JP7381254B2 - Wafer grinding method - Google Patents

Description

The present invention relates to a method for grinding a wafer.

A grinding device that grinds a wafer using a grinding wheel uses a height gauge to measure the height of the top surface of the wafer in order to recognize the height of the top surface of the wafer. The thickness of the wafer is calculated based on the amount of displacement of the upper surface of the wafer that is displaced due to the grinding process, and when the wafer thickness reaches a desired thickness, the grinding process is finished.

Height gauges include contact height gauges and non-contact height gauges. Non-contact height gauges include ultrasonic height gauges and optical measurement height gauges, but grinding water supplied during grinding interferes with measurement, making it difficult to accurately measure the height of the top surface of the wafer. Moreover, it becomes expensive to be able to measure accurately. Therefore, an inexpensive contact type height gauge as shown in Patent Document 1 is often used.

JP2009-113149

However, if the probe of the contact type height gauge is charged with static electricity, the static electricity may be discharged just before the probe contacts the wafer, and the discharge may damage the devices formed on the wafer. Therefore, there is a problem in preventing the contact type height gauge that measures the height of the top surface of the wafer from discharging static electricity.

The present invention provides a chuck table having a holding surface for holding a wafer, a grinding means having a grinding wheel for grinding the wafer held on the chuck table, and a probe for contacting the top surface of the wafer to raise the height of the top surface of the wafer. A height gauge for measuring the resistance value, a grinding water supply means for supplying pure water with a high resistance value as grinding water to the upper surface of the wafer, and a grinding water supply means for supplying the grinding water to the top surface of the wafer, and a grinding wheel used to grind the wafer while supplying the grinding water. A wafer is processed using a grinding device that includes a grinding waste liquid reservoir for collecting a grinding waste liquid containing conductive grinding debris, and a waste liquid supply means for supplying the grinding waste liquid stored in the grinding waste liquid reservoir to the probe. A method for grinding a wafer to be ground, the holding step of holding the wafer on the chuck table, and after the holding step, lowering the probe toward the wafer while supplying the grinding waste liquid to the probe, A top surface height measurement start step of bringing the probe into contact with the top surface of the wafer and starting measuring the height of the top surface of the wafer; and after stopping the supply of the grinding waste liquid, the grinding process is performed using the grinding water supply means. This wafer grinding method includes a grinding step of grinding the top surface of the wafer using the grinding wheel while supplying water until the height of the top surface of the wafer reaches a preset height.
The present invention provides a chuck table having a holding surface for holding a wafer, a grinding means having a grinding wheel for grinding the wafer held on the chuck table, and a probe for contacting the top surface of the wafer to raise the height of the top surface of the wafer. A wafer grinding method for grinding a wafer using a grinding device comprising a height gauge for measuring the resistance of the chuck, and a grinding water supply means for supplying pure water having a high resistance value as grinding water to the upper surface of the wafer. A holding step in which the wafer is held on a table; and after the holding step, while supplying the grinding water, the grinding wheel is brought into contact with the wafer to grind the upper surface of the wafer, thereby grinding the upper surface of the wafer containing conductive grinding debris. A probe contact preparation step in which the waste liquid is accumulated on the upper surface of the wafer, and the probe is lowered toward the upper surface of the wafer where the grinding waste liquid is accumulated, and the probe is brought into contact with the upper surface of the wafer. A top surface height measurement start step of starting measurement of the height, and a top surface height measurement step of starting height measurement, and measuring the height of the top surface of the wafer using the height gauge, which has the probe in contact with the top surface of the wafer, while supplying the grinding water using the grinding water supply means. This wafer grinding method includes a grinding step of grinding the upper surface of the wafer using the grinding wheel until the height reaches a preset height while measuring the height.

In the present invention, by supplying the grinding waste liquid to the first probe, static electricity is prevented from being discharged between the first probe and the wafer when the first contact of the first probe and the top surface of the wafer come into contact with each other. can be prevented.
Furthermore, by grinding the wafer while supplying grinding water, the grinding waste liquid containing conductive grinding debris is retained on the upper surface of the wafer, so that the first contact of the first probe and the upper surface of the wafer are in contact with each other. It is possible to prevent static electricity from discharging between the first probe and the wafer when they come into contact with each other. In order to supply the grinding waste liquid between the first contact of the first probe and the upper surface of the wafer, there is no need for a grinding waste liquid reservoir or waste liquid supply means, which reduces the time and economic costs required for grinding the wafer. can be reduced.

It is a perspective view showing the whole grinding device. FIG. 3 is a cross-sectional view of the chuck table seen from the side, showing how the grinding waste liquid is pumped out from the grinding waste liquid reservoir and supplied to the first probe. FIG. 2 is a cross-sectional view of a wafer being ground while a grinding waste liquid containing grinding debris is retained on the upper surface of the wafer, as seen from the side of the chuck table.

1 Grinding Apparatus The grinding apparatus 1 shown in FIG. 1 is a grinding apparatus that grinds the wafer W held on the holding surface 20a of the chuck table 2 using the grinding means 3. Note that the wafer W is a semiconductor wafer or the like. For example, a protection member S is attached to the lower surface Wb of the wafer W, and the wafer W and the protection member S form an integrated work unit U. The configuration of the grinding device 1 will be described below.

The grinding device 1 includes a base 10 extending in the Y-axis direction, and a column 11 erected on the +Y direction side of the base 10.

On the side surface of the column 11 in the -Y direction, a grinding feed means 4 that supports the grinding means 3 so as to be movable up and down is provided. The grinding means 3 includes a spindle 30 having a rotating shaft 35 in the Z-axis direction, a housing 31 that rotatably supports the spindle 30, a spindle motor 32 that rotationally drives the spindle 30 about the rotating shaft 35, and a spindle 30. The grinding wheel 34 includes an annular mount 33 connected to the lower end of the mount 33 and a grinding wheel 34 detachably attached to the lower surface of the mount 33.
The grinding wheel 34 includes a wheel base 341 and a plurality of approximately rectangular parallelepiped-shaped grinding wheels 340 arranged annularly on the lower surface of the wheel base 341, and the lower surface 340b of the grinding wheel 340 grinds the wafer W. It has a ground surface.

The grinding feed means 4 includes a ball screw 40 having a rotation axis 45 in the Z-axis direction, a pair of guide rails 41 arranged parallel to the ball screw 40, and a Z-axis that rotates the ball screw 40 about the rotation axis 45. It includes a shaft motor 42, an elevating plate 43 whose internal nut is screwed onto a ball screw 40 and whose side portion slides on a guide rail 41, and a holder 44 connected to the elevating plate 43 and supporting the grinding means 3.

When the ball screw 40 is driven by the Z-axis motor 42 and rotates around the rotating shaft 45, the elevating plate 43 is guided by the guide rail 41 and moves up and down in the Z-axis direction. This occurs when the grinding means 3 held by the holder 44 moves in a direction perpendicular to the holding surface 20a (Z-axis direction).

The grinding device 1 includes a scale unit 71. The scale unit 71 includes a scale 710 disposed on the side surface of the guide rail 41 in the -Y direction, and a reading section 711 disposed on the side surface of the elevating plate 43 in the +X direction and at a position adjacent to the scale 710. It is equipped with The reading unit 711 has, for example, an optical recognition mechanism that reads reflected light from the graduations formed on the scale 710, and can recognize the graduations of the scale 710.
For example, the height position of the reading unit 711 and the height position of the lower surface 340b of the grinding wheel 340 are correlated, and the height position of the lower surface 340b of the grinding wheel 340 is determined based on the height position of the reading unit 711. The structure is such that it can be measured.

A chuck table 2 is arranged on the base 10. The chuck table 2 includes a suction section 20 that includes, for example, a porous member, and a frame 21 that supports the suction section 20. The upper surface of the suction unit 20 is a holding surface 20a on which the wafer W is held, and the upper surface 21a of the frame 21 is formed flush with the holding surface 20a.

Further, the chuck table 2 is connected to a rotating means 24. The chuck table 2 can be rotated by the rotation means 24 about a rotation shaft 25 in the Z-axis direction.

Below the chuck table 2 inside the base 10, for example, a horizontal moving means (not shown) is provided. The chuck table 2 is movable in the Y-axis direction by horizontal moving means or the like.

A cover 12 and a bellows 13 extendably connected to the cover 12 are disposed around the chuck table 2. When the chuck table 2 moves in the Y-axis direction, the cover 12 moves integrally with the chuck table 2 in the Y-axis direction, and the bellows 13 expands and contracts.

The grinding device 1 is equipped with a thickness measuring means 5. The thickness measuring means 5 includes an upper surface height gauge 51 that measures the height of the upper surface Wa of the wafer W, a holding surface height gauge 52 that measures the height of the holding surface 20a, and a substantially cylindrical structure that supports the upper surface height gauge 51 and the holding surface height gauge 52. It is provided with a shaft portion 50 having a shape.
The top height gauge 51 includes a first probe 510 and a first support part 511 that is connected to the upper end of the first probe 510 and supports the first probe 510. At the lower end of the first probe 510, a first contact 510a that contacts the upper surface Wa of the wafer W, etc. is provided.
Similarly, the holding surface height gauge 52 includes a second probe 520 and a second support part 521 that is connected to the upper end of the second probe 520 and supports the second probe 520. A second contact 520a that contacts the upper surface 21a of the frame 21 is disposed at the lower end of the second probe 520.
By moving the first support part 511 and the second support part 521 in the vertical direction like a lever with their respective base sides as a fulcrum, the first contact 510a and the second support part 521 The contactor 520a moves up and down in the Z-axis direction.

By using the thickness measuring means 5 during the grinding process of the wafer W, the first contact 510a of the first probe 510 provided in the top surface height gauge 51 is brought into contact with the top surface Wa of the wafer W held on the holding surface 20a. The height of the upper surface Wa of the wafer W is measured, and the height of the holding surface 20a is measured by contacting the second contact 520a of the second probe 520 provided in the holding surface height gauge 52, and the difference in height between the two is measured. The thickness of the wafer W can be measured by calculating the value of .

As shown in FIG. 2, the grinding device 1 includes a grinding water supply means 6. The grinding water supply means 6 is connected to a water source 60, for example. Pure water with a large resistance value is stored in the water source 60, and the pure water supplied from the water source 60 to the grinding water supply means 6 is supplied from the grinding water supply means 6 to the upper surface Wa of the wafer W as grinding water. That will happen. Note that the grinding water supply means 6 may have a structure in which grinding water is ejected from the inside of the grinding wheel 340 through the inside of the spindle 30 that constitutes the grinding means 3.

The grinding device 1 also includes a grinding waste liquid reservoir section 8 . The grinding waste liquid reservoir 8 contains conductive grinding waste generated by grinding the wafer W using the grinding wheel 340 while supplying grinding water to the upper surface Wa of the wafer W using the grinding water supply means 6. It has a function of storing grinding waste liquid L.
Note that before the grinding process of the wafer W is performed, the grinding waste liquid L containing conductive grinding debris generated during the past grinding process is stored in the grinding waste liquid reservoir 8 in advance.
The grinding device 1 includes a waste liquid supply means 9. The waste liquid supply means 9 includes a pump 90 that pumps up the grinding waste liquid L stored in the grinding waste liquid reservoir 8 and a grinding waste liquid nozzle 91 that supplies the grinding waste liquid L pumped up by the pump 90 to the first probe 510. There is.

2 Wafer grinding method [First embodiment]
(holding process)
When grinding a wafer W using the above grinding apparatus 1, first, as shown in FIG. It is placed on the holding surface 20a of the chuck table 2 so that the holding surface 20a and the holding surface 20a are in contact with each other. Then, by suctioning the holding surface 20a from below using a suction means (not shown) or the like, the wafer W is suctioned and held on the holding surface 20a.

(Top surface height measurement start process)
With the wafer W being held on the holding surface 20a, the chuck table 2 is moved in the +Y direction using, for example, a horizontal movement means (not shown). As a result, the chuck table 2 moves horizontally and approaches the thickness measuring means 5, and the first probe 510 of the top height gauge 51 is positioned above the holding surface 20a of the chuck table 2, and the top surface 21a of the frame 21 is positioned above the holding surface 20a of the chuck table 2. The second probe 520 of the holding surface height gauge 52 is positioned above the holding surface height gauge 52 .
At this time, the chuck table 2 is positioned below the grinding wheel 340.

Next, while the waste liquid supply means 9 shown in FIG. By lowering the first probe 510 and bringing it into contact with the upper surface Wa of the wafer W, measurement of the height of the upper surface Wa of the wafer W is started.
When supplying the grinding waste liquid L to the first probe 510, specifically, the grinding waste liquid L stored in the grinding waste liquid reservoir 8 shown in FIG. It is then conveyed to the grinding waste liquid nozzle 91. Then, the grinding waste liquid L transported to the grinding waste liquid nozzle 91 is ejected from the grinding waste liquid nozzle 91 to the first probe 510 . As a result, the grinding waste liquid L is supplied to the first probe 510.

(Grinding process)
After the grinding waste liquid L is supplied to the first probe 510, the operation of the waste liquid supply means 9 is stopped, and the supply of the grinding waste liquid L to the first probe 510 is stopped. Then, the wafer W is ground using the grinding wheel 340 until the height of the upper surface Wa of the wafer W reaches a preset height.

In the grinding process of the wafer W, first, the chuck table 2 is rotated around the rotation shaft 25 using the rotation means 24, so that the wafer W, which is suctioned and held on the holding surface 20a, is rotated around the rotation shaft 25. Rotate around the axis.
Then, by rotating the spindle 30 around the rotating shaft 35 using the spindle motor 32 of the grinding means 3, the spindle 30 is connected to an annular mount 33 connected to the lower end of the spindle 30 and the mount 33. The grinding wheel 340 is similarly rotated about the rotating shaft 35.

When the Z-axis motor 42 of the grinding feed means 4 is used to drive the ball screw 40 to rotate the ball screw 40 around the rotating shaft 45 while the grinding wheel 340 is rotating, the elevating plate 43 and the elevating plate The grinding wheel 340 supported by the holder 43 descends in the -Z direction, and as shown in FIG. 2, the grinding surface 340a of the grinding wheel 340 comes into contact with the wafer W held on the holding surface 20a. . With the grinding surface 340a in contact with the wafer W, the grinding wheel 340 is further pushed down toward the wafer W to grind the wafer W.

At this time, using the grinding water supply means 6, pure water having a large resistance value is supplied as grinding water from the water source 60 to a position where the upper surface Wa of the wafer W and the lower surface 340b of the grinding wheel 340 are in contact with each other.
The grinding water supplied to the upper surface Wa of the wafer W and the lower surface 340b of the grinding wheel 340 mixes with conductive grinding debris generated by the grinding process of the wafer W, and becomes a grinding waste liquid L.
Here, the wafer W is rotating around a rotating shaft 25, and the grinding waste liquid L accumulated on the upper surface Wa of the wafer W is moved from the outer circumferential area of the wafer W to the outside in the radial direction of the wafer W under the influence of centrifugal force. The grinding waste liquid is scattered towards the ground and collected in the grinding waste liquid storage section 8. The grinding waste liquid L accumulated in the grinding waste liquid reservoir 8 is similarly jetted from the grinding waste liquid nozzle 91 to the first probe 510 before grinding another wafer.

Further, the first contact 510a of the first probe 510 of the top surface height gauge 51 is in contact with the top surface Wa of the wafer W, and the height of the top surface Wa of the wafer W is measured.
When the height of the upper surface Wa of the wafer W reaches a preset height, the grinding process of the wafer W is finished. Thereby, the wafer W is ground to a desired thickness.

In this grinding method, by supplying the grinding waste liquid L to the first probe 510, when the first contact 510a of the first probe 510 and the upper surface Wa of the wafer W come into contact, the first probe 510 and the wafer W This can prevent static electricity from discharging between the

For example, when grinding a plurality of wafers W in succession, as described above, after the grinding of the wafers W is finished, the wafers W that have been ground are separated from the chuck table 2, and, for example, The unprocessed wafer W is held on the holding surface 20a and ground using the grinding wheel 340. At that time, since there is no grinding waste liquid on the wafer W to be ground, the grinding waste liquid L is supplied to the first probe 510 to prevent electrostatic discharge between the first probe 510 and the wafer W. It is desirable to do so.

[Second embodiment]
(holding process)
First, as shown in FIG. 1, the wafer W is placed on the holding surface 20a of the chuck table 2 in the same way as the holding process in the first embodiment. Then, by suctioning the holding surface 20a from below using a suction means (not shown) or the like, the wafer W is suctioned and held on the holding surface 20a.

(Probe contact preparation process)
Next, as shown in FIG. 3, pure water having a high resistance value is supplied as grinding water from the water source 60 to a position where the upper surface Wa of the wafer W and the lower surface 340b of the grinding wheel 340 contact each other, using the grinding water supply means 6. Meanwhile, the grinding wheel 340 is brought into contact with the wafer W held on the holding surface 20a, and the upper surface Wa of the wafer W is ground.
The grinding water supplied to the upper surface Wa of the wafer W and the lower surface 340b of the grinding wheel 340 mixes with conductive grinding debris generated by the grinding process of the wafer W, and becomes grinding waste liquid L, which remains on the upper surface Wa of the wafer W. do.

(Top surface height measurement start process)
Thereafter, the first probe 510 of the top surface height gauge 51 is lowered toward the top surface Wa of the wafer W where the grinding waste liquid L has accumulated, and the first probe 510 is brought into contact with the top surface Wa of the wafer W. Measurement of the height of the upper surface Wa is started.

(Grinding process)
Thereafter, the wafer W is subjected to grinding processing in the same manner as in the first embodiment. Specifically, the chuck table 2 and the wafer W held on the holding surface 20a of the chuck table 2 are rotated about the rotation shaft 25 using the rotation means 24, and the wafer W is removed from the grinding water supply means 6. Grinding water is supplied to the position where the grinding wheel 340 and the grinding wheel 340 come into contact. Then, while measuring the height of the upper surface Wa of the wafer W using the upper surface height gauge 51, the wafer W is ground using the grinding wheel 340. The upper surface of the wafer W is ground using the grinding wheel 340 until the height of the upper surface Wa of the wafer W reaches a preset height.

In this grinding method, by grinding the wafer W while supplying grinding water, the grinding waste liquid L containing conductive grinding debris is retained on the upper surface Wa of the wafer W, and then the first Since the contactor 510a and the upper surface Wa of the wafer W are in contact with each other, static electricity can be prevented from discharging between the first probe 510 and the wafer W.
Further, according to the present grinding method, in order to supply the grinding waste liquid between the first contact 510a of the first probe 510 and the upper surface Wa of the wafer W, the grinding waste liquid reservoir 8 of the first embodiment or the waste liquid supply The means 9 and the like are not required, and the time and economic costs required for grinding the wafer W can be reduced.

1: Grinding device 10: Base 11: Column 12: Cover 13: Bellows 2: Chuck table 20: Suction part 20a: Holding surface 21: Frame 21a: Upper surface of frame 24: Rotating means 25: Rotating shaft 3: Grinding means 30: Spindle 31: Housing 32: Spindle motor 33: Mount 34: Grinding wheel 340: Grinding wheel 340b: Bottom surface of grinding wheel 341: Wheel base 35: Rotating shaft 4: Grinding feed means 40: Ball screw 41: Guide rail 42: Z-axis motor 43: Elevating plate 44: Holder 45: Rotating shaft 5: Thickness measuring means 50: Shaft portion 51: Top surface height gauge 510: First probe 510a: First contact 511: First support portion 52: Holding surface height gauge 520 : Second probe 520a: Second contact 521: Second support part 6: Grinding water supply means 60: Water source 71: Scale unit 710: Scale 711: Reading section 8: Grinding waste liquid reservoir 9: Waste liquid supply means 90: Pump 91: Grinding waste liquid nozzle L: Grinding waste liquid W: Wafer Wa: Upper surface of wafer Wb: Lower surface of wafer S: Protective member Sb: Lower surface of protective member U: Work unit

Claims (2)

a chuck table that holds a wafer on a holding surface; a grinding means that uses a grinding wheel to grind the wafer held on the chuck table; a probe that contacts the top surface of the wafer to be ground by the grinding wheel; A wafer grinding method for grinding a wafer using a grinding device comprising a height gauge for measuring the height of the wafer, and a grinding water supply means for supplying pure water as grinding water to the upper surface of the wafer, the grinding device comprising: a grinding waste liquid reservoir for supplying the grinding water and storing a grinding waste liquid containing conductive grinding debris generated by grinding a wafer using the grinding wheel; and a waste liquid supply means for supplying waste liquid to the probe,
a holding step of holding the wafer on the chuck table;
After the holding step, while supplying the grinding waste liquid to the probe, the probe is moved toward the wafer, and the probe is placed on the top surface of the wafer while preventing electrostatic discharge between the probe and the wafer. a top surface height measurement start step of bringing the wafer into contact and starting measuring the height of the top surface of the wafer;
Stopping the supply of the grinding waste liquid, and while supplying the grinding water using the grinding water supply means, use the grinding wheel until the height of the top surface of the wafer as measured by the height gauge reaches a preset height. a grinding process of grinding the top surface of the wafer;
A wafer grinding method comprising: a chuck table that holds a wafer on a holding surface; a grinding means that uses a grinding wheel to grind the wafer held on the chuck table; a probe that contacts the top surface of the wafer to be ground by the grinding wheel; A wafer grinding method for grinding a wafer using a grinding device comprising a height gauge for measuring the height of the wafer, and a grinding water supply means for supplying pure water as grinding water to the upper surface of the wafer, the method comprising:
a holding step of holding the wafer on the chuck table;
After the holding step, while supplying the grinding water, the grinding wheel is brought into contact with the wafer to grind the top surface of the wafer, and a probe contact preparation is performed in which the grinding waste liquid containing conductive grinding debris is retained on the top surface of the wafer. process and
The probe is moved toward the top surface of the wafer where the grinding waste liquid is accumulated to prevent static electricity from being discharged between the probe and the wafer, and the probe is brought into contact with the top surface of the wafer to remove the top surface of the wafer. a top surface height measurement start step of starting measurement of the height of the
While supplying the grinding water, the height of the top surface of the wafer is measured by the height gauge with the probe in contact with the top surface of the wafer, using the grinding wheel until the height reaches a preset height. A method for grinding a wafer, comprising: a grinding step of grinding the upper surface of the wafer.

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