Chuck table, grinding device, and grinding method for workpiece

Abstract

To prevent a specific workpiece from being ground twice when performing creep feed grinding in the state that a workpiece is held on each of a plurality of holding surfaces of a chuck table.SOLUTION: A plurality of holding surfaces for a chuck table are provided so that their heights from a reference level are in ascending order along a first direction parallel to the surfaces. Therefore, when the chuck table is used, creep feed grinding of a workpiece held on each of the plurality of holding surfaces can be performed in the state that a grinding unit is positioned at a different height. In this case, the workpiece for which creep feed grinding is performed is positioned at a lower position seen from the grinding unit when other workpieces are ground. Thus, in the creep feed grinding, it is possible to prevent a specific workpiece from being ground twice.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a chuck table that holds a workpiece on each of a plurality of holding surfaces, a grinding device that includes this chuck table, and a grinding method for grinding a workpiece using this grinding device. [Background technology]

[0002] Device chips such as IC (Integrated Circuit) and LSI (Large Scale Integration) are essential components in various electronic devices such as mobile phones, personal computers, etc. Such chips are manufactured, for example, by dividing a wafer on which a large number of devices are formed into regions each containing an individual device.

[0003] Furthermore, the wafer is often thinned before being divided in order to reduce the size and weight of the chips. One method for thinning the wafer is grinding using a grinding device. The grinding device includes, for example, a chuck table having a holding surface for holding the wafer, and a grinding unit provided above the chuck table and having a detachable spindle at the bottom end thereof, the grinding wheel having a plurality of grinding stones arranged in a circular pattern.

[0004] In such a grinding device, the wafer may be thinned by a grinding method also called creep feed grinding (see, for example, Patent Document 1). In this grinding method, the front side of the wafer is first held on the holding surface of the chuck table. Next, with the grinding unit positioned behind the chuck table, the lower surface of each of the multiple grinding wheels is positioned at a height between the rear surface (upper surface) and the front surface (lower surface) of the wafer.

[0005] Then, while the chuck table and the grinding unit are moved relative to each other in the front-rear direction, multiple grinding wheels located in front of the rotating grinding wheel are brought into contact with the upper surface (back surface) of the wafer held on the chuck table from its rear side. This causes the multiple grinding wheels to grind the upper surface (back surface) of the wafer from its rear end to its front end. As a result, the wafer is thinned to a specified finishing thickness. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-28550 A Summary of the Invention [Problem to be solved by the invention]

[0007] Grinding machines are used not only to thin disk-shaped wafers, but also to thin workpieces such as rectangular parallelepiped package substrates, such as CSP (Chip Size Package) substrates and QFN (Quad Flat Non-leaded package) substrates. Grinding machines used to grind such workpieces generally include a chuck table having a plurality of holding surfaces, each of which has the same shape (e.g., rectangular) and is parallel to one another and arranged in the front-rear direction.

[0008] When creep feed grinding is performed while the workpieces are held by each of the multiple holding surfaces, the workpieces are ground in order from the rear end, resulting in each of the multiple workpieces being thinned to a predetermined finishing thickness.

[0009] However, when multiple workpieces are thinned in this manner, only the workpiece located at the rear end of the multiple workpieces may be ground twice. Specifically, the workpiece may be first ground by multiple grinding wheels located in front of the rotating grinding wheel, and then ground again by multiple grinding wheels located behind the rotating grinding wheel.

[0010] In this case, there is a risk that the thickness of the multiple workpieces after grinding will vary, and there is also a risk that unintended saw marks will be formed on the top surface of the workpiece located at the rear end of the multiple workpieces, causing scratches or cracks on the workpiece.

[0011] In view of this, an object of the present invention is to prevent a particular workpiece from being ground twice when creep feed grinding is performed with the workpiece held on each of the multiple holding surfaces of the chuck table. [Means for solving the problem]

[0012] According to one aspect of the present invention, there is provided a chuck table including a first holding surface and a second holding surface, each of which has the same shape and is parallel to each other, and a reference surface surrounding each of the first holding surface and the second holding surface in a plan view and parallel to the first holding surface and the second holding surface, the first holding surface and the second holding surface being arranged such that their heights from the reference surface increase in an ascending order along a first direction parallel to each of the first holding surface and the second holding surface, the first holding surface and the second holding surface being arranged such that their heights from the reference surface increase in an ascending order along a first direction parallel to each of the first holding surface and the second holding surface being arranged such that their heights from the reference surface increase in an ascending order along a first direction parallel to each of the first holding surface and the second holding surface being arranged such that their heights from the reference surface increase in an ascending order along a first direction parallel to each of the first holding surface and the second holding surface are ... When viewed from a direction perpendicular to the first direction and parallel to the reference plane A chuck table is provided with a gap between the first holding surface and the second holding surface in each side view.

[0013] According to another aspect of the present invention, there is provided a grinding apparatus comprising: the above-mentioned chuck table; a grinding unit having a spindle having a grinding wheel with a plurality of grinding stones arranged in a ring attached to its tip; a first moving mechanism that moves the chuck table and the grinding unit relatively along the first direction; and a second moving mechanism that moves the chuck table and the grinding unit relatively along a second direction perpendicular to each of the reference surface and the first holding surface and the second holding surface.

[0014] According to yet another aspect of the present invention, the grinding unit includes a chuck table which holds a workpiece on each of the first and second holding surfaces, the first and second holding surfaces being arranged in ascending order of height from the reference surface along a first direction parallel to the first and second holding surfaces, the first and second holding surfaces being arranged in ascending order of height from the reference surface along a first direction parallel to the first and second holding surfaces, a grinding unit having a spindle at the tip of which is attached a grinding wheel having a plurality of grinding stones arranged in an annular shape, a first moving mechanism which moves the chuck table and the grinding unit relatively along the first direction, and a second moving mechanism which moves the chuck table and the grinding unit relatively along a second direction perpendicular to the reference surface and each of the first and second holding surfaces. Provided is a grinding method for a workpiece, which uses a grinding device to grind the workpiece, comprising: a holding step of holding the workpiece on each of the first holding surface and the second holding surface; and a grinding step of, after the holding step, moving the chuck table and the grinding unit relatively along the first direction, and bringing the rotating multiple grinding wheels into contact with the workpiece held on each of the first holding surface and the second holding surface, while gradually widening the gap between the reference surface and the multiple grinding wheels along the second direction so that the workpiece held on each of the first holding surface and the second holding surface has a predetermined finishing thickness, thereby grinding the workpiece.

[0015] According to another aspect of the present invention, there is provided a grinding apparatus including a chuck table including a first holding surface and a second holding surface each having the same shape and parallel to each other, and a reference surface surrounding each of the first holding surface and the second holding surface in a plan view and parallel to the first holding surface and the second holding surface, and holding a workpiece on each of the first holding surface and the second holding surface; and a spindle having a chuck table grinding wheel on which a plurality of chuck table grinding wheels are arranged in a ring or a workpiece grinding wheel on which a plurality of workpiece grinding wheels are arranged in a ring, attached to a tip end thereof. a first moving mechanism for relatively moving the chuck table and the grinding unit along a first direction parallel to the reference surface, the first holding surface, and the second holding surface, and a second moving mechanism for relatively moving the chuck table and the grinding unit along a second direction perpendicular to the reference surface, the first holding surface, and the second holding surface, a holding surface grinding step of grinding the chuck table by bringing the rotating grinding wheels for the chuck table into contact with the chuck table while moving the chuck table relatively along the first direction and gradually increasing a distance along the second direction between the reference surface and the plurality of grinding wheels for the chuck table so that the heights of the first holding surface and the second holding surface from the reference surface are in ascending order along the first direction; a holding step of holding the workpiece on each of the first holding surface and the second holding surface after the holding step; and a grinding step of relatively moving the grinding unit, which has a workpiece grinding wheel attached to the tip of the spindle, along the first direction, and bringing the rotating grinding wheels for the workpiece into contact with the workpiece held on each of the first holding surface and the second holding surface while gradually increasing the distance along the second direction between the reference surface and the multiple grinding wheels for the workpiece so that the workpiece held on each of the first holding surface and the second holding surface has a predetermined finishing thickness, thereby grinding the workpiece. Effect of the Invention

[0016] In the chuck table of the present invention, the first and second holding surfaces are provided in ascending order of height from a reference surface along a first direction parallel to each other, and therefore, when using this chuck table, creep feed grinding can be performed on workpieces held on the first and second holding surfaces with the grinding units positioned at different heights.

[0017] In this case, the workpiece on which creep feed grinding has been performed is positioned below the grinding unit when other workpieces are ground, thereby preventing a particular workpiece from being ground twice in creep feed grinding. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1(A) is a top view that illustrates an example of a chuck table, and FIG. 1(B) is a side view that illustrates an example of the chuck table. [Diagram 2] FIG. 2 is a partial cross-sectional side view that illustrates a schematic diagram of an example of a grinding apparatus that includes the chuck table shown in FIG. 1(A) and FIG. 1(B). [Diagram 3] FIG. 3 is a flow chart that illustrates a schematic example of a method for grinding a workpiece using the grinding apparatus illustrated in FIG. [Figure 4] FIG. 4(A) is a side view that typically shows the state of the holding step, and FIG. 4(B) and FIG. 4(C) are side views that typically show the state of the grinding step. [Diagram 5] 5(A), 5(B) and 5(C) are side views that typically show the state of the grinding step. [Figure 6] 6(A), 6(B) and 6(C) are side views that diagrammatically show the state of the grinding step. [Figure 7] FIG. 7 is a flow chart that illustrates a modified example of the method for grinding a workpiece. [Figure 8]8(A), 8(B) and 8(C) are side views that typically show the state of the support surface grinding step. [Figure 9] 9(A), 9(B) and 9(C) are side views that typically show the state of the support surface grinding step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1(A) is a top view showing an example of a chuck table, and Fig. 1(B) is a side view showing an example of the chuck table. The chuck table 2 shown in Fig. 1(A) and Fig. 1(B) has a disk-shaped base portion 4 made of, for example, ceramics.

[0020] The base portion 4 has a flat upper surface (reference surface) 4a. The reference surface 4a is provided with a plurality of (for example, four) rectangular parallelepiped holders 6, 8, 10, and 12 arranged along a first direction (D1) parallel to the reference surface 4a and protruding along a second direction (D2) perpendicular to the reference surface 4a.

[0021] Each of the multiple holding parts 6, 8, 10, 12 has a rectangular parallelepiped frame 6a, 8a, 10a, 12a made of ceramics or the like, and a recess is formed in the upper part of each of the frames 6a, 8a, 10a, 12a. A rectangular parallelepiped porous plate 6b, 8b, 10b, 12b made of ceramics or the like is fixed in this recess.

[0022] Furthermore, the porous plates 6b, 8b, 10b, and 12b have upper surfaces parallel to the reference plane 4a. Furthermore, inside the base part 4 and the multiple holding parts 6, 8, 10, and 12, respectively, suction paths are provided to connect the lower surfaces of the porous plates 6b, 8b, 10b, and 12b to a suction source such as an ejector.

[0023] When the suction source is operated with the suction passage connected to it, negative pressure is generated in the space near the upper surfaces of the porous plates 6b, 8b, 10b, and 12b, and therefore the upper surfaces 6c, 8c, 10c, and 12c of the multiple holders 6, 8, 10, and 12 function as holding surfaces for holding the workpiece.

[0024] The reference surface 4a of the base portion 4 is provided so as to surround the upper surfaces (holding surfaces) 6c, 8c, 10c, and 12c of the holders 6, 8, 10, and 12 in a plan view. Each of the holding surfaces 6c, 8c, 10c, and 12c is parallel to the reference surface 4a.

[0025] The holding surfaces 6c, 8c, 10c, and 12c have the same shape. Specifically, each of the holding surfaces 6c, 8c, 10c, and 12c has a rectangular shape having a pair of short sides extending along the first direction and a pair of long sides extending along a third direction (D3) perpendicular to the first and second directions.

[0026] However, the heights of the multiple holding surfaces 6c, 8c, 10c, and 12c from the reference plane 4a are different. Specifically, the heights of the multiple holding surfaces 6c, 8c, 10c, and 12c from the reference plane 4a are in ascending order along the first direction. That is, the holding surface 6c is lower than the other holding surfaces 8c, 10c, and 12c. Furthermore, the holding surface 8c is lower than the holding surfaces 10c and 12c. Furthermore, the holding surface 10c is lower than the holding surface 12c.

[0027] The height difference between a pair of adjacent holding surfaces (e.g., holding surface 6c and holding surface 8c) along the first direction is determined in consideration of the variation in thickness of the workpiece held by each of the multiple holding surfaces 6c, 8c, 10c, and 12c. Specifically, this difference is 10 μm or more and 300 μm or less (e.g., 50 μm).

[0028] Fig. 2 is a partial cross-sectional side view showing a schematic diagram of an example of a grinding device including a chuck table 2. 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 the X-axis and Y-axis directions.

[0029] The grinding device 14 shown in Fig. 2 includes a base 16 that supports or houses each of the components. A rectangular parallelepiped opening 16a is provided on the upper surface side of the base 16. An X-axis moving mechanism (first moving mechanism) 18 is provided inside the opening 16a. This X-axis moving mechanism 18 has a screw shaft 20 that extends along the X-axis direction.

[0030] A motor 22 for rotating the screw shaft 20 is connected to one end of the screw shaft 20. In addition, a nut portion 24 for accommodating balls that roll on the surface of the rotating screw shaft 20 is provided on the surface of the screw shaft 20 on which a spiral groove is formed, thereby forming a ball screw.

[0031] That is, when the screw shaft 20 rotates, the balls circulate inside the nut portion 24, and the nut portion 24 moves along the X-axis direction. The lower portion of the chuck table 2 is attached to the upper portion of the nut portion 24 so that the first direction (D1), second direction (D2), and third direction (D3) are parallel to the X-axis direction, Y-axis direction, and Z-axis direction, respectively. Therefore, when the screw shaft 20 is rotated by the motor 22, the chuck table 2 moves along the X-axis direction together with the nut portion 24.

[0032] Furthermore, the grinding device 14 has a built-in suction source (not shown), which is connected to suction paths provided inside the base 4 and each of the multiple holding parts 6, 8, 10, and 12 via a valve (not shown) or the like. Therefore, by opening the valve while the suction source is in operation, the workpiece can be held on the holding surfaces 6c, 8c, 10c, and 12c of the multiple holding parts 6, 8, 10, and 12.

[0033] A rectangular parallelepiped support structure 26 is provided behind the chuck table 2 and the X-axis moving mechanism 18 (on the right side of the paper in FIG. 2). A Z-axis moving mechanism (second moving mechanism) 28 is provided on the surface (front surface) side of the support structure 26. This Z-axis moving mechanism 28 is connected to a grinding unit 40 (described later) and moves the grinding unit 40 along the Z-axis direction.

[0034] The Z-axis movement mechanism 28 has a pair of guide rails 30 that are fixed to the front surface side of the support structure 26 and extend along the Z-axis direction. A moving plate 32 is connected to the front sides of the pair of guide rails 30 in a manner that allows it to slide along the pair of guide rails 30.

[0035] A screw shaft 34 extending along the Z-axis direction is disposed between the pair of guide rails 30. A motor 36 for rotating the screw shaft 34 is connected to one end of the screw shaft 34. In addition, a nut portion 38 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.

[0036] That is, when the screw shaft 34 rotates, the balls circulate inside the nut portion 38, and the nut portion 38 moves along the Z-axis direction. The nut portion 38 is fixed to the back surface (rear surface) side of the moving plate 32. Therefore, when the screw shaft 34 is rotated by the motor 36, the moving plate 32 moves along the Z-axis direction together with the nut portion 38.

[0037] A grinding unit 40 is provided on the surface (front) side of the movable plate 32. The grinding unit 40 has a hollow, cylindrical support member 42 fixed to the surface side of the movable plate 32. A hollow, cylindrical housing 44 is accommodated in the support member 42. The housing 44 is fixed to the bottom wall of the support member 42 via a connecting member 46 provided on the lower surface thereof.

[0038] A cylindrical spindle 48 extending along the Z-axis direction is rotatably housed in the housing 44. The tip (lower end) of the spindle 48 is exposed from the housing 44 and protrudes downward from the bottom surface of the support member 42 through an opening provided in the bottom wall of the support member 42. In addition, a disk-shaped mount 50 made of metal or the like is fixed to the tip of the spindle 48.

[0039] The diameter of this mount 50 is shorter than the diameter of the chuck table 2 (the diameter of the reference surface 4a of the base portion 4). Fig. 2 shows the mount 50 having a diameter approximately half the diameter of the chuck table 2. In addition, an annular grinding wheel 52 is attached to the underside of the mount 50 in a removable manner.

[0040] The grinding wheel 52 has an annular wheel base 54 made of a metal such as aluminum or stainless steel, and the outer diameter of the wheel base 54 is approximately equal to the diameter of the mount 50. That is, in FIG. 2, the wheel base 54 has a diameter approximately half that of the chuck table 2.

[0041] The upper surface of the wheel base 54 is fixed to the lower surface of the mount 50 by fasteners such as bolts. A plurality of grinding wheels 56 are fixed to the lower surface of the wheel base 54 and are arranged in a circular pattern. Each of the grinding wheels 56 has, for example, a rectangular parallelepiped shape, and is arranged at approximately equal intervals along the circumferential direction of the wheel base 54.

[0042] The grinding wheel 56 is formed by fixing abrasive grains made of diamond or cBN (cubic boron nitride) with a bonding material (bond material) made of metal bond, resin bond, vitrified bond, etc. However, there are no limitations on the material, shape, structure, size, etc. of the grinding wheel 56. In addition, the number of multiple grinding wheels 56 can be set arbitrarily.

[0043] A rotary drive source (not shown) such as a motor for rotating the spindle 48 is connected to the base end (upper end) of the spindle 48. When this rotary drive source rotates the spindle 48 about a rotation axis along the Z-axis direction, the mount 50 and the grinding wheel 52 (wheel base 54 and multiple grinding stones 56) rotate together with the spindle 48.

[0044] Fig. 3 is a flow chart showing a schematic example of a method for grinding a workpiece using the grinding device 14. In this method, first, the workpiece is held on each of the multiple holding surfaces 6c, 8c, 10c, and 12c of the chuck table 2 (holding step: S1). Fig. 4(A) is a side view showing a schematic view of the holding step (S1).

[0045] In this holding step (S1), first, the X-axis moving mechanism 18 is operated to position the workpiece 11 at a position (e.g., a position separated from the grinding unit 40) where it can be loaded onto the multiple holding surfaces 6c, 8c, 10c, and 12c of the chuck table 2. Next, the multiple workpieces 11 are loaded onto each of the multiple holding surfaces 6c, 8c, 10c, and 12c of the chuck table 2.

[0046] The workpiece 11 is, for example, a rectangular parallelepiped package substrate such as a CSP substrate or a QFN substrate, and the shapes of its upper and lower surfaces are substantially the same as the shapes of the plurality of holding surfaces 6c, 8c, 10c, and 12c. Next, while a suction source that communicates with a suction path provided inside the chuck table 2 via a valve or the like is in operation, the valve is opened. This completes the holding step (S1).

[0047] In the grinding method of the workpiece shown in FIG. 3, after a holding step (S1), creep feed grinding is performed on the workpiece 11 held on each of the multiple holding surfaces 6c, 8c, 10c, 12c with the grinding unit 40 positioned at different heights (grinding step: S2).

[0048] Specifically, in the grinding step (S2), the chuck table 2 is moved along the X-axis direction (first direction) while the distance between the reference surface 4a and the multiple grinding wheels 56 along the Z-axis direction (second direction) is gradually increased so that the workpiece 11 held on each of the multiple holding surfaces 6c, 8c, 10c, 12c has a predetermined finishing thickness, and the rotating multiple grinding wheels 56 are brought into contact with the workpiece 11 held on each of the multiple holding surfaces 6c, 8c, 10c, 12c to grind the workpiece 11.

[0049] 4(B), 4(C), 5(A), 5(B), 5(C), 6(A), 6(B) and 6(C) are side views showing the grinding step (S2) in a schematic manner. In the grinding step (S2), the Z-axis moving mechanism 28 first lowers the grinding unit 40 so that the lower surfaces of the grinding stones 56 of the grinding wheel 52 are positioned higher than the holding surface 6c by the finishing thickness of the workpiece 11 (see FIG. 4(B)).

[0050] Next, while moving the chuck table 2 backward along the X-axis direction, the grinding stones 56 located in front of the rotating grinding wheel 52 are brought into contact with the upper surface of the workpiece 11 held on the holding surface 6c. As a result, the upper surface of the workpiece 11 held on the holding surface 6c is ground from the rear end to the front end, and the workpiece 11 is thinned to a predetermined finishing thickness (see FIG. 4(C)).

[0051] Next, the Z-axis movement mechanism 28 raises the grinding unit 40 so that the lower surfaces of the multiple grinding stones 56 of the grinding wheel 52 are positioned higher than the holding surface 8c by the finishing thickness of the workpiece 11 (see FIG. 5(A)).

[0052] Next, while the chuck table 2 is moved backward along the X-axis direction, the grinding stones 56 located in front of the rotating grinding wheel 52 are brought into contact with the upper surface of the workpiece 11 held on the holding surface 8c. As a result, the upper surface of the workpiece 11 held on the holding surface 8c is ground from the rear end to the front end, and the workpiece 11 is thinned to a predetermined finishing thickness (see FIG. 5(B)).

[0053] At this time, the multiple grinding wheels 56 located on the rear side of the rotating grinding wheel 52 are located above the workpiece 11 held on the holding surface 6c and do not come into contact with the workpiece 11. In other words, the workpiece 11 held on the holding surface 6c is not ground again by the multiple grinding wheels 56.

[0054] Next, the Z-axis movement mechanism 28 raises the grinding unit 40 so that the lower surfaces of the multiple grinding stones 56 of the grinding wheel 52 are positioned higher than the holding surface 10c by the finishing thickness of the workpiece 11 (see FIG. 5(C)).

[0055] Next, while moving the chuck table 2 backward along the X-axis direction, the grinding stones 56 located in front of the rotating grinding wheel 52 are brought into contact with the upper surface of the workpiece 11 held on the holding surface 10c. As a result, the upper surface of the workpiece 11 held on the holding surface 10c is ground from the rear end to the front end, and the workpiece 11 is thinned to a predetermined finishing thickness (see FIG. 6(A)).

[0056] At this time, the multiple grinding wheels 56 located on the rear side of the rotating grinding wheel 52 are located above the workpiece 11 held on the holding surface 8c and do not come into contact with the workpiece 11. In other words, the workpiece 11 held on the holding surface 8c is not ground again by the multiple grinding wheels 56.

[0057] Next, the Z-axis movement mechanism 28 raises the grinding unit 40 so that the lower surfaces of the multiple grinding stones 56 of the grinding wheel 52 are positioned higher than the holding surface 12c by the finishing thickness of the workpiece 11 (see FIG. 6(B)).

[0058] Next, while moving the chuck table 2 backward along the X-axis direction, the grinding stones 56 located in front of the rotating grinding wheel 52 are brought into contact with the upper surface of the workpiece 11 held on the holding surface 12c. As a result, the upper surface of the workpiece 11 held on the holding surface 12c is ground from the rear end to the front end, and the workpiece 11 is thinned to a predetermined finishing thickness (see FIG. 6(C)).

[0059] At this time, the multiple grinding wheels 56 located on the rear side of the rotating grinding wheel 52 are located above the workpiece 11 held on the holding surface 10c and do not come into contact with the workpiece 11. In other words, the workpiece 11 held on the holding surface 10c is not ground again by the multiple grinding wheels 56. This completes the grinding step (S2).

[0060] In the chuck table 2, a plurality of holding surfaces 6c, 8c, 10c, and 12c are provided in ascending order of height from the reference surface 4a along a first direction parallel to each of the holding surfaces 6c, 8c, 10c, and 12c. Therefore, when using this chuck table 2, creep feed grinding can be performed on the workpiece 11 held on each of the plurality of holding surfaces 6c, 8c, 10c, and 12c with the grinding unit 40 positioned at different heights.

[0061] In this case, the workpiece 11 on which creep feed grinding has been performed (for example, the workpiece 11 held on the holding surface 6c) is positioned below the grinding unit 40 when another workpiece 11 (for example, the workpiece 11 held on the holding surface 8c) is ground. This makes it possible to prevent a particular workpiece 11 from being ground twice in this creep feed grinding.

[0062] Furthermore, in the grinding method for the workpiece of the present invention, prior to the holding step (S1), the chuck table 2 may be machined in the grinding device 14 so that the heights of the multiple holding surfaces of the chuck table 2 from the reference plane 4a are in ascending order along the first direction. This makes it possible to carry out the grinding step (S2) even in a case where, for example, the heights of the upper surfaces of the holding parts 6, 8, 10 from the reference plane 4a are equal to the height of the upper surface (holding surface) 12c of the holding part 12 from the reference plane 4a.

[0063] In addition, when grinding the chuck table 2, a grinding wheel (grinding wheel for the chuck table) of a different type is generally used from the grinding wheel (grinding wheel for the workpiece) used when grinding the workpiece 11. In other words, the chuck table 2 is generally ground using a grinding wheel for the chuck table in which a plurality of grinding wheels (grinding wheels for the chuck table) of a different type from the plurality of grinding wheels (grinding wheels for the workpiece) included in the grinding wheel for the workpiece are arranged discretely in a ring shape.

[0064] 7 is a flow chart showing an example of a grinding method for a workpiece, prior to the holding step (S1), for machining the chuck table 2. In this method, first, the chuck table 2 is ground so that the heights of the multiple holding surfaces of the chuck table 2 are in ascending order along the X-axis direction (first direction) (holding surface grinding step: S3).

[0065] Specifically, in the holding surface grinding step (S3), the chuck table 2 is moved along the X-axis direction (first direction) and the spacing between the reference surface 4a and the multiple chuck table grinding wheels along the Z-axis direction (second direction) is gradually increased so that the heights of the multiple holding surfaces from the reference surface 4a ascend along the X-axis direction, while the multiple rotating chuck table grinding wheels are brought into contact with the chuck table 2 to grind the chuck table 2.

[0066] 8(A), 8(B), 8(C), 9(A), 9(B) and 9(C) are side views showing the holding surface grinding step (S3) in a schematic manner. In the holding surface grinding step (S3), the Z-axis moving mechanism 28 first lowers the grinding unit 40 so that the lower surfaces of the multiple chuck table grinding stones 56a, which are arranged in a circular and discrete manner on the lower surface side of the wheel base 54a of the chuck table grinding wheel 52a, are positioned lower than the holding surface 12c and higher than the reference surface 4a (see FIG. 8(A)).

[0067] Next, while moving the chuck table 2 backward along the X-axis direction, a plurality of chuck table grinding stones 56a located in front of the rotating chuck table grinding wheel 52a are brought into contact with the upper surface side of the holding portion 6. As a result, the upper surface side of the holding portion 6 is ground from the rear end to the front end, and the upper surface of the holding portion 6 moves to a position lower than the holding surface 12c, i.e., the holding surface 6c is formed (see FIG. 8(B)).

[0068] Next, the Z-axis movement mechanism 28 raises the grinding unit 40 so that the lower surfaces of the multiple chuck table grinding wheels 56a are positioned lower than the holding surface 12c and higher than the holding surface 6c (see FIG. 8(C)).

[0069] Next, while moving the chuck table 2 backward along the X-axis direction, a plurality of chuck table grinding stones 56a located in front of the rotating chuck table grinding wheel 52a are brought into contact with the upper surface side of the holding portion 8. As a result, the upper surface side of the holding portion 8 is ground from the rear end to the front end, and the upper surface of the holding portion 8 moves to a position lower than the holding surface 12c and higher than the holding surface 6c, i.e., the holding surface 8c is formed (see FIG. 9(A)).

[0070] Next, the Z-axis movement mechanism 28 raises the grinding unit 40 so that the lower surfaces of the multiple chuck table grinding wheels 56a are positioned lower than the holding surface 12c and higher than the holding surface 8c (see FIG. 9(B)).

[0071] Next, while moving the chuck table 2 backward along the X-axis direction, a plurality of chuck table grinding stones 56a located in front of the rotating chuck table grinding wheel 52a are brought into contact with the upper surface side of the holding portion 10. As a result, the upper surface side of the holding portion 10 is ground from the rear end to the front end, and the upper surface of the holding portion 10 moves to a position lower than the holding surface 12c and higher than the holding surface 8c, i.e., the holding surface 10c is formed (see FIG. 9(C)).

[0072] Thus, the holding surface grinding step (S3) is completed. In the grinding method of the workpiece shown in Fig. 7, after the holding surface grinding step (S3), the above-mentioned holding step (S1) and grinding step (S2) are performed in this order. As a result, in the grinding method of the workpiece shown in Fig. 7, it is possible to prevent a specific workpiece 11 from being ground twice, as in the grinding method of the workpiece shown in Fig. 3.

[0073] The above-mentioned content is one aspect of the present invention, and the content of the present invention is not limited to the above-mentioned content. For example, in the chuck table of the present invention, the shape of the multiple holding surfaces is not limited to a rectangle, and may be a polygon having three or five or more corners, a circle, or an ellipse.

[0074] In the chuck table of the present invention, the base portion 4 may be in the shape of a rectangular parallelepiped or an elliptical plate. In the chuck table of the present invention, some of the holding surfaces included in the plurality of holding surfaces may have the same height from the reference plane 4a.

[0075] Specifically, when the diameter of the grinding wheel 52 is relatively long (for example, when the diameter of the grinding wheel 52 is 70% or more and 90% or less of the diameter of the chuck table 2), when the workpiece 11 held on the upper surface (holding surface) of the holding portion 8 and / or the holding portion 10 is ground with the multiple grinding wheels 56 located in front of the grinding wheel 52, the multiple grinding wheels 56 located behind it may not reach above the holding portion 6.

[0076] In such a case, for example, the heights of the upper surfaces (holding surfaces) of the holding portions 6 and 8 from the reference plane 4a may be the same. Alternatively, the heights of the upper surfaces (holding surfaces) of the holding portions 6, 8, and 10 from the reference plane 4a may be the same. That is, in the chuck table of the present invention, the multiple holding surfaces may be classified into low holding surfaces (for example, the upper surfaces of the holding portions 6 and 8 or the upper surfaces of the holding portions 6, 8, and 10) that are equal in height to each other, and holding surfaces that are higher than the low holding surfaces (for example, the upper surfaces of the holding portions 10 and 12 or the upper surface of the holding portion 12).

[0077] In addition, in the grinding device of the present invention, the X-axis moving mechanism 18 may be replaced with an X-axis moving mechanism that moves the grinding unit 40 along the X-axis direction. That is, in the grinding device of the present invention, it is only necessary that the chuck table 2 and the grinding unit 40 can move relatively along the X-axis direction, and the components therefor are not limited.

[0078] Similarly, in the grinding device of the present invention, the Z-axis movement mechanism 28 may be replaced with a Z-axis movement mechanism that moves the chuck table 2 along the Z-axis direction. That is, in the grinding device of the present invention, it is only necessary that the chuck table 2 and the grinding unit 40 can move relatively along the Z-axis direction, and the components therefor are not limited.

[0079] In addition, in the grinding method of the workpiece of the present invention, the grinding wheel for the chuck table and the grinding wheel for the workpiece may be the same grinding wheel. In other words, in the grinding method of the workpiece of the present invention, the chuck table 2 and the workpiece 11 may be ground using a plurality of the same grinding wheels.

[0080] 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]

[0081] 2: Chuck table 4: Base part (4a: Top surface (reference surface)) 6: Holding part (6a: frame body, 6b: porous plate, 6c: top surface (holding surface)) 8: Holding part (8a: frame body, 8b: porous plate, 8c: top surface (holding surface)) 10: Holding part (10a: frame body, 10b: porous plate, 10c: top surface (holding surface)) 12: Holding part (12a: frame body, 12b: porous plate, 12c: top surface (holding surface)) 14: Grinding equipment 16: Base (16a: opening) 18:X-axis movement mechanism (first movement mechanism) 20: Screw shaft 22: Motor 24: Nut part 26:Support structure 28:Z-axis movement mechanism (second movement mechanism) 30: Guide rail 32: Moving plate 34: Screw shaft 36: Motor 38: Nut part 40: Grinding unit 42: Support member 44: Housing 46: Connection parts 48: Spindle 50: Mount 52: Grinding wheel (52a: Grinding wheel for chuck table) 54(54a): Wheel base 56: Grinding wheel (56a: Grinding wheel for chuck table)

Claims

1. A chuck table including a first holding surface and a second holding surface, each of which has the same shape and is parallel to each other, and a reference surface surrounding each of the first holding surface and the second holding surface in a plan view and being parallel to the first holding surface and the second holding surface, the chuck table holding a workpiece on each of the first holding surface and the second holding surface, the first holding surface and the second holding surface are provided in ascending order of height from the reference surface along a first direction parallel to each of the first holding surface and the second holding surface, A chuck table characterized in that a gap exists between the first holding surface and the second holding surface when viewed in a plan view and when viewed from a side view when viewed from a direction perpendicular to the first direction and parallel to the reference plane.

2. The chuck table according to claim 1 ; a grinding unit having a spindle on the tip of which a grinding wheel having a plurality of grinding stones arranged in a circular manner is attached; a first moving mechanism that relatively moves the chuck table and the grinding unit along the first direction; a second moving mechanism that relatively moves the chuck table and the grinding unit along a second direction perpendicular to the reference surface, the first holding surface, and the second holding surface.

3. a chuck table including a first holding surface and a second holding surface each having the same shape and parallel to each other, and a reference surface surrounding each of the first holding surface and the second holding surface in a plan view and parallel to the first holding surface and the second holding surface, the heights from the reference surface being in ascending order along a first direction parallel to each of the first holding surface and the second holding surface, the chuck table holding a workpiece with each of the first holding surface and the second holding surface being arranged in ascending order of height from the reference surface along a first direction parallel to each of the first holding surface and the second holding surface; a grinding unit having a spindle on the tip of which a grinding wheel having a plurality of grinding stones arranged in a circular manner is attached; a first moving mechanism that relatively moves the chuck table and the grinding unit along the first direction; a second moving mechanism that relatively moves the chuck table and the grinding unit along a second direction perpendicular to the reference surface, the first holding surface, and the second holding surface; A method for grinding a workpiece using a grinding device comprising: a holding step of holding the workpiece on each of the first holding surface and the second holding surface; a grinding step of relatively moving the chuck table and the grinding unit along the first direction after the holding step, and bringing the rotating grinding wheels into contact with the workpiece held on each of the first holding surface and the second holding surface, while gradually widening the gap between the reference surface and the plurality of grinding wheels along the second direction so that the workpiece held on each of the first holding surface and the second holding surface has a predetermined finishing thickness, thereby grinding the workpiece; A method for grinding a workpiece, comprising:

4. a chuck table including a first holding surface and a second holding surface each having the same shape and parallel to each other, and a reference surface surrounding each of the first holding surface and the second holding surface in a plan view and parallel to the first holding surface and the second holding surface, the chuck table holding a workpiece on each of the first holding surface and the second holding surface; a grinding unit having a spindle on the tip of which is attached a grinding wheel for a chuck table having a plurality of grinding wheels for the chuck table arranged in a ring or a grinding wheel for a workpiece having a plurality of grinding wheels for a workpiece arranged in a ring; a first moving mechanism that relatively moves the chuck table and the grinding unit along a first direction parallel to each of the reference surface, the first holding surface, and the second holding surface; a second moving mechanism that relatively moves the chuck table and the grinding unit along a second direction perpendicular to the reference surface, the first holding surface, and the second holding surface, a holding surface grinding step of relatively moving the chuck table and the grinding unit having a grinding wheel for the chuck table attached to a tip of the spindle along the first direction, and grinding the chuck table by bringing the rotating grinding wheels for the chuck table into contact with the chuck table while gradually increasing the intervals along the second direction between the reference surface and the plurality of grinding wheels for the chuck table so that the heights of the first holding surface and the second holding surface from the reference surface are in ascending order along the first direction; a holding step of holding the workpiece on each of the first holding surface and the second holding surface after the holding surface grinding step; a grinding step in which, after the holding step, the chuck table and the grinding unit having the workpiece grinding wheel attached to the tip of the spindle are moved relatively along the first direction, and the rotating grinding wheels for the workpiece are brought into contact with the workpiece held on each of the first holding surface and the second holding surface while gradually increasing the distance between the reference surface and the plurality of grinding wheels for the workpiece along the second direction so that the workpiece held on each of the first holding surface and the second holding surface has a predetermined finishing thickness, thereby grinding the workpiece; A method for grinding a workpiece, comprising:

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