Grinding method of workpiece

Abstract

To provide a grinding method for workpiece capable of promoting the self-sharpening action of a plurality of grindstones without turning down the holding power of a binder for holding abrasive grains.SOLUTION: A grinding method for workpiece comprises grinding the ground face side of the workpiece after forming a toric groove on the ground face of the workpiece. In this grinding case, the ground face side of the workpiece is ground while an area near the ground face (underside) of respective side faces of a plurality of grindstones collides with the groove side formed on the ground face of the workpiece. Such a collision makes a binder of the ground face side of the workpiece easy to be ground. Accordingly, the self-sharpening action of the grindstones respectively can be promoted without turning down the holding power of the binder for holding abrasive grains.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for grinding a workpiece, which grinds the ground surface side of the workpiece so that the entire area of the disk-shaped workpiece becomes the finished thickness.

Background Art

[0002] Chips of devices such as IC (Integrated Circuit) and LSI (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 regions each including an individual device.

[0003] Furthermore, this workpiece is often thinned before being divided for the purpose of miniaturizing and lightening the chip. Thinning of the workpiece is performed, for example, by grinding the back surface side of the workpiece in a grinding apparatus. Such a grinding apparatus includes a chuck table having a holding surface (upper surface) shaped to correspond to the side surface of a cone and rotatable about a straight line passing through the center of this holding surface as a rotation axis.

[0004] Above this chuck table, a grinding unit having a spindle to which an annular grinding wheel can be attached at its tip is provided. The grinding wheel includes an annular wheel base and a plurality of grinding grains each having a rectangular parallelepiped shape and discretely arranged along the circumferential direction of the wheel base. Each of the plurality of grinding grains includes a binder and abrasive grains dispersed inside the binder and held by the binder.

[0005] In this grinding apparatus, generally, a workpiece is held on a chuck table via a protective tape for protecting a device formed on the surface of the workpiece (see, for example, Patent Document 1). Then, with both the chuck table and a spindle having a grinding wheel attached to its tip rotating, the back surface (upper surface) of the workpiece is ground by bringing the grinding surfaces (lower surfaces) of the plurality of grinding wheels into contact with the back surface (upper surface) of the workpiece.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] When a hard structure such as a wafer made of silicon carbide (SiC) or sapphire (Al 2 O 3 ) is exposed on the back surface side of the workpiece, with the grinding of the workpiece, the wear (blunting) of the abrasive grains exposed on the grinding surfaces (lower surfaces) of the plurality of grinding wheels becomes severe. In this case, there is a possibility that problems such as an increase in the drive current of a motor that rotates a grinding wheel including a plurality of grinding wheels via a spindle may occur.

[0008] Therefore, in such a case, it is necessary to promote self-sharpening (where the bonding material on the grinding surface side is ground away and new abrasive grains are exposed on the grinding surface) of each of the plurality of grinding wheels accompanying the grinding of the workpiece. To promote self-sharpening, for example, a brittle material may be applied as the bonding material contained in each of the plurality of grinding wheels. However, in this case, the holding force of the bonding material that holds the abrasive grains becomes weak, and there is a possibility that the grinding of the workpiece becomes difficult.

[0009] In view of this point, an object of the present invention is to provide a method for grinding a workpiece that can promote the self-generated cutting edges of each of a plurality of grinding wheels without weakening the holding force of the binder that holds the abrasive grains.

Means for Solving the Problems

[0010] According to the present invention, there is provided a groove forming step of forming an annular groove that is concentric with the disk-shaped workpiece and has a depth shallower than the difference between the original thickness and the finished thickness of the workpiece on the grinding surface of the workpiece, and after the groove forming step, both the workpiece and an annular grinding wheel in which a plurality of grinding wheels are discretely arranged and which has an outer diameter longer than the radius of the workpiece are rotated, and by bringing the grinding surfaces of each of the plurality of grinding wheels into contact with the grinding surface of the workpiece, there is provided a method for grinding a workpiece, comprising a grinding step of grinding the grinding surface side of the workpiece so that the entire area of the workpiece becomes the finished thickness.

[0011] Preferably, the grinding step includes a rough grinding step of grinding the grinding surface side of the workpiece using an annular rough grinding wheel in which a plurality of rough grinding wheels each containing rough grinding abrasive grains are discretely arranged, and after the rough grinding step, a finish grinding step of grinding the grinding surface side of the workpiece so that the workpiece reaches the finished thickness using an annular finish grinding wheel in which a plurality of finish grinding wheels each containing finish grinding abrasive grains are discretely arranged.

[0012] Preferably, the groove forming step includes a cutting step of cutting the cutting blade into the grinding surface side of the workpiece along a direction perpendicular to the grinding surface of the workpiece with the annular cutting blade rotating, and after the cutting step, a rotating step of rotating the workpiece at least once along the circumferential direction of the workpiece with the cutting blade rotating.

[0013] Alternatively, the groove forming step is performed by bringing the grinding surfaces of the plurality of groove forming grinding wheels, which are discretely arranged and have an outer diameter longer than the radius of the workpiece and shorter than the diameter of the workpiece, into contact with the grinding surface of the workpiece while both the workpiece and the annular groove forming grinding wheel are rotating.

Advantages of the Invention

[0014] In the present invention, after forming an annular groove in the grinding surface of the workpiece, the grinding surface side of the workpiece is ground. In this case, while the regions near the grinding surfaces of the respective side surfaces of the plurality of grinding wheels collide with the side surfaces of the groove formed in the grinding surface of the workpiece, the grinding of the grinding surface side of the workpiece is performed.

[0015] When such a collision occurs, the bonding material on the grinding surface side of the workpiece is easily scraped off. As a result, in the present invention, it is possible to promote the self-generated cutting edges of each of the plurality of grinding wheels without weakening the holding force of the bonding material that holds the abrasive grains.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0017] Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a flowchart schematically showing an example of a method for grinding a workpiece having a large number of devices formed on its surface. In this method, first, an annular groove having a depth shallower than the difference between the original thickness and the finished thickness of the workpiece and concentric with the disk-shaped workpiece is formed in the ground surface of the workpiece (groove forming step: S1).

[0018] FIG. 2 is a flowchart schematically showing an example of the groove forming step (S1). In this groove forming step (S1), after cutting a cutting blade into the ground surface side of the workpiece along a direction perpendicular to the ground surface of the workpiece (cutting step: S11), the workpiece is rotated at least once along the circumferential direction of the workpiece (rotation step: S12).

[0019] FIG. 3 is a perspective view schematically showing an example of a cutting device capable of performing the cutting step (S11) and the rotation step (S12). The X1-axis direction (front-rear direction, machining feed direction) and the Y1-axis direction (left-right direction, indexing feed direction) shown in FIG. 1 are directions perpendicular to each other on a horizontal plane, and the Z1-axis direction (up-down direction) is a direction perpendicular to the X1-axis direction and the Y1-axis direction (vertical direction, cutting feed direction).

[0020] The cutting device 2 shown in FIG. 3 includes a base 4 on which each component is mounted. At the corners of the base 4, a cassette table 8 on which a cassette 6 is placed is installed. In this cassette 6, for example, a frame unit 11 in which a workpiece and an annular frame are integrated via a disk-shaped dicing tape attached to the surface of the workpiece is accommodated.

[0021] This workpiece is, for example, a disk-shaped wafer made of silicon carbide, sapphire, or the like on which a large number of devices are formed on the surface side. The cassette table 8 is connected to a cassette table moving mechanism (not shown) and is movable, for example, along the Z1-axis direction. This cassette table moving mechanism adjusts the height of the cassette 6 placed on the cassette table 8 so that the frame unit 11 can be appropriately carried in and out.

[0022] Also, on the upper part of the base 4, a cover 10 that covers the upper surface side of the base 4 is attached. Inside the cover 10, a cutting unit 12 having a spindle (spindle for cutting blade) to which an annular cutting blade can be attached at the tip is accommodated. This cutting unit 12 is connected to a cutting unit moving mechanism (not shown) and is movable, for example, along the Y1-axis direction and the Z1-axis direction.

[0023] Also, below the cutting unit 12, a chuck table 14 capable of sucking and holding the frame unit 11 is provided. This chuck table 14 is connected to a chuck table moving mechanism (not shown) and is movable, for example, along the X1-axis direction. The chuck table 14 is also connected to a rotation mechanism (not shown) and is rotatable about a straight line substantially parallel to the Z1-axis direction as the rotation axis.

[0024] Furthermore, a touch panel 16 serving as a user interface is provided on the side surface 10a of the cover 10. A warning lamp (pilot lamp) 18 is provided on the upper surface 10b of the cover 10. And the components of the above-described cutting device 2 are connected to a control unit (not shown).

[0025] This control unit has a central processing unit (CPU) and a storage device including a main storage device (volatile memory) and an auxiliary storage device (non-volatile memory), and controls the operations of the components of the cutting device 2 described above. For example, the control unit rotates the spindle of the cutting unit 12 and moves the cutting unit 12 and / or the chuck table 14 so that the workpiece held on the chuck table 14 is cut.

[0026] Each of FIGS. 4(A) and 4(B) is a partial cross-sectional side view schematically showing a state of forming a groove in the back surface (surface to be ground) of the workpiece using the cutting device 2. When forming this groove, first, the frame unit 11 is transported from the cassette 6 to the chuck table 14 so that the center of the workpiece 15 and the center of the chuck table 14 overlap via the dicing tape 13 attached to the surface 15a.

[0027] Next, the chuck table 14 is operated to suck and hold the workpiece 15 via the dicing tape 13. Next, the cutting unit 12 and / or the chuck table 14 are moved so that the cutting blade 20 of the cutting unit 12 is positioned directly above the intermediate region between the center and the outer periphery of the workpiece 15.

[0028] Next, while rotating the spindle (spindle for the cutting blade) 22 of the cutting unit 12, the cutting blade 20 is lowered from the back surface 15b of the workpiece 15 to a depth where the lower end reaches a depth shallower than the difference between the original thickness and the finish thickness of the workpiece 15 (see FIG. 4(A)). Next, while keeping the spindle 22 rotating, the chuck table 14 is rotated at least once (FIG. 4(B)). Thereby, an annular groove 17 that is concentric with the workpiece 15 and has a depth shallower than the difference between the original thickness and the finish thickness of the workpiece 15 is formed in the back surface 15b of the workpiece 15.

[0029] In the method for grinding a workpiece shown in FIG. 1, after the groove forming step (S1), the back surface (the surface to be ground) side of the workpiece 15 is ground so that the entire area of the workpiece 15 reaches the finish thickness (grinding step: S2). FIG. 5 is a flowchart schematically showing an example of the grinding step (S2). In this grinding step (S2), after rough grinding the back surface (the surface to be ground) 15b side of the workpiece 15 (rough grinding step: S21), finish grinding of the back surface (the surface to be ground) 15b side of the workpiece 15 is performed (finish grinding step: S22).

[0030] FIG. 6 is a perspective view schematically showing an example of a grinding apparatus capable of performing the rough grinding step (S21) and the finish grinding step (S22). The X2-axis direction (front-rear direction) and the Y2-axis direction (left-right direction) shown in FIG. 6 are directions perpendicular to each other on a horizontal plane, and the Z2-axis direction (vertical direction) is a direction perpendicular to the X2-axis direction and the Y2-axis direction (vertical direction).

[0031] The grinding apparatus 24 shown in FIG. 6 includes a base 26 on which each component is mounted. An opening 26a is formed on the front end side of the upper surface of the base 26, and a transfer mechanism 28 is provided in the opening 26a. This transfer mechanism 28 is, for example, a robot arm having a plurality of joints. In front of the opening 26a, cassette mounting tables 32a, 32b on which cassettes 30a, 30b are placed are provided.

[0032] In these cassettes 30a, 30b, for example, after separating the dicing tape 13 from the surface 15a of the workpiece 15 having the groove 17 formed on the back surface 15b, the workpiece 15 with a new film-like protective tape attached to the surface 15a is accommodated. This protective tape prevents the devices formed on the surface 15a of the workpiece 15 from being damaged when the back surface 15b side of the workpiece 15 is ground.

[0033] In addition, the transfer mechanism 28 can not only hold and transfer the workpiece 15, but also invert the workpiece 15 up and down. Further, a position adjustment mechanism 34 for adjusting the position of the workpiece 15 is provided diagonally rearward of the opening 26a. The position adjustment mechanism 34 includes, for example, a disk-shaped table and a plurality of pins arranged around the table.

[0034] The transfer mechanism 28, for example, takes out the workpiece 15 from the cassette 30a and transfers the workpiece 15 to the table of the position adjustment mechanism 34 so that the back surface 15b faces upward. Then, by moving a plurality of pins along the radial direction of this table, for example, the center of the workpiece 15 carried into the table of the position adjustment mechanism 34 is aligned with a predetermined position (coordinates) in a plane (X2Y2 coordinate plane) parallel to the X2-axis direction and the Y2-axis direction.

[0035] A transfer mechanism 36 for transferring the workpiece 15 is provided behind the transfer mechanism 28 and the position adjustment mechanism 34. Further, a disk-shaped turntable 38 is provided behind the transfer mechanism 36. This turntable 38 is connected to a rotational drive source (not shown) such as a motor and rotates about a straight line substantially parallel to the Z2-axis direction as the rotation axis.

[0036] In addition, three chuck tables 40 capable of holding the workpiece 15 are provided on the upper surface of the turntable 38. The three chuck tables 40 are provided at substantially equal intervals along the circumferential direction of the turntable 38. Note that there is no limitation on the number of chuck tables 40 provided on the turntable 38.

[0037] FIG. 7 is a plan view schematically showing the turntable 38 and the structure around it. In FIG. 7, for convenience of explanation, some elements are represented by broken lines. The transfer mechanism 36 takes out the workpiece 15 aligned in the position adjustment mechanism 34 from the position adjustment mechanism 34 and transfers it to the chuck table 40 arranged in the loading / unloading area A adjacent to the transfer mechanism 36.

[0038] The turntable 38 rotates in the direction indicated by the arrow in FIGS. 6 and 7, for example, and moves the three chuck tables 40 in the order of the loading / unloading area A, the rough grinding area B, and the finish grinding area C. Each of the three chuck tables 40 is connected to a rotational drive source (not shown) such as a motor and rotates about an axis of rotation that is a straight line substantially parallel to the Z2-axis direction.

[0039] This chuck table 40 has, for example, a disk-shaped frame made of ceramics or the like. And a recess having a circular opening at the upper end is formed on the upper surface side of this frame, and a disk-shaped porous plate made of ceramics or the like is fixed to this recess.

[0040] Also, the upper surface of the chuck table 40 is configured in a shape corresponding to the side surface of a cone whose center protrudes slightly more than the outer edge, and functions as a holding surface 40a for holding the surface 15a side of the workpiece 15. That is, each chuck table 40 is provided with a holding surface 40a for holding the workpiece 15 at the upper part.

[0041] Specifically, this holding surface 40a communicates with a suction source (not shown) such as a vacuum pump via a suction path (not shown) formed inside the chuck table 40. When this suction source is operated, a suction force acts on the space near the holding surface 40a. Therefore, when this suction source is operated with the surface 15a side of the workpiece 15 placed on the holding surface 40a, the workpiece 15 is sucked and held by the chuck table 40.

[0042] Also, a columnar support structure 42 is provided behind each of the rough grinding area B and the finish grinding area C (see FIG. 6). A Z2-axis movement mechanism 44 is provided on the front side of each support structure 42. This Z2-axis movement mechanism 44 includes a pair of guide rails 46 substantially parallel to the Z2-axis direction.

[0043] On the front side of the pair of guide rails 46, a moving plate 48 is attached in a slidable manner. On the rear surface (back surface) side of this moving plate 48, a nut portion (not shown) constituting a ball screw is fixed, and a screw shaft 50 substantially parallel to the guide rail 46 is connected to this nut portion in a rotatable manner.

[0044] A motor 52 is connected to the upper end portion of this screw shaft 50. By rotating the screw shaft 50 with the motor 52, the moving plate 48 moves along the Z2-axis direction along the guide rail 46. Also, a fixture 54 is provided on the front (surface) side of the moving plate 48. This fixture 54 supports a grinding unit 56, and this grinding unit 56 includes a spindle housing 58 fixed to the fixture 54.

[0045] A spindle (grinding wheel spindle) 60 is accommodated in this spindle housing 58 in a rotatable manner with a straight line substantially parallel to the Z2-axis direction as the rotation axis. The lower end portion of this spindle 60 is exposed from the lower end surface of the spindle housing 58, and a disk-shaped mount 62 is fixed to the lower end portion of this spindle 60.

[0046] On the lower surface of the mount 62 of the grinding unit 56 on the rough grinding region B side, a rough grinding wheel 64 is mounted. This rough grinding wheel 64 is made of a metal material such as stainless steel or aluminum, and has an annular rough grinding wheel base having an outer diameter substantially equal to the diameter of the mount 62. Also, both the inner diameter and the outer diameter of the rough grinding wheel 64 are longer than the radius of the workpiece 15 described above.

[0047] On the lower surface of this rough grinding wheel base, a plurality of rough grinding wheels formed by fixing rough grinding abrasive grains such as diamond suitable for rough grinding with a bond such as vitrified or resinoid are discretely arranged. Also, in the spindle housing 58 of the grinding unit 56 on the rough grinding region B side, a rough grinding rotation drive source (not shown) such as a motor connected to the upper end side of the spindle 60 is accommodated.

[0048] When the rough grinding rotary drive source operates, the grinding wheel 64 for rough grinding rotates together with the spindle 60. At this time, the grinding stones for rough grinding included in the grinding wheel 64 for rough grinding draw an annular locus whose outer and inner diameters are both longer than the radius of the workpiece 15. In addition, this locus overlaps with the center of the holding surface 40a of the chuck table 40 positioned in the rough grinding region B.

[0049] Furthermore, a liquid supply nozzle (not shown) capable of supplying liquid (grinding fluid) such as pure water to a contact point (processing point) between the back surface 15b of the workpiece 15 and the lower surfaces (grinding surfaces) of the grinding wheels for rough grinding is provided near the grinding wheel for rough grinding 64. However, instead of or together with this liquid supply nozzle, a liquid supply port used for supplying liquid may be provided in the grinding wheel for rough grinding 64.

[0050] Similarly, a grinding wheel 66 for finish grinding is attached to the lower surface of the mount 62 of the grinding unit 56 on the finish grinding area C side. The grinding wheel 66 for finish grinding is made of a metal such as stainless steel or aluminum, and is provided with an annular finish grinding wheel base whose outer diameter is approximately equal to the diameter of the mount 62. In addition, both the inner diameter and the outer diameter of the grinding wheel 66 for finish grinding are longer than the radius of the workpiece 15.

[0051] A plurality of grinding stones for finish grinding, each made of abrasive grains for finish grinding such as diamond suitable for finish grinding (for example, abrasive grains having an average grain size finer than that of abrasive grains for coarse grinding) fixed with a bond such as vitrified or resinoid, are arranged in a dispersed manner on the underside of the wheel base for finish grinding. A rotation drive source for finish grinding such as a motor (not shown) connected to the upper end side of the spindle 60 is accommodated in the spindle housing 58 of the grinding unit 56 on the finish grinding area C side.

[0052] When the rotary drive source for finish grinding operates, the finish grinding wheel 66 rotates together with the spindle 60. At this time, the plurality of finish grinding wheels included in the finish grinding wheel 66 draw an annular locus whose outer diameter and inner diameter are both longer than the radius of the workpiece 15. Further, this locus overlaps with the center of the holding surface 40a of the chuck table 40 positioned in the finish grinding region C.

[0053] Furthermore, beside the finish grinding wheel 66, a liquid supply nozzle (not shown) for supplying a liquid (grinding fluid) such as pure water is provided at the contact point (processing point) between the back surface 15b of the workpiece 15 and the lower surface (grinding surface) of the plurality of finish grinding wheels. However, instead of this liquid supply nozzle, or together with the liquid supply nozzle, a liquid supply port used for supplying the liquid may be provided on the finish grinding wheel 66.

[0054] The workpiece 15 held by the chuck table 40 is sequentially ground by the above-described two sets of grinding units 56. Specifically, the workpiece 15 is ground by the grinding unit 56 on the rough grinding region B side in the rough grinding region B and then ground by the grinding unit 56 on the finish grinding region C side in the finish grinding region C.

[0055] Furthermore, a transport mechanism 68 for transporting the workpiece 15 after grinding is provided in front of the loading / unloading region A and on the side of the transport mechanism 36. In front of the transport mechanism 68, a cleaning unit 70 for cleaning the workpiece 15 unloaded from the chuck table 40 by the transport mechanism 68 is provided.

[0056] This cleaning unit 70 includes, for example, a spinner table that rotates while holding the surface 15a side of the workpiece 15, and a nozzle that injects a cleaning fluid onto the back surface (ground surface) 15b side of the workpiece 15 held by the spinner table. The workpiece 15 cleaned by this cleaning unit 70 is transported from the cleaning unit 70 by the transport mechanism 28 and loaded into, for example, the cassette 30b.

[0057] Furthermore, the grinding device 24 may include components other than the above-described components. For example, the grinding device 24 may include a touch panel configured by a touch sensor that inputs instructions from an operator to the grinding device 24 and a display that outputs various types of information to the operator. And the components of the grinding device 24 described above are connected to a control unit (not shown).

[0058] This control unit has a central processing unit (CPU) and a storage device including a main storage device (volatile memory) and an auxiliary storage device (non-volatile memory), and controls the operations of the components of the grinding device 24 described above. For example, the control unit controls the above-described components so that the workpiece 15 held on the chuck table 40 changes from the original thickness to the finished thickness.

[0059] Each of FIGS. 8(A) and 8(B) is a partial cross-sectional side view schematically showing a state in which the back surface 15b side of the workpiece 15 is ground using the grinding device 24. At the time of this grinding, first, the transfer mechanism 28 takes out the workpiece 15 from the cassette 30a and transfers it onto the upper surface of the disk-shaped table of the positioning mechanism 34 so that the back surface 15b of the workpiece 15 faces upward. Thereby, the workpiece 15 is supported by the table via the protective tape 19 attached to the surface 15a thereof.

[0060] Next, by moving a plurality of pins arranged around the table along the radial direction of the table, the center position of the workpiece 15 is positioned at specific coordinates in the X2Y2 coordinate plane. Next, the transfer mechanism 36 takes out the workpiece 15 from the table of the positioning mechanism 34 and transfers it onto the holding surface 40a of the chuck table 40 positioned in the loading / unloading area A. Thereby, the workpiece 15 is supported by the chuck table 40 via the protective tape 19.

[0061] Next, the chuck table 40 is operated to suck and hold the surface 15a side of the workpiece 15 via the protective tape 19. Next, the turntable 38 is rotated so as to position the chuck table 40 holding the workpiece 15 in the rough grinding region B. Next, both the chuck table 40 positioned in the rough grinding region B and the spindle 60 of the grinding unit 56 on the rough grinding region B side are rotated.

[0062] Also, along with the rotation of the spindle 60, the mount 62 and the rough grinding wheel 64 rotate along the circumferential direction of the rough grinding wheel 64 (rough grinding wheel base 64a). Next, while the chuck table 40 and the rough grinding wheel 64 are rotating, the grinding unit 56 on the rough grinding region B side is lowered so that the lower surfaces (grinding surfaces) of the plurality of rough grinding wheels 64b contact the back surface 15b of the workpiece 15 (see Fig. 8(A)).

[0063] Thereby, the back surface 15b side of the workpiece 15 is ground and removed by the lower sides of the plurality of rough grinding wheels 64b. And this grinding (rough grinding) is continued until the thickness of the workpiece 15 becomes a predetermined thickness that is thicker than the finish thickness. For example, the rough grinding is continued until the depth of the groove 17 formed in the back surface 15b of the workpiece 15 becomes 1 / 3 times to 1 / 10 times.

[0064] Next, the rotation of both the chuck table 40 positioned in the rough grinding region B and the spindle 60 of the grinding unit 56 on the rough grinding region B side is stopped, and the grinding unit 56 is raised. Next, the turntable 38 is rotated so as to position the chuck table 40 holding the workpiece 15 in the finish grinding region C. Next, both the chuck table 40 positioned in the finish grinding region C and the spindle 60 of the grinding unit 56 on the finish grinding region C side are rotated.

[0065] Further, as the spindle 60 rotates, the mount 62 and the finish grinding wheel 66 rotate along the circumferential direction of the finish grinding wheel 66 (finish grinding wheel base 66a). Next, while the chuck table 40 and the finish grinding wheel 66 are rotating, the grinding unit 56 on the finish grinding region C side is lowered so that the lower surfaces (grinding surfaces) of the plurality of finish grinding wheels 66b contact the back surface 15b of the workpiece 15 (see FIG. 8(B)).

[0066] As a result, the back surface 15b side of the workpiece 15 is ground and removed by the plurality of finish grinding wheels 66b. And this grinding (finish grinding) is continued until the thickness of the workpiece 15 becomes the finish thickness. That is, the groove 17 formed on the back surface 15b of the workpiece 15 by the finish grinding disappears. As a result, the entire area of the workpiece 15 becomes the finish thickness.

[0067] In the above-described grinding method of the workpiece, after forming the annular groove 17 on the back surface 15b of the workpiece 15, the back surface 15b side of the workpiece 15 is ground. In this case, while the regions near the lower surfaces of the side surfaces of the plurality of grinding wheels (coarse grinding wheel 64b and finish grinding wheel 66b) collide with the regions near the upper surfaces of the side surfaces of the groove 17 formed on the back surface 15b of the workpiece 15, the back surface 15b side of the workpiece 15 is ground.

[0068] When such a collision occurs, the bonding material on the lower surface side of the workpiece 15 is easily scraped off. As a result, in the above-described grinding method of the workpiece, without weakening the holding force of the bonding material that holds the abrasive grains (coarse grinding abrasive grains and finish grinding abrasive grains), the self-generated cutting edges of the plurality of grinding wheels (coarse grinding wheel 64b and finish grinding wheel 66b) can be promoted.

[0069] Note that the above-described content is one aspect of the present invention, and inventions having features different from the above-described content are also included in the present invention. For example, in the groove forming step of the present invention, a groove may be formed on the back surface 15b of the workpiece 15 using grinding, plasma etching, or laser ablation.

[0070] Each of FIG. 9(A) and FIG. 9(B) is a partial cross-sectional side view schematically showing a state of forming a groove in the back surface (surface to be ground) 15b of the workpiece 15 using a grinding device. The grinding device 72 shown in each of FIG. 9(A) and FIG. 9(B) has a chuck table 74. This chuck table 74 has, for example, a disk-shaped frame made of ceramics or the like.

[0071] And, a recess having a circular opening at the upper end is formed on the upper surface side of this frame, and a disk-shaped porous plate made of ceramics or the like is fixed in this recess. Further, the upper surface of the chuck table 74 is configured in a shape corresponding to the side surface of a cone whose center slightly protrudes from the outer edge, and functions as a holding surface 74a for holding the surface 15a side of the workpiece 15.

[0072] Specifically, this holding surface 74a communicates with a suction source (not shown) such as a vacuum pump via a suction passage (not shown) formed inside the chuck table 74. When this suction source is operated, a suction force acts on the space near the holding surface 74a. Therefore, when the suction source is operated with the surface 15a side of the workpiece 15 placed on the holding surface 74a, the workpiece 15 is sucked and held by the chuck table 74.

[0073] Furthermore, the chuck table 74 is connected to a chuck table moving mechanism (not shown) and is movable along the horizontal direction. Also, above the chuck table 74, a grinding unit 76 is provided. This grinding unit 76 has a spindle 78 that can rotate with a straight line substantially parallel to the vertical direction as the rotation axis.

[0074] And, a disk-shaped mount 80 is fixed to the lower end portion of the spindle 78. Also, a groove-forming grinding wheel 82 is mounted on the lower surface of the mount 80. This groove-forming grinding wheel 82 is made of a metal material such as stainless steel or aluminum, and includes an annular groove-forming wheel base 82a having an outer diameter substantially equal to the diameter of the mount 80.

[0075] Further, both the inner diameter and the outer diameter of the grinding wheel 82 for groove formation are longer than the radius of the workpiece 15 described above and shorter than the diameter of the workpiece 15. On the lower surface of the groove formation wheel base 82a, a plurality of grinding wheels 82b for groove formation, in which abrasive grains for groove formation such as diamond are fixed with a bond such as vitrified or resinoid, are discretely arranged.

[0076] In addition, when both the inner diameter and the outer diameter of the grinding wheels (rough grinding wheel 64 and finish grinding wheel 66) used in the grinding step of the present invention are shorter than the diameter of the workpiece 15, the grinding wheel 82 for groove formation may be the same as this grinding wheel (for example, the rough grinding wheel 64).

[0077] Furthermore, the upper end portion of the spindle 78 is connected to a rotational drive source (not shown) such as a motor. When the rotational drive source operates, the grinding wheel 82 for groove formation rotates together with the spindle 78. At this time, the plurality of grinding wheels 82b for groove formation included in the grinding wheel 82 for groove formation draw an annular locus whose both the outer diameter and the inner diameter are longer than the radius of the workpiece 15 described above and shorter than the diameter of the workpiece 15.

[0078] Furthermore, beside the grinding wheel 82 for groove formation, a liquid supply nozzle (not shown) capable of supplying a liquid (grinding fluid) such as pure water to the contact point (processing point) between the back surface 15b of the workpiece 15 and the lower surface (grinding surface) of the plurality of grinding wheels 82b for groove formation is provided. However, instead of this liquid supply nozzle, or together with the liquid supply nozzle, a liquid supply port used for supplying the liquid may be provided in the grinding wheel 82 for groove formation.

[0079] When forming a groove in the back surface (surface to be ground) 15b of the workpiece 15 using the grinding device 72, first, the workpiece 15 is conveyed to the chuck table 74 so that the center of the workpiece 15 and the center of the chuck table 74 overlap via the protective tape 19 attached to the surface 15a.

[0080] Next, the chuck table 74 is operated to suck and hold the surface 15a side of the workpiece 15 via the protective tape 19. Next, the chuck table 74 is moved so that the straight line that becomes the rotation axis of the spindle 78 (the rotation axis of the groove-forming grinding wheel 82) passes through the center of the holding surface 74a of the chuck table 74. Next, both the chuck table 74 and the spindle 78 are rotated.

[0081] Next, while the chuck table 74 and the groove-forming grinding wheel 82 are rotating, the grinding unit 76 is lowered so that the lower surfaces (grinding surfaces) of the plurality of groove-forming grinding wheels 82b contact the back surface (surface to be ground) 15b of the workpiece 15. Thereby, the annular region on the back surface 15b side of the workpiece 15 is ground and removed by the lower sides of the plurality of groove-forming grinding wheels 82b.

[0082] Then, this grinding is continued until the distance between the lower surface of the plurality of groove-forming grinding wheels 82b and the surface 15a of the workpiece 15 becomes a predetermined length that is greater than a predetermined thickness that is greater than the finished thickness of the workpiece 15 (see FIG. 9(A)). Next, the rotation of both the chuck table 74 and the spindle 78 is stopped, and the grinding unit 76 is raised (see FIG. 9(B)). Thereby, an annular groove 21 having a depth that is concentric with the workpiece 15 and shallower than the difference between the original thickness and the finished thickness of the workpiece 15 is formed on the back surface 15b of the workpiece 15.

[0083] Also, the groove-forming step and the grinding step of the present invention may be carried out in a single grinding apparatus in which the relative positional relationship between the grinding unit and the chuck table can be arbitrarily changed. Specifically, in this grinding apparatus, the grinding unit and / or the chuck table are connected to a ball screw type horizontal movement mechanism.

[0084] By operating this horizontal movement mechanism, the grinding unit and the chuck table can be relatively moved so as to switch between a state where the straight line that becomes the rotation axis of the grinding wheel passes through the center of the holding surface of the chuck table and a state where the locus drawn by the rotating grinding wheel overlaps with the center of the holding surface of the chuck table.

[0085] In addition, the structures, methods, etc. according to the above-described embodiments can be appropriately changed and implemented without departing from the scope of the object of the present invention.

Explanation of Signs

[0086] 2: Cutting device 4: Base 6: Cassette table 8: Cassette 10: Cover (10a: Side surface, 10b: Upper surface) 11: Frame unit 12: Cutting unit 13: Dicing tape 14: Chuck table 15: Workpiece (15a: Surface, 15b: Back surface (surface to be ground)) 16: Touch panel 17: Groove 18: Warning light (pilot lamp) 19: Protection tape 20: Cutting blade 21: Groove 22: Spindle (spindle for cutting blade) 24: Grinding device 26: Base (26a: Opening) 28: Conveying mechanism 30a, 30b: Cassette 32a, 32b: Cassette mounting table 34: Position adjusting mechanism 36: Conveying mechanism 38: Turntable 40: Chuck table (40a: Holding surface) 42: Support structure 44: Z2-axis movement mechanism 46: Guide rail 48: Moving plate 50: Screw shaft 52: Motor 54: Fixture 56: Grinding unit 58: Spindle housing 60: Spindle (spindle for grinding wheel) 62: Mount 64: Rough grinding wheel (64a: Wheel base for rough grinding, 64b: Grinding stone for rough grinding) 66: Finish grinding wheel (66a: Wheel base for finish grinding, 66b: Grinding stone for finish grinding) 68: Conveyor mechanism 70: Cleaning unit 72: Grinding device 74: Chuck table (74a: Holding surface) 76: Grinding unit 78: Spindle 80: Mount 82: Groove-forming grinding wheel (82a: Wheel base for groove forming, 82b: Grinding stone for groove forming)

Claims

1. A groove forming step of forming an annular groove that is concentric with the disk-shaped workpiece and has a depth shallower than the difference between the original thickness and the finished thickness of the workpiece on the grinding surface of the workpiece; After the groove forming step, with both the workpiece and an annular grinding wheel in which a plurality of grinding grains are discretely arranged and which has an outer diameter longer than the radius of the workpiece rotating, by bringing the grinding surfaces of the respective grinding grains into contact with the grinding surface of the workpiece, a grinding step of grinding the grinding surface side of the workpiece so that the entire area of the workpiece becomes the finished thickness; A method for grinding a workpiece, comprising the above.

2. The grinding step includes: A rough grinding step of grinding the grinding surface side of the workpiece using an annular rough grinding wheel in which a plurality of rough grinding grains each containing rough grinding grains are discretely arranged; After the rough grinding step, a finish grinding step of grinding the grinding surface side of the workpiece using an annular finish grinding wheel in which a plurality of finish grinding grains each containing finish grinding grains are discretely arranged so that the workpiece reaches the finished thickness; The method for grinding a workpiece according to Claim 1, characterized by including the above.

3. The groove forming step includes: A cutting step of cutting the cutting blade into the grinding surface side of the workpiece along a direction perpendicular to the grinding surface of the workpiece with the annular cutting blade rotating; After the cutting step, a rotating step of rotating the workpiece at least once along the circumferential direction of the workpiece with the cutting blade rotating; The method for grinding a workpiece according to Claim 1 or 2, characterized by including the above.

4. The groove forming step is performed by bringing the grinding surfaces of a plurality of groove forming grinding grains into contact with the grinding surface of the workpiece with both the workpiece and an annular groove forming grinding wheel in which the plurality of groove forming grinding grains are discretely arranged and which has an outer diameter longer than the radius of the workpiece and shorter than the diameter of the workpiece rotating. The method for grinding a workpiece according to Claim 1 or 2, characterized by the above.

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