JP2024060805A - Chuck table, grinding device, and holding surface forming method - Google Patents

Abstract

A warped wafer is ground to have a uniform thickness.
[Solution] Air is supplied to an elastic tube 20 provided between a central suction section 17 which holds the central portion of a wafer 100 and an outer peripheral holding section 18 which holds the outer peripheral portion, so that its upper end is brought into contact with the underside 100b of the wafer 100 whose outer periphery has been warped, the upper side 100a of the wafer 100 is ground with a grinding wheel 57 to weaken the force causing the wafer 100 to warp upward, the air is discharged from the elastic tube 20, the underside 100b of the wafer 100 is held by a central holding surface 21 and an outer peripheral holding surface 22 to grind the upper side 100a of the wafer 100, air is supplied to the elastic tube 20, so that the elastic tube 20 is brought into contact with the underside 100b of the wafer 100 held by suction to the central holding surface 21 and the outer peripheral holding surface 22, and the upper side 100a of the wafer 100 is ground with the grinding wheel 57 to make the wafer 100 have a predetermined thickness.
[Selected figure] Figure 5

Description

The present invention relates to a chuck table that holds a wafer by suction, a grinding device equipped with a chuck table, and a method for forming the holding surface of the chuck table.

For example, the following Patent Documents 1 and 2 propose a chuck table for holding a wafer with an element in which the outer periphery is warped upward from the center, which has a suction surface that sucks in the central portion of the underside of the wafer, and a ring-shaped elastic member that is placed on the outside of the suction surface and comes into contact with the underside of the outer periphery of the wafer.

JP 2016-031979 A JP 2018-207033 A

When the wafer held on the chuck table is ground with a grinding wheel, the grinding load crushes the elastic member that is in contact with the outer periphery of the underside of the wafer. This causes a problem in that the ground wafer has a thickened annular shape at the part that was in contact with the elastic member.

Therefore, when grinding a warped wafer, there is a challenge in forming the wafer to a uniform thickness.

The first invention is a chuck table which suction-holds the underside of a wafer in order to grind the upper surface of a wafer having an element in which the outer periphery is warped upward from the central portion with a grinding wheel, the chuck table comprising a central suction section which suction-holds the central portion of the underside of the wafer with a central holding surface, a peripheral suction section which suction-holds the peripheral portion of the underside of the wafer with a peripheral holding surface which is flush with the central holding surface, an annular elastic tube which fits into an annular groove formed between the central suction section and the peripheral suction section, and a frame having a recess which accommodates the central suction section, the annular groove and the peripheral suction section, the upper surface of the recess being flush with the peripheral holding surface, the frame comprising a central suction path which connects the central suction section to a suction source, a peripheral suction path which connects the peripheral suction section to the suction source, and an air supply path which connects the elastic tube to an air source.
A second invention is a grinding device comprising the chuck table of claim 1 for suction-holding the underside of a wafer having an element that causes the outer periphery to be warped up more than the central portion, a grinding mechanism for grinding the upper surface of the wafer held by suction on the chuck table with a grinding wheel, a thickness gauge for measuring the thickness of the wafer, and a control unit, the device further comprising a shape adjustment mechanism for changing the shape of the elastic tube by supplying air into the inside of the elastic tube to change the height of the upper end of the elastic tube in the vertical direction of the central holding surface, and the control unit controls the shape adjustment mechanism to supply air into the inside of the elastic tube to adjust the central holding surface of the wafer having a warped outer periphery that is held by suction on the central holding surface. a first control unit that brings the upper end of the elastic tube into contact with the underside of the wafer outside the portion held by the central holding surface; a second control unit that grinds the upper surface of the wafer with the grinding wheel to weaken the force causing the outer peripheral portion of the wafer to warp upward; a third control unit that uses the shape adjustment mechanism to exhaust air from inside the elastic tube and suck and hold the underside of the outer peripheral side of the wafer held by the central holding surface with the outer peripheral holding surface; and a fourth control unit that supplies air to the inside of the elastic tube with the shape adjustment mechanism to bring the elastic tube into contact with the underside of the wafer held by suction on the central holding surface and the outer peripheral holding surface, and grinds the upper surface of the wafer with the grinding wheel to grind the entire surface of the wafer to a predetermined thickness.
The grinding device may include a peripheral nozzle that supplies water to the peripheral portion of the wafer, and the second control unit may cause the peripheral nozzle to supply water to the peripheral holding surface.
A third invention is a holding surface forming method for forming the holding surface of the chuck table mounted on the grinding device, comprising: a grindstone mounting step for mounting a holding surface grinding wheel for grinding the upper surface of the chuck table to the grinding mechanism; a pressure adjustment step for adjusting the air pressure inside the elastic tube by the shape adjustment mechanism using an upper surface height measuring device for measuring the height of the upper surface of the chuck table so that the upper surface of the elastic tube is flush with the central holding surface or the outer peripheral holding surface; and a holding surface grinding step for grinding the central holding surface, the upper surface of the elastic tube, and the outer peripheral holding surface using the holding surface grinding wheel while maintaining the pressure value adjusted in the pressure adjustment step.

The chuck table of the present invention has an elastic tube fitted in the annular groove between the central suction portion and the outer periphery suction portion, so that the elastic tube is brought into contact with the underside of the wafer with its outer periphery warped, thereby making it possible to suck and hold the wafer without air leaking at least in the central suction portion. Also, by adjusting the height position of the upper end of the elastic tube, the thickness distribution (vertical cross-sectional shape) of the wafer being ground can be adjusted.
In the grinding device of the present invention, an elastic tube is fitted into the annular groove between the central suction part that suction-holds the central part of the wafer and the peripheral suction part that suction-holds the peripheral part, so that the upper end of the elastic tube is brought into contact with the lower surface of the wafer to grind the upper surface of the wafer, thereby weakening the warpage of the wafer, and then the upper end of the elastic tube is lowered to suction-hold the lower surface of the wafer on the central holding surface and the peripheral holding surface to grind the upper surface, thereby making the wafer thickness uniform. Therefore, it is no longer necessary to carry out the complicated work of grinding the wafer on a chuck table whose outer periphery is made of an elastic member to weaken the warpage, and then transferring the wafer to a chuck table without an elastic member to perform grinding, thereby making it possible to shorten the grinding time.

FIG. 1 is a perspective view showing an example of a grinding device. FIG. 2 is a perspective view showing an example of a chuck table and a base. FIG. 2 is a vertical cross-sectional view showing an example of a chuck table. 11 is a cross-sectional view showing a state in which the holding surface of the chuck table is self-ground; FIG. 1 is a cross-sectional view showing a state in which a wafer with a warped outer periphery side is held in a grinding device; 10 is a cross-sectional view showing a state in which a wafer is ground by bringing an upper end of an elastic tube into contact with a lower surface of the wafer whose outer periphery is warped upward. FIG. 11 is a cross-sectional view showing a state in which the upper end of the elastic tube is lowered to grind a wafer. FIG. 1 is a cross-sectional view showing a state in which a wafer is ground to have a uniform thickness;

The grinding device 1 shown in FIG. 1 includes a chuck table 10 that holds a wafer 100, a grinding mechanism 50 that grinds the wafer 100 held on the chuck table 10, a grinding feed mechanism 60 that moves the grinding mechanism 50 toward or away from the chuck table 10, a horizontal movement mechanism 70 that moves the chuck table 10 in the horizontal direction, and a thickness gauge 80 that measures the thickness of the wafer 100.

As shown in FIG. 2, the chuck table 10 includes a frame 11 having a recess 12 and a suction member 16 housed in the recess 12.

The frame 11 has a peripheral portion 14 formed one step lower than the upper surface 13, and the peripheral portion 14 has a plurality of through holes 15 formed at predetermined intervals in the circumferential direction, penetrating in the thickness direction.

The suction member 16 includes a central suction section 17 that suction-holds the central portion of the wafer 100, a peripheral suction section 18 that suction-holds the peripheral portion of the wafer 100, an annular groove 19 formed between the central suction section 17 and the peripheral suction section 18, and an annular elastic tube 20 fitted into the annular groove 19. The upper surface of the central suction section 17 constitutes a central holding surface 21 that suction-holds the central portion of the lower surface of the wafer, and the upper surface of the peripheral suction section 18 constitutes a peripheral holding surface 22 that suction-holds the peripheral portion of the lower surface 100b of the wafer 100.

The chuck table 10 is fixed to a base 30 shown in FIG. 2. The base 30 is formed to have the same diameter as the chuck table 10, and a number of screw holes 31 corresponding to the through holes 15 formed in the frame body 11 are formed on the periphery. The chuck table 10 is fixed to the base 30 by screwing a screw (not shown) inserted through the through hole 15 of the frame body 11 into the screw hole 31.

The base 30 has an annular central suction groove 32 formed at a position corresponding to the central suction portion 17 of the chuck table 10. A central suction passage 33 opens into the bottom surface of the central suction groove 32.
An air supply passage 34 opens at a position on the outer periphery of the central suction groove 32 corresponding to the annular groove 19 in which the elastic tube 20 of the chuck table 10 is housed.
An annular outer periphery suction groove 35 is formed on the outer periphery side of the air supply passage 34. The outer periphery suction groove 35 is formed at a position corresponding to the outer periphery suction portion 18 of the chuck table 10. An outer periphery suction passage 36 opens into the bottom surface of the outer periphery suction groove 35.

As shown in FIG. 3, the central holding surface 21 and the outer peripheral holding surface 22 are formed as a cone surface with the apex at the center of the chuck table 10. An air space 23 into which air is injected is formed inside the elastic tube 20, and the air space 23 communicates with an air supply passage 24 formed in the frame 11, and the air supply passage 24 opens at an air supply port 25 on the underside of the frame 11.

The frame 11 has a central suction passage 26 that communicates with the central suction section 17 of the chuck table 10. The central suction passage 26 opens at a central suction port 27 on the underside of the frame 11.

The frame 11 is formed with an outer periphery suction passage 28 that communicates with the outer periphery suction section 18 of the chuck table 10. The outer periphery suction passage 28 opens at an outer periphery suction port 29 on the underside of the frame 11.

As shown in FIG. 4, when the chuck table 10 is fixed to the base 30, the central suction port 27 of the frame 11 is connected to the central suction passage 33 of the base 30, the peripheral suction port 29 of the frame 11 is connected to the peripheral suction passage 36 of the base 30, and the air supply port 25 of the frame 11 is connected to the air supply passage 34 of the base 30.

The central suction passage 33 is connected to a suction source 39 via a central suction pipe 37 and an on-off valve 38. A pressure gauge 40 is connected to the central suction pipe 37.
The outer circumferential suction flow passage 36 is connected to a suction source 39 via an outer circumferential suction pipe 41 and an on-off valve 42. A pressure gauge 43 is connected to the outer circumferential suction pipe 41.
The air supply flow path 34 is connected to an air source 47 via an air supply pipe 44, a pressure regulating valve 45, and an on-off valve 46. By sending air from the air source 47 to the air space 23 of the elastic tube 20 via the pressure regulating valve 45 and the on-off valve 46, or by releasing air from the on-off valve 46, the shape of the elastic tube 20 can be changed to change the height of the upper surface of the elastic tube 20 in the direction perpendicular to the central holding surface 21. Therefore, the pressure regulating valve 45, the on-off valve 46, and the air source 47 constitute a shape adjustment mechanism 48.

As shown in FIG. 1, the grinding mechanism 50 includes a spindle 51 extending in the Z-axis direction, a spindle housing 52 that rotatably supports the spindle 51, a motor 53 that drives the spindle 51 to rotate, a mount 54 connected to the lower end of the spindle 51, and a grinding wheel 55 attached to the mount 54. The grinding wheel 55 is composed of a base 56 fixed to the mount 54 and a plurality of grinding stones 57 fixed in an annular shape to the lower surface of the base 56. When the motor 53 rotates the spindle 51, the grinding wheel 55 also rotates.

The grinding feed mechanism 60 includes a ball screw 61 extending in the Z-axis direction, a pair of guide rails 62 arranged parallel to the ball screw 61, a motor 63 that rotates the ball screw 61 forward and backward, a lift plate 64 that has a nut that screws onto the ball screw 61 and whose rear side (+Y side) is in sliding contact with the guide rail 62, and a holder 65 that is connected to the lift plate 64 and supports the spindle housing 52. When the motor 763 rotates the ball screw 61 forward and backward, the lift plate 64 rises and falls, and the grinding mechanism 50 rises and falls.

The base 30 to which the chuck table 10 shown in FIG. 2 is fixed is connected to the rotation drive mechanism 49 shown in FIG. 1 and is rotatable. Also, as shown in FIG. 1, the rotation drive mechanism 49 is fixed to a slide plate 74.

The horizontal movement mechanism 70 includes a ball screw 71 extending in the Y-axis direction, a pair of guide rails 72 arranged parallel to the ball screw 71, a motor 73 that rotates the ball screw 71 forward and reverse, and a slide plate 74 that has a nut that screws onto the ball screw 71 and whose lower side (-Z side) is in sliding contact with the guide rail 72. When the motor 73 rotates the ball screw 71 forward and reverse, the slide plate 74 slides in the Y-axis direction, and the chuck table 10 and the rotation drive mechanism 49 move in the Y-axis direction together with the slide plate 74.

The periphery of the chuck table 10 is covered by a cover 75, and a bellows 76 is connected to the +Y side and the -Y side of the cover 75. When the slide plate 74 is moved in the Y-axis direction by the horizontal movement mechanism 70, the rotation drive mechanism 49, the base 30, and the chuck table 10 also move in the Y-axis direction.

A thickness gauge 80 for measuring the thickness of the wafer 100 is disposed to the side of the movement path of the chuck table 10 in the Y-axis direction. The thickness gauge 80 includes a top surface height gauge 81 for measuring the height of the top surface 100a of the wafer 100, and a holding surface height gauge 82 for measuring the height of the central holding surface 21 and the peripheral holding surface 22 formed flush with the top surface 13 through measuring the height of the top surface 13 of the frame 11, and the thickness of the wafer 100 is found by calculating the difference between the measurement value of the top surface height gauge 81 and the measurement value of the holding surface height gauge 82.

1. Self-Grinding When grinding the upper surface 100a of the wafer 100, self-grinding is performed on the central holding surface 21, the outer peripheral holding surface 22 and the elastic tube 20 of the chuck table 10 beforehand.
This self-grinding is performed with air being supplied to the elastic tube 20, and after self-grinding, the central holding surface 21, the outer peripheral holding surface 22 and the upper surface of the elastic tube 20 become flush.

1, the grinding wheel 55 is mounted on the mount 54. Here, the grinding wheel constituting the grinding wheel 55 is a holding surface grinding wheel for grinding the central holding surface 21 and the outer peripheral holding surface 22 of the chuck table 10. Although not shown, for example, a through hole is formed in the mount 54, and a screw hole is formed in the base 56 of the grinding wheel 55, and the grinding wheel 55 is fixed to the mount 54 by inserting a screw (not shown) from above the mount 54 and screwing it into the screw hole in the base 56.

(2) Pressure Adjustment Step Next, the chuck table 10 is positioned to the side of the thickness gauge 80 by driving the horizontal movement mechanism 70, and the tip of the top surface height gauge 81 is brought into contact with the top surface of the elastic tube 20, while the tip of the holding surface height gauge 82 is brought into contact with, for example, the outer peripheral holding surface 22. Then, while measuring the height of the top surface of the elastic tube 20, the control unit 90 opens the on-off valve 46 shown in Fig. 4 to communicate the air source 47 with the air space 23 of the elastic tube 20, and controls the pressure adjustment valve 45 to adjust the air pressure inside the air space 23 so that the top surface of the elastic tube 20 is flush with the outer peripheral holding surface 22. Then, when the top surface of the elastic tube 20 and the outer peripheral holding surface 22 become flush with each other, the pressure adjustment valve 45 maintains the pressure at that time. In addition, the tip of the top surface height measuring device 81 may be brought into contact with the central holding surface 21 and the tip of the holding surface height measuring device 82 may be brought into contact with the top surface of the elastic tube 20, and the air pressure inside the air space 23 may be adjusted so that the top surface of the elastic tube 20 is flush with the top surface of the central holding surface 21.

1 rotates the chuck table 10, the motor 53 of the grinding mechanism 50 rotates the spindle 51, and the motor 63 of the grinding feed mechanism 60 rotates the ball screw 61 to lower the grinding mechanism 50 with the grinding wheel 55 rotating, and grinding is performed by bringing the rotating grinding wheel 57 into contact with the central holding surface 21, the peripheral holding surface 22 of the chuck table 10, and the upper surface of the elastic tube 20. As a result, the central holding surface 21, the peripheral holding surface 22, and the elastic tube 20 become flush with each other.

2. Grinding of the Wafer As shown in Fig. 5, the lower surface 100b of the wafer 100 is placed on the central holding surface 21, the outer peripheral holding surface 22, and the upper end of the elastic tube 20, which have been made flush by self-grinding. Then, the control unit 90 opens the on-off valve 38 to connect the central suction unit 17 to the suction source 39. Because the outer peripheral side of the wafer 100 is warped upward, there is a gap between the outer peripheral part of the central holding surface 21 and the lower surface 100b of the wafer 100, and suction force leaks from the central holding surface 21.

Therefore, under the control of the first control unit 91, the on-off valve 46 constituting the shape adjustment mechanism 48 is opened to supply air to the air space 23 of the elastic tube 20, thereby raising the upper end of the elastic tube 20 and bringing it into contact with the lower surface 100b of the wafer 100. Since the upper end of the elastic tube 20 comes into contact with the lower surface 100b of the wafer 100 outside the central holding surface 21, air leakage from the central holding surface 21 is eliminated. Therefore, the wafer 100 is held more stably than before the upper end of the elastic tube 20 came into contact with the lower surface 100b of the wafer 100.
In this manner, since the outer periphery of the wafer 100 is warped upward, the central portion of the lower surface of the wafer 100 is suction-held only by the central holding surface 21 .
Alternatively, the negative pressure on the central holding surface 21 may be monitored to recognize that the upper end of the elastic tube 20 has come into contact with the lower surface 100b of the wafer 100. In other words, the negative pressure value on the central holding surface 21 increases in the negative direction to recognize that the elastic tube 20 has come into contact with the lower surface 100b of the wafer 100.
Then, the air pressure in the air space 23 of the elastic tube 20 may be gradually reduced, and the wafer 100 may be forcibly held by the suction force of the central holding surface 21. In other words, the air pressure in the air space 23 of the elastic tube 20 may be gradually reduced until the negative pressure value of the central holding surface 21 begins to change in the positive direction, and the entire surface of the central holding surface 21 may be brought closer to the lower surface 100b of the wafer 100.

From this state, as shown in FIG. 6, under the control of the second control unit 92, the rotary drive mechanism 49 is driven to rotate the chuck table 10, the motor 53 constituting the grinding mechanism 50 is driven to rotate the grinding wheel 55, and the motor 63 constituting the grinding feed mechanism 60 is driven to lower the grinding mechanism 50. Then, the grinding wheel 57 comes into contact with the outer periphery of the upper surface 100a of the wafer 100, and the upper surface 100a is ground while pressing down on the wafer 100 from above and weakening the warping force. Because more of the outer periphery of the upper surface 100a of the wafer 100 is ground, the wafer 100 is formed with a thinner outer periphery.

Alternatively, an outer periphery nozzle 83 may be provided outside the outer periphery suction unit 18, and water supplied from a water source 84 may be sprayed from the outer periphery nozzle 83 toward the gap between the outer periphery holding surface 22 and the lower surface 100b of the wafer 100 under the control of the second control unit 92. This forms a water seal at the contact portion between the upper end of the elastic tube 20 and the lower surface of the wafer 100, preventing air leakage from the central holding surface 21 and further stabilizing the holding state of the wafer 100. It is also possible to prevent grinding debris from entering the gap and adhesion of grinding debris to the outer periphery holding surface 22.
Alternatively, the outer periphery suction section 18 may be connected to the suction source 39, water may be supplied from the outer periphery nozzle 83, and the upper surface 100a of the wafer 100 may be ground while the water is sucked from the outer periphery suction surface.

In this way, grinding is continued with leakage from the central holding surface 21 prevented, and under the control of the third control unit 93, the pressure adjustment valve 45 constituting the shape adjustment mechanism 48 is used to exhaust air from the air space 23 of the elastic tube 20, the peripheral holding surface 22 is connected to a suction source, and the height of the upper end of the elastic tube 20 is adjusted to the height of the central holding surface 21, as shown in Fig. 7, so that the lower surface 100b of the wafer 100 is suction-held by the central holding surface 21 and the peripheral holding surface 22. As a result, the lower surface 100b of the wafer 100 is suction-held following the central holding surface 21 and the peripheral holding surface 22.
When discharging the air from the air space 23 of the elastic tube 20 , water may be supplied from the outer peripheral nozzle 83 to the outer peripheral holding surface 22 .

In addition, a nozzle 85 may be provided that sprays water downward from above the outer periphery of the wafer 100, and under the control of the third control unit 93, as shown in FIG. 7, water supplied from a water source 84 to the nozzle 85 may be sprayed toward the outer periphery holding surface 22 to press the outer periphery of the wafer 100 downward, and the lower surface 100b of the wafer 100 may be held by suction to the outer periphery holding surface 22.

Next, under the control of the fourth control unit 94, the pressure adjustment valve 45 constituting the shape adjustment mechanism 48 is adjusted to supply air to the air space 23 of the elastic tube 20, and the upper end of the elastic tube 20 is brought into contact with the lower surface 100b of the wafer 100 held by suction on the central holding surface 21 and the outer peripheral holding surface 22 as shown in Fig. 8, and the lower surface 100b of the wafer 100 is supported by the central holding surface 21, the outer peripheral holding surface 22 and the upper end of the elastic tube 20 so that the wafer 100 does not become annularly recessed at the annular contact portion, and the upper surface 100a of the wafer 100 is ground by the grinding wheel 57. Then, when the thickness of the wafer 100 measured by the thickness gauge 80 reaches a predetermined thickness, the grinding feed mechanism 60 raises the grinding mechanism 50 to finish grinding.
Although the thickness gauge 80 measures the thickness of the wafer 100 at the portion held by the central holding surface 21, a thickness gauge may be added to measure the thickness of the portion held by the peripheral holding surface 22. Using the added thickness gauge, for example, under the control of the second control unit 92, only the thickness of the peripheral portion of the wafer 100 held by the peripheral holding surface 22 is measured, and a change in the thickness is judged to indicate that the force of warping has weakened, under the control of the third control unit 93, it is judged that the peripheral holding surface 22 has suction-held the lower surface of the wafer 100 because the height of the upper surface of the peripheral portion of the wafer 100 held by the peripheral holding surface 22 has dropped, and under the control of the fourth control unit 94, the thicknesses of two locations, the thickness of the portion held by the central holding surface 21 and the thickness of the portion held by the peripheral holding surface 22, may be measured. In other words, grinding may be performed until the values of the two thickness gauges match and a predetermined thickness is obtained.
In addition, when the thickness of the portion held by the outer peripheral holding surface 22 is smaller than a preset finishing thickness, the processing may be terminated without performing grinding by the fourth control unit 94.
In addition, under the control of the third control unit 93, whether or not the outer peripheral holding surface 22 is holding the lower surface 100b of the wafer 100 by suction may be determined by monitoring the negative pressure value (suction force) of the outer peripheral holding surface 22 and determining based on the negative pressure value.
Furthermore, under the control of the second control unit 92, the on-off valve 42 is opened to connect the outer periphery suction unit 18 to the suction source 39, while water is supplied from the outer periphery nozzle 83 to the outer periphery holding surface 22 to grind the outer periphery portion of the wafer 100. When the outer periphery portion of the wafer 100 is ground and the height of its upper surface decreases, and the thickness of the outer periphery portion of the wafer 100 becomes smaller than the thickness of the central portion of the wafer 100, it may be determined under the control of the third control unit 93 that the outer periphery holding surface 22 has suction-held the underside 100b of the wafer 100.

During grinding under the control of the fourth control unit 94, the underside 100b of the wafer 100 is suction-held by the central holding surface 21 and the outer peripheral holding surface 22, and between the central holding surface 21 and the outer peripheral holding surface 22, the upper end of the elastic tube 20 is in contact with the underside 100b of the wafer 100 so as not to lift the wafer 100, thereby allowing the wafer 100 to be formed to a uniform thickness.
In addition, instead of the elastic tube 20, a ring-shaped elastic member and a lifting mechanism for raising and lowering the ring-shaped elastic member may be provided, and the upper end of the elastic member may be brought into contact with the underside of the wafer 100 held by suction by the central holding surface 21 and the peripheral holding surface 22.

As described above, in the grinding device 1, the elastic tube 20 is fitted into the annular groove 19 between the central suction section 17 that suction-holds the central part of the wafer 100 and the peripheral suction section 18 that suction-holds the peripheral part, so that the elastic tube 20 is brought into contact with the lower surface 100b of the wafer 100 whose outer periphery is warped, and the grinding wheel 57 presses and grinds the outer periphery of the wafer 100, thereby weakening the warping of the wafer 100. Then, the upper end of the elastic tube 20 is lowered to suction-hold the lower surface 100b of the wafer 100 on the central holding surface 21 and the peripheral holding surface 22, and the upper surface 100a is ground, thereby making the thickness of the wafer 100 uniform. Therefore, it is no longer necessary to perform the cumbersome work of grinding the wafer 100 on a chuck table whose outer periphery is made of an elastic material to weaken the warping, and then transferring the wafer 100 to a chuck table without an elastic material for grinding, thereby shortening the grinding time.

1: Grinding device, 10: Chuck table, 11: Frame, 12: Recess, 13: Upper surface, 14: Periphery,
15: through hole, 16: suction member, 17: central suction portion, 18: outer peripheral suction portion, 19: annular groove,
20: Elastic tube, 21: Central support surface, 22: Outer peripheral support surface, 23: Air space,
24: air supply passage, 25: air supply port, 26: central suction passage, 27: central suction port,
28: outer periphery suction passage, 29: outer periphery suction port, 30: base, 31: screw hole, 32: central suction groove,
33: central suction passage, 34: air supply passage, 35: outer circumferential suction groove, 36: outer circumferential suction passage,
37: central suction pipe, 38: on-off valve, 39: suction source, 40: pressure gauge, 41: outer circumferential suction pipe,
42: on-off valve, 42: on-off valve, 43: pressure gauge, 44: air supply pipe,
45: pressure regulating valve, 46: opening/closing valve, 47: air source, 48: shape adjusting mechanism,
49: Rotation drive mechanism, 50: Grinding mechanism, 51: Spindle,
52: spindle housing, 53: motor, 54: mount, 55: grinding wheel,
56: base, 57: grinding wheel, 60: grinding feed mechanism, 61: ball screw,
62: guide rail, 63: motor, 64: lift plate, 65: holder,
70: horizontal movement mechanism, 71: ball screw, 72: guide rail, 73: motor,
74: Slide plate, 75: Cover, 76: Bellows, 80: Thickness measuring device, 81: Top surface height measuring device, 82: Holding surface height measuring device,
83: outer peripheral nozzle, 83: nozzle, 84: water source, 85: nozzle 90: control unit, 91: first control unit, 92: second control unit, 93: third control unit,
94: Fourth control unit 100: Wafer, 100a: Upper surface, 100b: Lower surface

Claims (4)

A chuck table that holds the bottom surface of a wafer by suction in order to grind the top surface of the wafer, the top surface of which has an element that causes the outer periphery to be warped upward from the center portion, with a grinding wheel,
the central suction section sucks and holds the central portion of the lower surface of the wafer with a central holding surface, a peripheral suction section sucks and holds the peripheral portion of the lower surface of the wafer with a peripheral holding surface that is flush with the central holding surface, an annular elastic tube that fits into an annular groove formed between the central suction section and the peripheral suction section, and a frame having a recess that houses the central suction section, the annular groove, and the peripheral suction section, the upper surface of the recess being flush with the peripheral holding surface,
the frame body includes a central suction passage that connects the central suction portion to a suction source, an outer peripheral suction passage that connects the outer peripheral suction portion to a suction source, and an air supply passage that connects the elastic tube to an air source.
Chuck table. 13. A grinding apparatus comprising: a chuck table according to claim 1 for suction-holding a bottom surface of a wafer having an element in which an outer periphery is warped upward more than a central portion; a grinding mechanism for grinding an upper surface of the wafer held by suction on the chuck table with a grinding wheel; a thickness gauge for measuring a thickness of the wafer; and a control unit,
a shape adjusting mechanism for changing the shape of the elastic tube by supplying air into the elastic tube to change the height of the upper end of the elastic tube in a vertical direction to the central holding surface;
The control unit
a first control unit that supplies air into the elastic tube by the shape adjustment mechanism to bring an upper end of the elastic tube into contact with a lower surface of the wafer that is held by the central holding surface and has a curved outer periphery, the lower surface being located outside a portion held by the central holding surface;
a second control unit that grinds the upper surface of the wafer with the grinding wheel to reduce a force that causes an outer peripheral portion of the wafer to warp upward;
a third control unit that uses the shape adjustment mechanism to exhaust air from inside the elastic tube and suck and hold, with the outer peripheral holding surface, the lower surface of the outer peripheral side of the wafer that is held with the central holding surface;
a fourth control unit that supplies air into the elastic tube by the shape adjustment mechanism to bring the elastic tube into contact with the lower surface of the wafer held by suction on the central holding surface and the outer circumferential holding surface, and grinds the upper surface of the wafer with the grinding wheel to grind the entire surface of the wafer to a predetermined thickness;
A grinding device comprising: a peripheral nozzle for supplying water to a peripheral portion of the wafer;
3. The grinding apparatus according to claim 2, wherein the second control section supplies water to the outer periphery holding surface from the outer periphery nozzle. 3. A method for forming the holding surface of the chuck table mounted on the grinding apparatus according to claim 2, comprising the steps of:
a grindstone mounting step of mounting a holding surface grinding stone to the grinding mechanism for grinding the upper surface of the chuck table;
a pressure adjusting step of adjusting the air pressure inside the elastic tube by the shape adjusting mechanism using an upper surface height measuring device that measures the height of the upper surface of the chuck table so that the upper surface of the elastic tube is flush with the central holding surface or the outer peripheral holding surface;
a holding surface grinding step of grinding the central holding surface, the upper surface of the elastic tube, and the outer peripheral holding surface using the holding surface grinding wheel while maintaining the pressure value adjusted in the pressure adjusting step;
A method for forming a support surface comprising:

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