JP7684178B2 - Method for grinding a workpiece - Google Patents

Description

The present invention relates to a method for grinding a disk-shaped workpiece, in which the grinding surface of the workpiece is ground so that the entire area of the workpiece has a finishing thickness.

Chips for 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 on which many devices are formed into areas containing individual devices.

Furthermore, the workpiece is often thinned before being divided in order to reduce the size and weight of the chips. The workpiece is thinned, for example, by grinding the back side of the workpiece in a grinding device. Such a grinding device has a holding surface (upper surface) shaped to correspond to the side surface of the cone, and is equipped with a chuck table that can rotate around a straight line passing through the center of this holding surface as the rotation axis.

Above the chuck table, a grinding unit is provided that has a spindle to which an annular grinding wheel can be attached. The grinding wheel includes an annular wheel base and a plurality of grinding wheels, each of which has a rectangular parallelepiped shape and is arranged in a dispersed manner along the circumferential direction of the wheel base. Each of the grinding wheels includes a binder and abrasive grains that are dispersed within the binder and held by the binder.

In this grinding device, the workpiece is generally held on the chuck table via a protective tape to protect the device formed on the surface of the workpiece (see, for example, Patent Document 1). Then, while both the chuck table and a spindle with a grinding wheel attached to its tip are rotating, the grinding surfaces (lower surfaces) of the multiple grinding wheels are brought into contact with the back surface (upper surface) of the workpiece, thereby grinding the back surface of the workpiece.

JP 2003-209080 A

When a hard structure such as a wafer made of silicon carbide (SiC) or sapphire (Al ₂ O ₃ ) is exposed on the back side of a workpiece, the abrasive grains exposed on the grinding surface (lower surface) of each of the grinding wheels become worn (glazed) rapidly as the workpiece is ground. In this case, there is a risk of a problem such as an increase in the drive current of a motor that rotates a grinding wheel including the grinding wheels via a spindle.

Therefore, in such cases, it is necessary to promote the self-sharpening of each of the multiple grinding wheels as the workpiece is ground (the binder on the grinding surface is scraped off, exposing new abrasive grains on the grinding surface). In order to promote the self-sharpening of the edge, for example, a brittle material may be used as the binder contained in each of the multiple grinding wheels. However, in this case, the holding power of the binder that holds the abrasive grains may be weakened, making it difficult to grind the workpiece.

In view of this, the object of the present invention is to provide a method for grinding a workpiece that can promote the spontaneous sharpening of each of multiple grinding wheels without weakening the holding power of the binder that holds the abrasive grains.

According to the present invention, there is provided a method for grinding a workpiece, comprising: a groove forming step for forming an annular groove on the grinding surface of a disk-shaped workpiece, the groove being concentric with the workpiece and shallower than the difference between the original thickness and the finished thickness of the workpiece; and a grinding step for grinding the grinding surface side of the workpiece so that the entire area of the workpiece has the finished thickness by contacting the grinding surfaces of the grinding wheels with the grinding surface of the workpiece after the groove forming step, while both the workpiece and an annular grinding wheel having a discretely arranged grinding wheel and an outer diameter longer than the radius of the workpiece are rotating.

Preferably, the grinding step includes a rough grinding step of grinding the grinding surface side of the workpiece using an annular rough grinding grinding wheel on which a plurality of rough grinding grinding stones each containing abrasive grains for rough grinding are arranged in a discrete manner, and a finish grinding step of grinding the grinding surface side of the workpiece to the finishing thickness using an annular finish grinding grinding wheel on which a plurality of finish grinding grinding stones each containing abrasive grains for finish grinding are arranged in a discrete manner after the rough grinding step.

Preferably, the groove forming step includes a cutting step in which, while the annular cutting blade is rotating, the cutting blade is caused to cut into the grinding surface of the workpiece in a direction perpendicular to the grinding surface of the workpiece, and a rotation step in which, after the cutting step, the workpiece is rotated at least once along the circumferential direction of the workpiece while the cutting blade is rotating.

Alternatively, the groove forming step is performed by contacting the grinding surface of each of the groove forming grinding wheels with the grinding surface of the workpiece while both the workpiece and a circular groove forming grinding wheel, on which a plurality of groove forming grinding wheels are arranged in a discrete manner and which has an outer diameter longer than the radius of the workpiece and shorter than the diameter of the workpiece, are rotating.

In the present invention, an annular groove is formed on the grinding surface of the workpiece, and then the grinding surface side of the workpiece is ground. In this case, the grinding surface side of the workpiece is ground while the areas of the side surfaces of the multiple grinding wheels near the grinding surface collide with the side surfaces of the grooves formed on the grinding surface of the workpiece.

When such a collision occurs, the binder on the grinding surface of the workpiece is easily chipped. As a result, the present invention can promote the spontaneous sharpening of each of the multiple grinding wheels without weakening the holding power of the binder that holds the abrasive grains.

FIG. 1 is a flow chart that illustrates an example of a method for grinding a workpiece. FIG. 2 is a flow chart showing a schematic example of the groove forming step. FIG. 3 is a perspective view illustrating an example of a cutting device. 4A and 4B are each a partially sectional side view that shows a schematic diagram of a state in which a groove is formed on a ground surface of a workpiece by using a cutting device. FIG. 5 is a flow chart illustrating an example of the grinding step. FIG. 6 is a perspective view illustrating an example of a grinding device. FIG. 7 is a plan view showing a schematic diagram of the turntable and its surrounding structure. 8A and 8B are each a partially sectional side view that typically shows how the grinding device is used to grind the grinding surface side of a workpiece. 9(A) and 9(B) are each a partially sectional side view that typically shows how a groove is formed on a grinding surface of a workpiece using a grinding device.

An embodiment of the present invention will be described with reference to the attached drawings. FIG. 1 is a flow chart showing a schematic example of a method for grinding a workpiece having a number of devices formed on its surface. In this method, first, an annular groove is formed on the grinding surface of the workpiece, which 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 (groove formation step: S1).

Figure 2 is a flow chart showing a schematic example of the groove forming step (S1). In this groove forming step (S1), the cutting blade is cut into the grinding surface of the workpiece in a direction perpendicular to the grinding surface of the workpiece (cutting step: S11), and then the workpiece is rotated at least once in the circumferential direction of the workpiece (rotation step: S12).

Figure 3 is a perspective view showing a schematic example of a cutting device capable of performing the cutting step (S11) and the rotation step (S12). Note that the X1 axis direction (front-back direction, machining feed direction) and the Y1 axis direction (left-right direction, indexing feed direction) shown in Figure 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).

The cutting device 2 shown in FIG. 3 has a base 4 on which each component is mounted. A cassette table 8 on which a cassette 6 is placed is installed at a corner of the base 4. This cassette 6 contains a frame unit 11 in which the workpiece and an annular frame are integrated together, for example, via a disk-shaped dicing tape attached to the surface of the workpiece.

The workpiece is, for example, a disk-shaped wafer made of silicon carbide or sapphire with a large number of devices formed on the surface side. The cassette table 8 is connected to a cassette table moving mechanism (not shown) and can move, 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 loaded and unloaded.

A cover 10 is attached to the top of the base 4, covering the upper surface of the base 4. Inside the cover 10, a cutting unit 12 is housed, which has a spindle (spindle for cutting blade) to the tip of which an annular cutting blade can be attached. This cutting unit 12 is connected to a cutting unit movement mechanism (not shown), and can move, for example, along the Y1 axis and Z1 axis directions.

In addition, a chuck table 14 capable of holding the frame unit 11 by suction is provided below the cutting unit 12. This chuck table 14 is connected to a chuck table moving mechanism (not shown) and can move, for example, along the X1 axis direction. In addition, the chuck table 14 is connected to a rotation mechanism (not shown) and can rotate around a rotation axis that is a straight line roughly parallel to the Z1 axis direction.

Furthermore, a touch panel 16 that serves as a user interface is provided on the side surface 10a of the cover 10. Also, a warning light (pilot lamp) 18 is provided on the top surface 10b of the cover 10. The above-mentioned components of the cutting device 2 are connected to a control unit (not shown).

The 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 operation 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.

Figures 4(A) and 4(B) are each a partial cross-sectional side view that shows a schematic diagram of how a groove is formed on the back surface (ground surface) of a workpiece using a 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 overlaps with the center of the chuck table 14 via the dicing tape 13 attached to the front surface 15a.

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.

Next, while rotating the spindle (spindle for cutting blade) 22 of the cutting unit 12, the cutting blade 20 is lowered until the bottom end reaches a depth shallower than the difference between the original thickness and the finished thickness of the workpiece 15 from the back surface 15b 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)). As a result, an annular groove 17 is formed on the back surface 15b of the workpiece 15, which is concentric with the workpiece 15 and has a depth shallower than the difference between the original thickness and the finished thickness of the workpiece 15.

In the method for grinding the workpiece shown in FIG. 1, after the groove forming step (S1), the back surface (grinding surface) of the workpiece 15 is ground so that the entire area of the workpiece 15 has a finishing thickness (grinding step: S2). FIG. 5 is a flow chart showing an example of the grinding step (S2). In this grinding step (S2), the back surface (grinding surface) 15b of the workpiece 15 is roughly ground (rough grinding step: S21), and then the back surface (grinding surface) 15b of the workpiece 15 is finish ground (finish grinding step: S22).

Figure 6 is a perspective view showing a schematic example of a grinding device capable of performing the rough grinding step (S21) and the finish grinding step (S22). Note that the X2 axis direction (front-back direction) and the Y2 axis direction (left-right direction) shown in Figure 6 are directions perpendicular to each other on a horizontal plane, and the Z2 axis direction (up-down direction) is a direction (vertical direction) perpendicular to the X2 axis direction and the Y2 axis direction.

The grinding device 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 transport mechanism 28 is provided within the opening 26a. The transport mechanism 28 is, for example, a robot arm with multiple joints. In addition, cassette placement tables 32a and 32b on which cassettes 30a and 30b are placed are provided in front of the opening 26a.

These cassettes 30a and 30b contain workpieces 15 with grooves 17 formed on the back surface 15b, on which a film-like protective tape has been newly attached after the dicing tape 13 has been separated from the front surface 15a of the workpiece 15. This protective tape prevents damage to the devices formed on the front surface 15a of the workpiece 15 when the back surface 15b of the workpiece 15 is ground.

The transport mechanism 28 can not only hold and transport the workpiece 15, but can also turn the workpiece 15 upside down. A position adjustment mechanism 34 for adjusting the position of the workpiece 15 is provided diagonally behind the opening 26a. The position adjustment mechanism 34 includes, for example, a disk-shaped table and multiple pins arranged around the table.

The transport mechanism 28, for example, removes the workpiece 15 from the cassette 30a and loads the workpiece 15 onto the table of the position adjustment mechanism 34 with the back surface 15b facing upward. Then, by moving multiple pins along the radial direction of the table, for example, the center of the workpiece 15 loaded onto the table of the position adjustment mechanism 34 is aligned to a predetermined position (coordinate) on a plane (X2Y2 coordinate plane) parallel to the X2-axis direction and the Y2-axis direction.

A transport mechanism 36 that transports the workpiece 15 is provided behind the transport mechanism 28 and the position adjustment mechanism 34. A disk-shaped turntable 38 is provided behind the transport mechanism 36. The turntable 38 is connected to a rotary drive source (not shown) such as a motor, and rotates around a rotation axis that is a straight line roughly parallel to the Z2 axis direction.

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 approximately equal intervals along the circumferential direction of the turntable 38. There is no limit to the number of chuck tables 40 provided on the turntable 38.

Figure 7 is a plan view showing a schematic diagram of the turntable 38 and its surrounding structure. Note that in Figure 7, some elements are shown by dashed lines for ease of explanation. The transport mechanism 36 transports the workpiece 15, which has been aligned in the position adjustment mechanism 34, out of the position adjustment mechanism 34 and transports it to the chuck table 40, which is located in the load/unload area A adjacent to the transport mechanism 36.

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

The chuck table 40 has a disk-shaped frame made of, for example, ceramics. A recess with a circular opening at the top end is formed on the upper surface of the frame, and a disk-shaped porous plate made of, for example, ceramics is fixed in this recess.

The upper surface of the chuck table 40 is configured in a shape equivalent to the side of a cone whose center protrudes slightly beyond the outer edge, and functions as a holding surface 40a that holds the front surface 15a side of the workpiece 15. In other words, each chuck table 40 has a holding surface 40a at the top that holds the workpiece 15.

Specifically, the holding surface 40a is connected to a suction source (not shown) such as a vacuum pump via a suction passage (not shown) formed inside the chuck table 40. When the suction source is operated, a suction force acts on the space near the holding surface 40a. Therefore, when the 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.

In addition, 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 has a pair of guide rails 46 that are generally parallel to the Z2-axis direction.

A movable plate 48 is attached to the front side of the pair of guide rails 46 in a slidable manner. A nut portion (not shown) constituting a ball screw is fixed to the rear (back) side of this movable plate 48, and a screw shaft 50 that is generally parallel to the guide rails 46 is connected to this nut portion in a rotatable manner.

A motor 52 is connected to the upper end of the screw shaft 50. When the motor 52 rotates the screw shaft 50, the moving plate 48 moves in the Z2-axis direction along the guide rail 46. A fixing device 54 is provided on the front (surface) side of the moving plate 48. The fixing device 54 supports a grinding unit 56, and the grinding unit 56 includes a spindle housing 58 fixed to the fixing device 54.

The spindle housing 58 contains a spindle (spindle for grinding wheels) 60 that can rotate around a rotation axis that is a straight line that is roughly parallel to the Z2 axis direction. The lower end of the 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 of the spindle 60.

A rough grinding wheel 64 is attached to the underside of the mount 62 of the grinding unit 56 on the rough grinding area B side. 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 whose outer diameter is approximately equal to the diameter of the mount 62. In addition, both the inner and outer diameters of the rough grinding wheel 64 are longer than the radius of the workpiece 15.

On the underside of the rough grinding wheel base, multiple grinding wheels for rough grinding are arranged in a dispersed manner, each of which has rough grinding abrasive grains such as diamond suitable for rough grinding fixed with a bond such as vitrified or resinoid. In addition, the spindle housing 58 of the grinding unit 56 on the rough grinding area B side contains a rough grinding rotation drive source (not shown) such as a motor connected to the upper end side of the spindle 60.

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

In addition, a liquid supply nozzle (not shown) is provided near the rough grinding wheel 64 to supply 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 surfaces (grinding surfaces) of the multiple rough grinding grinding wheels. However, instead of or together with this liquid supply nozzle, a liquid supply port used to supply liquid may be provided on the rough grinding wheel 64.

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

On the underside of the finish grinding wheel base, multiple grinding wheels for finish grinding are arranged in a dispersed manner, each made of finish grinding abrasive grains such as diamond suitable for finish grinding (e.g., abrasive grains with an average grain size finer than that of coarse grinding abrasive grains) fixed with a bond such as vitrified or resinoid. In addition, the spindle housing 58 of the grinding unit 56 on the finish grinding area C side contains a rotational drive source for finish grinding such as a motor (not shown) connected to the upper end side of the spindle 60.

When the finish grinding rotary drive source operates, the finish grinding wheel 66 rotates together with the spindle 60. At this time, the multiple finish grinding grindstones included in the finish grinding wheel 66 trace an annular trajectory whose outer and inner diameters are both longer than the radius of the workpiece 15. In addition, this trajectory overlaps with the center of the holding surface 40a of the chuck table 40 positioned in the finish grinding area C.

In addition, a liquid supply nozzle (not shown) is provided next to the finish grinding wheel 66, which can supply 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 surfaces (grinding surfaces) of the multiple finish grinding grinding wheels. However, instead of or together with this liquid supply nozzle, a liquid supply port used to supply liquid may be provided on the finish grinding wheel 66.

The workpiece 15 held on the chuck table 40 is ground in sequence by the two grinding units 56 described above. Specifically, the workpiece 15 is ground in the rough grinding area B by the grinding unit 56 on the rough grinding area B side, and then in the finish grinding area C by the grinding unit 56 on the finish grinding area C side.

Furthermore, a transport mechanism 68 is provided in front of the loading/unloading area A and to the side of the transport mechanism 36, for transporting the workpiece 15 after grinding. Also, in front of the transport mechanism 68, a cleaning unit 70 is provided for cleaning the workpiece 15 transported from the chuck table 40 by the transport mechanism 68.

This cleaning unit 70 includes, for example, a spinner table that rotates while holding the front surface 15a side of the workpiece 15, and a nozzle that sprays a cleaning fluid onto the back surface (surface to be ground) 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, for example, into a cassette 30b.

Furthermore, the grinding device 24 may include components other than those described above. For example, the grinding device 24 may include a touch panel that includes a touch sensor that inputs instructions from an operator to the grinding device 24 and a display that outputs various information to the operator. The components of the grinding device 24 described above are connected to a control unit (not shown).

The 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 operation of the components of the grinding device 24 described above. For example, the control unit controls the components described above so that the workpiece 15 held on the chuck table 40 changes from its original thickness to its finished thickness.

Figures 8(A) and 8(B) are each a partial cross-sectional side view that shows a schematic diagram of grinding the back surface 15b side of the workpiece 15 using the grinding device 24. During this grinding, the transport mechanism 28 first transports the workpiece 15 out of the cassette 30a and onto the top surface of the disk-shaped table of the position adjustment mechanism 34 so that the back surface 15b of the workpiece 15 faces upward. As a result, the workpiece 15 is supported on the table via the protective tape 19 attached to its front surface 15a.

Then, by moving multiple pins arranged around the table in the radial direction of the table, the center of the workpiece 15 is positioned at a specific coordinate on the X2Y2 coordinate plane. Next, the transport mechanism 36 transports the workpiece 15 from the table of the position adjustment mechanism 34 and transports it onto the holding surface 40a of the chuck table 40 positioned in the load/unload area A. As a result, the workpiece 15 is supported on the chuck table 40 via the protective tape 19.

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

In addition, as the spindle 60 rotates, the mount 62 and the grinding wheel 64 for rough grinding rotate in the circumferential direction of the grinding wheel 64 for rough grinding (wheel base 64a for rough grinding). Next, while the chuck table 40 and the grinding wheel 64 for rough grinding are kept rotating, the grinding unit 56 on the rough grinding area B side is lowered so that the lower surfaces (grinding surfaces) of the multiple grinding stones 64b for rough grinding come into contact with the back surface 15b of the workpiece 15 (see FIG. 8 (A)).

As a result, the back surface 15b of the workpiece 15 is ground and removed by the lower sides of the multiple rough grinding grinding wheels 64b. This grinding (rough grinding) is continued until the thickness of the workpiece 15 reaches a predetermined thickness that is thicker than the finished thickness. For example, rough grinding is continued until the depth of the grooves 17 formed on the back surface 15b of the workpiece 15 is reduced to 1/3 to 1/10 times its original depth.

Next, the rotation of both the chuck table 40 positioned in the rough grinding area B and the spindle 60 of the grinding unit 56 on the rough grinding area B side is stopped, and the grinding unit 56 is raised. Next, the turntable 38 is rotated so that the chuck table 40 holding the workpiece 15 is positioned in the finish grinding area C. Next, both the chuck table 40 positioned in the finish grinding area C and the spindle 60 of the grinding unit 56 on the finish grinding area C side are rotated.

In addition, as the spindle 60 rotates, the mount 62 and the grinding wheel 66 for finish grinding rotate in the circumferential direction of the grinding wheel 66 for finish grinding (finish grinding wheel base 66a). Next, while the chuck table 40 and the grinding wheel 66 for finish grinding are kept rotating, the grinding unit 56 on the finish grinding area C side is lowered so that the lower surfaces (grinding surfaces) of the multiple grinding stones 66b for finish grinding come into contact with the back surface 15b of the workpiece 15 (see FIG. 8 (B)).

As a result, the back surface 15b of the workpiece 15 is ground and removed by the multiple finish grinding grinding wheels 66b. This grinding (finish grinding) is continued until the thickness of the workpiece 15 reaches the finish thickness. In other words, the grooves 17 formed on the back surface 15b of the workpiece 15 by the finish grinding disappear. As a result, the entire area of the workpiece 15 reaches the finish thickness.

In the above-mentioned method for grinding the workpiece, an annular groove 17 is formed on the back surface 15b of the workpiece 15, and then the back surface 15b of the workpiece 15 is ground. In this case, the back surface 15b of the workpiece 15 is ground while the areas near the bottom of the side surfaces of the multiple grinding wheels (the grinding wheel 64b for rough grinding and the grinding wheel 66b for finish grinding) collide with the areas near the top of the side surfaces of the groove 17 formed on the back surface 15b of the workpiece 15.

When such a collision occurs, the binder on the underside of the workpiece 15 becomes more likely to be scraped off. As a result, in the above-described method for grinding a workpiece, it is possible to promote the self-sharpening of each of the multiple grinding wheels (rough grinding grinding wheel 64b and finish grinding grinding wheel 66b) without weakening the holding force of the binder that holds the abrasive grains (rough grinding grains and finish grinding grains).

The above is one aspect of the present invention, and inventions having features different from those described above are also included in the present invention. For example, in the groove formation 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.

Each of Figures 9(A) and 9(B) is a partial cross-sectional side view that shows a schematic diagram of a grinding device being used to form a groove on the back surface (surface to be ground) 15b of a workpiece 15. The grinding device 72 shown in each of Figures 9(A) and 9(B) has a chuck table 74. This chuck table 74 has a disk-shaped frame made of, for example, ceramics or the like.

A recess with a circular opening at the top end is formed on the top surface of the frame, and a disk-shaped porous plate made of ceramics or the like is fixed in the recess. The top surface of the chuck table 74 is configured in a shape equivalent to the side of a cone whose center protrudes slightly beyond the outer edge, and functions as a holding surface 74a that holds the front surface 15a of the workpiece 15.

Specifically, the holding surface 74a is connected to a suction source (not shown) such as a vacuum pump via a suction passage (not shown) formed inside the chuck table 74. When the 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.

The chuck table 74 is connected to a chuck table moving mechanism (not shown) and can move horizontally. A grinding unit 76 is provided above the chuck table 74. The grinding unit 76 has a spindle 78 that can rotate around a rotation axis that is roughly parallel to the vertical direction.

A disk-shaped mount 80 is fixed to the lower end of the spindle 78. A groove-forming grinding wheel 82 is attached to the underside of the mount 80. The groove-forming grinding wheel 82 is made of a metal material such as stainless steel or aluminum, and has an annular groove-forming wheel base 82a whose outer diameter is roughly equal to the diameter of the mount 80.

In addition, both the inner and outer diameters of the groove forming grinding wheel 82 are longer than the radius of the workpiece 15 and shorter than the diameter of the workpiece 15. A plurality of groove forming grinding stones 82b, each made of groove forming abrasive grains such as diamonds fixed with a bond such as vitrified or resinoid, are arranged in a discrete manner on the underside of the groove forming wheel base 82a.

In addition, if 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 groove forming grinding wheel 82 may be the same as this grinding wheel (e.g., rough grinding wheel 64).

The upper end of the spindle 78 is connected to a rotary drive source (not shown) such as a motor. When the rotary drive source operates, the groove forming grinding wheel 82 rotates together with the spindle 78. At this time, the groove forming grinding stones 82b included in the groove forming grinding wheel 82 trace an annular trajectory whose outer and inner diameters are both longer than the radius of the workpiece 15 and shorter than the diameter of the workpiece 15.

In addition, a liquid supply nozzle (not shown) is provided next to the groove forming grinding wheel 82, which can supply 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 multiple groove forming grinding wheels 82b. However, instead of or together with this liquid supply nozzle, a liquid supply port used to supply liquid may be provided on the groove forming grinding wheel 82.

When using the grinding device 72 to form a groove on the back surface (grinding surface) 15b of the workpiece 15, first, the workpiece 15 is transported to the chuck table 74 so that the center of the workpiece 15 overlaps with the center of the chuck table 74 via the protective tape 19 attached to the front surface 15a.

Then, the chuck table 74 is operated so as 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 is 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.

Next, while rotating the chuck table 74 and the groove forming grinding wheel 82, the grinding unit 76 is lowered so that the lower surfaces (grinding surfaces) of the multiple groove forming grinding wheels 82b come into contact with the back surface (grinding surface) 15b of the workpiece 15. As a result, the annular area on the back surface 15b side of the workpiece 15 is ground and removed by the lower sides of the multiple groove forming grinding wheels 82b.

This grinding is continued until the distance between the bottom surfaces of the multiple groove forming grinding wheels 82b and the surface 15a of the workpiece 15 reaches a predetermined length that is thicker than the predetermined thickness that is longer 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)). As a result, an annular groove 21 is formed on the back surface 15b of the workpiece 15, concentric with the workpiece 15 and shallower than the difference between the original thickness and the finished thickness of the workpiece 15.

The groove forming step and grinding step of the present invention may also be performed in a single grinding device in which the relative positional relationship between the grinding unit and the chuck table can be changed as desired. Specifically, in this grinding device, the grinding unit and/or the chuck table are connected to a ball screw-type horizontal movement mechanism.

By operating this horizontal movement mechanism, the grinding unit and the chuck table can be moved relative to each other so as to switch between a state in which the straight line that is the rotation axis of the grinding wheel passes through the center of the holding surface of the chuck table and a state in which the trajectory of the rotating grinding wheel overlaps with the center of the holding surface of the chuck table.

In addition, the structures and methods of the above-described embodiments can be modified as appropriate without departing from the scope of the present invention.

2: Cutting device 4: Base 6: Cassette table 8: Cassette 10: Cover (10a: side, 10b: top)
11: Frame unit 12: Cutting unit 13: Dicing tape 14: Chuck table 15: Workpiece (15a: front surface, 15b: back surface (surface to be ground))
16: Touch panel 17: Groove 18: Warning light (pilot lamp)
19: Protective tape 20: Cutting blade 21: Groove 22: Spindle (spindle for cutting blade)
24: Grinding device 26: Base (26a: opening)
28: Transport mechanism 30a, 30b: Cassette 32a, 32b: Cassette placement table 34: Position adjustment mechanism 36: Transport mechanism 38: Turntable 40: Chuck table (40a: holding surface)
42: Support structure 44: Z2-axis movement mechanism 46: Guide rail 48: Movement plate 50: Screw shaft 52: Motor 54: Fixture 56: Grinding unit 58: Spindle housing 60: Spindle (grinding wheel spindle)
62: Mount 64: Grinding wheel for rough grinding
(64a: wheel base for rough grinding, 64b: grinding wheel for rough grinding)
66: Grinding wheel for finish grinding
(66a: wheel base for finish grinding, 66b: grinding wheel for finish grinding)
68: Transport mechanism 70: Cleaning unit 72: Grinding device 74: Chuck table (74a: holding surface)
76: Grinding unit 78: Spindle 80: Mount 82: Grinding wheel for forming groove
(82a: groove forming wheel base, 82b: groove forming grinding wheel)

Claims (4)

a groove forming step of forming an annular groove on a grinding surface of a disk-shaped workpiece, the groove being concentric with the disk-shaped workpiece and having a depth shallower than the difference between an original thickness and a finished thickness of the workpiece;
a grinding step in which, after the groove forming step, the workpiece and an annular grinding wheel having a plurality of grinding stones arranged in a discrete manner and an outer diameter longer than the radius of the workpiece are both rotated, and the grinding surfaces of the plurality of grinding stones are brought into contact with the grinding surface of the workpiece, thereby grinding the grinding surface side of the workpiece so that the entire area of the workpiece has the finishing thickness;
A method for grinding a workpiece, comprising: The grinding step includes:
a rough grinding step of grinding the grinding surface side of the workpiece using an annular rough grinding grinding wheel having a plurality of grinding stones for rough grinding each including abrasive grains for rough grinding arranged in a discrete manner;
a finish grinding step of grinding the grinding surface side of the workpiece to the finish thickness using an annular grinding wheel for finish grinding in which a plurality of grinding stones for finish grinding, each of which contains abrasive grains for finish grinding, are arranged in a discrete manner, so that the workpiece has the finish thickness;
2. The method for grinding a workpiece according to claim 1, further comprising the steps of: The groove forming step includes:
a cutting step of cutting the annular cutting blade into the grinding surface of the workpiece along a direction perpendicular to the grinding surface of the workpiece while the annular cutting blade is rotating;
a rotating step of rotating the workpiece at least once in a circumferential direction of the workpiece while the cutting blade is rotating after the cutting step;
3. The method for grinding a workpiece according to claim 1, further comprising the steps of: 3. The method for grinding a workpiece as described in claim 1 or 2, characterized in that the groove forming step is carried out by contacting the grinding surfaces of each of the plurality of groove forming grinding wheels with the grinding surface of the workpiece while both the workpiece and a circular groove forming grinding wheel having a plurality of groove forming grinding wheels arranged discretely and an outer diameter longer than the radius of the workpiece and shorter than the diameter of the workpiece are rotating.

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