forming a holding table which is effective for adjusting flatness of a work-piece to a desired value by grinding the work-piece.SOLUTION: A holding table is temporarily fixed to a table base first (a temporarily fixing step) prior to grinding a surface side of the holding table (self-grinding). A rear-back surface of the holding table is suctioned by operating a suction source with a front surface of the holding table sealed with a sealing material, so as to tightly attach the rear surface of the holding table to a surface to be placed of the table base (a tightly attaching step), and then the holding table is fixed to the table base (a fixing step).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for shaping a holding table, which grinds the front surface side of a holding table to shape the surface of the holding table. [Background technology]

[0002] Chips of devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are essential components in various electronic devices such as mobile phones and personal computers. Such chips are manufactured, for example, by dividing a workpiece such as a wafer having a large number of devices formed on its surface into areas each including an individual device.

[0003] Furthermore, the workpiece is often thinned before being divided in order to reduce the size and weight of the chips. One method for thinning the workpiece is to grind the workpiece in a grinding device. In this grinding device, the workpiece is ground by contacting the grinding wheels with the workpiece while rotating the workpiece and a grinding wheel on which multiple grinding wheels are arranged in a circular ring shape.

[0004] Specifically, in the grinding device, the workpiece is ground while rotating a holding table that holds the workpiece. This holding table is generally composed of a disk-shaped porous plate exposed on the surface of the holding table and a disk-shaped frame body in which a recess into which the porous plate fits is formed.

[0005] Furthermore, the frame is formed with a through hole that opens at the bottom surface of the recess, and the through hole can be connected to a suction source. When the suction source is operated, a suction force acts on the surroundings from the surface of the holding table via the porous plate. Therefore, by operating the suction source with the workpiece placed on the surface of the holding table, the workpiece can be held on the holding table.

[0006] Furthermore, the grinding device is generally provided with a table base having a support surface on which the back surface of the holding table is placed, and the holding table is fixed to the table base using fixing devices such as bolts. In other words, the holding table is generally detachable from the grinding device.

[0007] Furthermore, a drive shaft is fixed to the surface of the table base opposite the workpiece surface on which the workpiece is placed. By rotating the drive shaft while the holding table is fixed to the table base, the workpiece held on the holding table can be rotated.

[0008] Incidentally, in such a grinding device, prior to grinding the workpiece, grinding (self-grinding) the surface side of the holding table is sometimes performed to shape the surface (see, for example, Patent Document 1). This makes it possible to improve the flatness (total thickness variation: TTV) of the workpiece that is ground while held on the holding table. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2008-114336 A Summary of the Invention [Problem to be solved by the invention]

[0010] However, the state of the holding table during self-grinding (the former state) is different from the state of the holding table during grinding of the workpiece (the latter state). For example, in the former state, grinding is performed with the porous plate of the holding table exposed without operating the suction source, whereas in the latter state, grinding is performed with the suction source operating and applying suction force to the workpiece placed on the holding table.

[0011] Due to this difference, in the former situation, the gap between the back surface of the holding table and the support surface of the table base may be wider than the gap between the two surfaces in the latter situation. As a result, even if the holding table is self-ground, it may be difficult to achieve the desired flatness of the workpiece when grinding the workpiece.

[0012] In view of this, an object of the present invention is to provide a method for shaping a holding table which is effective for achieving a desired flatness of a workpiece by grinding the workpiece. [Means for solving the problem]

[0013] According to the present invention, in a grinding device including a table base having a mounting surface on which a back surface of a holding table having a surface on which a workpiece is placed is placed, a drive shaft fixed to the surface side of the table base opposite the mounting surface, a rotation unit which rotates the table base via the drive shaft, a suction source capable of sucking the workpiece placed on the surface of the holding table toward the holding table and of sucking the holding table placed on the mounting surface of the table base toward the table base, and a spindle to the tip of which can be attached a grinding wheel having a plurality of grinding stones arranged discretely in an annular shape, the method for shaping the front surface of the holding table by grinding the front surface side of the holding table includes a mounting step of placing the back surface of the holding table on the mounting surface of the table base, and a fixing tool for fixing the holding table after the mounting step, the method including: a temporary fixing step of temporarily fixing the holding table to the table base with a fixing force smaller than a predetermined fixing force required for sealing the front surface of the holding table with a sealing material, and a contact step of operating the suction source after the temporary fixing step to suck the back surface of the holding table and bring the back surface of the holding table and the support surface of the table base into close contact with each other; a fixing step of fixing the holding table to the table base with the predetermined fixing force using the fixing tool while the back surface of the holding table is still being sucked after the contact step; and a grinding step of rotating the table base via the drive shaft and bringing the grinding wheel into contact with the front surface of the holding table while rotating the grinding wheel via the spindle, with the sealing material removed from the front surface of the holding table after the fixing step, to grind the front surface side of the holding table. Effect of the Invention

[0014] In the present invention, prior to grinding the front surface side of the holding table (self-grinding), the holding table is first temporarily fixed to the table base (temporary fixing step). Then, with the front surface of the holding table sealed with a sealant, the suction source is operated to suck the rear surface of the holding table and bring the rear surface of the holding table and the receiving surface of the table base into close contact (contact step), and then the holding table is fixed to the table base (fixing step).

[0015] In this case, the gap between the underside of the holding table and the supporting surface of the table base during self-grinding of the holding table is narrower than when only the fixing step is performed without performing the temporary fixing step and the adhesion step.

[0016] This allows the state of the holding table during self-grinding to be closer to the state of the holding table during grinding of the workpiece, and as a result, with the holding table shaped according to the present invention, it becomes easier to grind the workpiece to a desired flatness. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view that illustrates an example of a grinding device. [Diagram 2] FIG. 2 is a schematic diagram showing a cross section of a table base and a cross section of a drive shaft. [Diagram 3] FIG. 3 is a cross-sectional view that illustrates a schematic view of the holding table. [Figure 4] FIG. 4 is a flow chart illustrating an example of a method for shaping the holding table. [Diagram 5] FIG. 5 is a diagram showing a schematic view of the placement step. [Figure 6] FIG. 6 is a diagram showing a schematic view of the provisional fixing step. [Figure 7] FIG. 7 is a diagram showing a schematic view of the adhesion step. [Figure 8] FIG. 8 is a diagram showing a schematic view of the fixing step. [Figure 9] FIG. 9 is a diagram showing a schematic view of the grinding step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view showing a schematic example of a grinding device. Note that the X-axis direction (front-back direction) and the Y-axis direction (left-right direction) shown in Fig. 1 are directions perpendicular to each other on a horizontal plane, and the Z-axis direction (up-down direction) is a direction (vertical direction) perpendicular to each of the X-axis direction and the Y-axis direction.

[0019] The grinding device 2 shown in Fig. 1 has a base 4 that supports each of the components. An opening 4a having a longitudinal portion extending along the X-axis direction is formed on the upper surface of the base 4. Inside this opening 4a, a ball screw type X-axis direction moving mechanism (not shown) and an X-axis moving table (not shown) whose position in the X-axis direction is adjusted by the X-axis direction moving mechanism are arranged.

[0020] A table cover 6 with a cylindrical through hole formed in the center is provided above the X-axis moving table. A drive shaft (not shown in FIG. 1) for rotating a table base (described later) is passed through this through hole. This drive shaft is connected to the X-axis moving table and can move along the X-axis together with the X-axis moving table.

[0021] Furthermore, bellows-shaped dust-proof and drip-proof covers 8 that cover the upper side of the X-axis direction moving mechanism and extend along the X-axis direction are provided in front and behind the table cover 6. When the X-axis moving table moves along the X-axis direction, the table cover 6 also moves along the X-axis direction together with the drive shaft that passes through a through hole formed in the table cover 6, and the dust-proof and drip-proof covers 8 expand and contract in accordance with the moving table cover 6.

[0022] In addition, a disk-shaped table base 10 is provided on the table cover 6. Figure 2 is a diagram that shows a cross section of the table base 10 and a cross section of a drive shaft fixed to the underside of the table base 10. In Figure 2, some of the components connected to the drive shaft are shown as blocks.

[0023] The table base 10 is made of a metal material such as stainless steel. A plurality of (e.g., 12) cylindrical screw holes 10a are formed on the upper surface of the outer periphery of the table base 10 at approximately equal intervals along the circumferential direction of the table base 10. Each of the plurality of screw holes 10a can be screwed into a threaded portion of a bolt (fixing tool) described later.

[0024] Furthermore, a plurality of (for example, two) annular grooves 10b having different diameters are formed in an area inside the screw hole 10a on the top surface of the table base 10. A plurality of communication passages 10c each extending toward the bottom surface of the table base 10 are formed in the bottom surface of the grooves 10b.

[0025] Furthermore, the communication passage 10c communicates with a communication passage 10d that extends radially from the center inside the table base 10 in planes parallel to the upper and lower surfaces of the table base 10. The communication passage 10d communicates with cylindrical through holes 10e that open in the upper and lower surfaces of the table base 10.

[0026] A drive shaft 12 is fixed to the underside of the table base 10. A communication passage 12a that communicates with a through hole 10e of the table base 10 is formed in the drive shaft 12. The communication passage 12a can also communicate with a suction source 16 such as a vacuum pump via a valve 14.

[0027] Furthermore, a rotation unit (not shown) is connected to the lower part of the drive shaft 12. This rotation unit includes, for example, a pulley and a motor, and rotates the table base 10 via the drive shaft 12. The rotation unit is also connected to an X-axis moving table that is arranged inside the opening 4a of the base 4 shown in Fig. 1, and can move along the X-axis direction together with the X-axis moving table.

[0028] In the grinding device 2, a disk-shaped holding table 18 is placed on the upper surface (support surface) of the table base 10. Fig. 3 is a cross-sectional view showing the holding table 18. The holding table 18 has a frame 20 made of, for example, ceramics. The frame 20 includes a disk-shaped bottom wall 20a having approximately the same diameter as the table base 10.

[0029] A plurality of (for example, 12) cylindrical through holes 20b, each opening on the upper and lower surfaces of the bottom wall 20a, are formed at approximately equal intervals along the circumferential direction of the bottom wall 20a on the outer periphery of the bottom wall 20a.

[0030] The number of through holes 20b is the same as the number of screw holes 10a formed in the upper surface of the table base 10. The diameter of the through holes 20b is slightly longer than the width of the threaded portion of a bolt (fixing tool) described later and shorter than the width of the head of the bolt.

[0031] In addition, an annular side wall 20c is provided in an area inside the through hole 20b on the upper surface of the bottom wall 20a. A step is formed on the inner surface of this side wall 20c so that the inner diameter of the lower part is shorter than the inner diameter of the upper part.

[0032] In other words, inside the side wall 20c, there are a first cylindrical space surrounded by the upper part of the side wall 20c, and a second cylindrical space 20d surrounded by the lower part of the side wall 20c and having a diameter shorter than that of the first cylindrical space.

[0033] A ceramic disk-shaped porous plate 22 is fixed to the side wall 20c in the first cylindrical space. The upper surface of the porous plate 22 (the surface of the holding table 18) is flat, but is shaped into a shape corresponding to the side surface of a cone, for example, by grinding (self-grinding) the upper surface side of the holding table 18, which will be described later.

[0034] Furthermore, a cylindrical through hole 20e is formed in the center of the bottom wall 20a, opening on both the upper and lower surfaces of the bottom wall 20a. The through hole 20e is formed so as to communicate with a through hole 10e formed in the table base 10 when the holding table 18 is placed on the upper surface of the table base.

[0035] 1, the remaining components of the grinding device 2 will be described. An operation panel 24 for inputting grinding conditions and the like is provided near the front end of the opening 4a formed in the upper surface of the base 4. In addition, a rectangular parallelepiped support structure 26 extending upward is provided near the rear end of the opening 4a.

[0036] A Z-axis direction moving mechanism 28 is provided on the front side (i.e., the operation panel 24 side) of this support structure 26. The Z-axis direction moving mechanism 28 has a pair of Z-axis guide rails 30 extending along the Z-axis direction. A Z-axis moving plate 32 is connected to the front side of the pair of Z-axis guide rails 30 in a manner that allows it to slide along the pair of Z-axis guide rails 30.

[0037] A screw shaft 34 extending along the Z-axis direction is disposed between the pair of Z-axis guide rails 30. A motor 36 for rotating the screw shaft 34 is connected to one end of the screw shaft 34. A nut portion (not shown) for accommodating balls that roll on the surface of the rotating screw shaft 34 is provided on the surface of the screw shaft 34 on which a spiral groove is formed, thereby forming a ball screw.

[0038] That is, when the screw shaft 34 rotates, the balls circulate inside the nut portion, causing the nut portion to move along the Z-axis direction. This nut portion is fixed to the rear surface side (back surface side) of the Z-axis moving plate 32. Therefore, when the screw shaft 34 is rotated by the motor 36, the Z-axis moving plate 32 moves along the Z-axis direction together with the nut portion.

[0039] A support 38 is provided on the front side of the Z-axis moving plate 32. This support 38 supports a grinding unit 40. The grinding unit 40 has a cylindrical spindle housing 42 fixed to the support 38. A columnar spindle 44 extending along the Z-axis direction is partially accommodated in this spindle housing 42 in a rotatable state.

[0040] A motor 46 for rotating the spindle 44 is connected to the upper end (base end) of the spindle 44. The lower end of the spindle 44 is exposed from the spindle housing 42, and a disk-shaped wheel mount 48 made of a metal material such as stainless steel is provided on this lower end (tip end).

[0041] An annular grinding wheel 50 having approximately the same diameter as the wheel mount 48 is attached to the lower part of the wheel mount 48. The grinding wheel 50 has an annular wheel base 52 made of a metal material such as stainless steel. A plurality of grinding stones 54 are fixed to the underside of the wheel base 52.

[0042] Each of the grinding wheels 54 has a rectangular parallelepiped shape and is arranged in a circular ring shape along the circumferential direction of the wheel base 52. Furthermore, a nozzle (not shown) is provided near or inside the grinding wheel 50 to supply a grinding fluid such as water to the grinding surface when grinding the workpiece. When the motor 46 operates, the grinding wheel 50 rotates together with the spindle 44 around a straight line along the Z-axis direction as a rotation axis.

[0043] Fig. 4 is a flow chart showing an example of a method for shaping the surface of the holding table 18 by grinding the front surface side of the holding table 18 in the grinding device 2. Also, Figs. 5 to 9 are each a diagram showing a schematic diagram of each of a plurality of steps included in the method shown in Fig. 4.

[0044] In this method, first, the lower surface (rear surface) of the holding table 18 is placed on the upper surface (support surface) of the table base 10 so that each of the multiple through holes 20b of the frame body 20 of the holding table 18 overlaps with one of the screw holes 10a of the table base 10 (placing step: S1) (see Figure 5).

[0045] Next, the holding table 18 is temporarily fixed to the table base 10 (temporary fixing step: S2) (see FIG. 6). Specifically, a bolt (fixing tool) 56 is inserted into each of the multiple through holes 20b of the holding table 18, and the bolt 56 is rotated in a direction in which the bolt 56 screws into the screw hole 10a of the table base 10.

[0046] At this time, the force (torque) (fixing force) for rotating the bolt 56 is set lower than the force for rotating the bolt 56 in the fixing step described below. For example, the force for rotating the bolt 56 in the temporary fixing step is 1 Nm.

[0047] Next, the lower surface (rear surface) of the holding table 18 and the upper surface (receiving surface) of the table base 10 are brought into close contact with each other (close contact step: S3) (see FIG. 7). Specifically, first, the upper surface of the holding table 18 is sealed with a disk-shaped sealing material 11 so as to cover at least the upper surface of the porous plate 22. The sealing material 11 is, for example, a wafer made of silicon or the like.

[0048] Then, with the suction source 16 in operation, the valve 14 is switched from the closed state to the open state. As a result, the lower surface of the holding table 18 is sucked through the communication passage 12a of the drive shaft 12, and the through hole 10e, the communication passages 10d and 10c, and the groove 10b of the table base 10, with leakage through the porous plate 22 being suppressed.

[0049] As a result, the gap between the lower surface of the holding table 18 and the upper surface of the table base 10 narrows over time, and the two surfaces come into close contact with each other. For example, by maintaining this state for 30 minutes to 3 hours, the two surfaces can be brought into sufficient contact with each other.

[0050] Next, when the lower surface of the holding table 18 and the upper surface of the table base 10 are sufficiently in close contact with each other, the holding table 18 is fixed to the table base 10 while the lower surface of the holding table 18 is kept under suction (fixing step: S4) (see FIG. 8).

[0051] Specifically, the bolt 56 is rotated with a predetermined torque in a direction in which the bolt 56 screws into the screw hole 10a of the table base 10. For example, the force (torque) for rotating the bolt 56 in the fixing step is 4 Nm.

[0052] Next, the upper surface (front surface) of the holding table 18 is ground (grinding step: S5) (see FIG. 9). Specifically, first, the valve 14 is switched from an open state to a closed state, and then the operation of the suction source 16 is stopped. Next, the sealing object 11 is removed from the upper surface of the holding table 18.

[0053] Next, the X-axis direction moving mechanism arranged inside the opening 4a of the base 4 is operated so that the center of the upper surface of the holding table 18 overlaps with the rotational trajectory of the multiple grinding stones 54 when the grinding wheel 50 is rotated.

[0054] Next, a rotation unit connected to the lower part of the drive shaft 12 rotates the holding table 18 together with the table base 10 via the drive shaft 12, and a motor 46 rotates the grinding wheel 50 via the spindle 44.

[0055] Next, the Z-axis direction moving mechanism 28 is operated so that the lower surfaces of the multiple grinding wheels 54 come into contact with the upper surface of the holding table 18. As a result, the upper surface side (front surface side) of the holding table 18 is ground and shaped into a shape corresponding to the side surface of a cone.

[0056] In the method for shaping the holding table shown in FIG. 4, prior to grinding (self-grinding) the upper surface side of the holding table 18, first, the holding table 18 is temporarily fixed to the table base 10 (temporary fixing step (S2)).

[0057] Then, with the upper surface of the holding table 18 sealed with the sealing material 11, the suction source 16 is operated to suck the lower surface (rear surface) of the holding table 18 and bring the lower surface of the holding table 18 into close contact with the upper surface (support surface) of the table base 10 (close contact step (S3)), and then the holding table 18 is fixed to the table base 10 (fixing step (S4)).

[0058] In this case, the gap between the lower surface of the holding table 18 and the upper surface of the table base 10 during self-grinding of the holding table 18 is narrower than when only the fixing step (S4) is performed without performing the temporary fixing step (S2) and the adhesion step (S3).

[0059] This allows the state of the holding table 18 during self-grinding to be closer to the state of the holding table 18 during grinding of the workpiece. As a result, when the holding table 18 is ground by this method, it becomes easier to grind the workpiece to a desired flatness.

[0060] The above is one aspect of the present invention, and the present invention is not limited to the above. For example, if a cooling water flow path for cooling the workpiece during grinding is formed inside the holding table 18, the above grinding step (S5) may be performed while running cooling water through this flow path. In this case, the state of the holding table 18 during self-grinding can be made even closer to the state of the holding table 18 during grinding of the workpiece.

[0061] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0062] 2: Grinding equipment 4: Base (4a: opening) 6: Table cover 8: Dust-proof and water-resistant cover 10: Table base (10a: screw hole, 10b: groove) (10c, 10d: communication path, 10e: through hole) 12: Drive shaft (12a: Communication passage) 14: Valve 16: Suction source 18: Holding table 20: Frame (20a: bottom wall, 20b: through hole, 20c: side wall) (20d: second cylindrical space, 20e: through hole) 22: Porous plate 24: Operation panel 26:Support structure 28:Z-axis direction movement mechanism 30: Z-axis guide rail 32: Z-axis moving plate 34: Screw shaft 36: Motor 38: Support 40: Grinding unit 42: Spindle housing 44: Spindle 46: Motor 48: Wheel mount 50: Grinding wheel 52: Wheel base 54: Grinding wheel 56: Bolt

Claims

[Claim 1] a grinding device including a table base having a support surface on which a back surface of a holding table having a surface on which a workpiece is placed is placed, a drive shaft fixed to the surface side of the table base opposite the support surface, a rotation unit which rotates the table base via the drive shaft, a suction source capable of sucking the workpiece placed on the surface of the holding table toward the holding table and of sucking the holding table placed on the support surface of the table base toward the table base, and a spindle to the tip of which can be attached a grinding wheel having a plurality of grinding stones arranged discretely in an annular shape, the method comprising: grinding the front surface side of the holding table to shape the front surface of the holding table, the method comprising: a placing step of placing the back surface of the holding table on the placement surface of the table base; a temporary fixing step of temporarily fixing the holding table to the table base with a fixing force smaller than a predetermined fixing force required for fixing the holding table to the table base using a fixing tool for fixing the holding table after the placing step; a contact step of, after the temporary fixing step, operating the suction source in a state in which the front surface of the holding table is sealed with a sealing material, thereby sucking the rear surface of the holding table and bringing the rear surface of the holding table and the mounting surface of the table base into close contact with each other; a fixing step of fixing the holding table to the table base with the predetermined fixing force using the fixing tool while keeping the back surface of the holding table sucked after the contact step; a grinding step of grinding the surface side of the holding table by rotating the table base via the drive shaft and contacting the plurality of grinding wheels with the surface of the holding table while rotating the grinding wheel via the spindle in a state in which the sealing material is removed from the surface of the holding table after the fixing step; A method for shaping a holding table, comprising:

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