JP2021136333A - Grinding method - Google Patents

Abstract

To reduce the amount of grinding dust attached to an external part of a holding surface and an external part of a protective member.SOLUTION: A grinding method of grinding a back surface side of a processed material having a device region and an outer periphery excessive region surrounding the circumference of the device region on a front surface side, comprises: a front surface protective step of covering the front surface side of the processed material with a protective member; a holding step of sucking and holding the front surface side of the processed material via the protective member with a chuck table having a holding surface of which a diameter is larger than a diameter of the device region and smaller than an outer diameter of the processed material; and a grinding step of forming a disc-like concave part structured by: a circular ground part that rotates the chuck table in the circumference of a first rotational axis, and contacts a grinding whetstone to one part of the back surface side while supplying a grinding water to the grinding whetstone in a state where a grinding wheel is rotated in the circumference of a second rotational axis to grind one part of the back surface side, and to which the grinding is executed; and a ring-like reinforcement part which surrounds the circumference of the ground part and to which the grinding is not executed.SELECTED DRAWING: Figure 2

Description

The present invention includes a circular portion to be ground that has been ground by grinding a part of the back surface side of the workpiece, and a ring-shaped reinforcing portion that surrounds the portion to be ground and has not been ground. The present invention relates to a grinding method for forming a disk-shaped recess composed of, on the back surface side of a work piece.

A work piece in which a plurality of scheduled division lines intersecting each other are set on the surface side, and devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are formed in each area partitioned by the plurality of scheduled division lines. It is divided into a plurality of device chips through grinding, cutting, etc.

For example, after grinding the entire back surface side of the disk-shaped workpiece using a grinding device to thin it to a predetermined thickness, the workpiece is cut along each scheduled division line using a cutting device. The work piece is divided into a plurality of device chips.

Before grinding the work piece, a disk-shaped sheet (protective member) made of resin is attached to the surface side of the work piece. The protective member has a base material layer and a glue layer provided on the first surface of the base material layer. After the first surface side is attached to the workpiece, the second surface (held surface) side located on the side opposite to the first surface is sucked and held by a chuck table mounted on the grinding device.

The chuck table has a disk-shaped frame made of ceramics. A disk-shaped recess is formed in the frame body, and a disk-shaped porous plate is fixed to the recess. The upper surface of the porous plate is substantially flat and forms substantially flush with the annular upper surface of the frame body located outside the recess.

One end of the flow path is connected to the lower surface of the porous plate, and a suction source such as a vacuum pump is connected to the other end of the flow path. The negative pressure generated by the suction source acts on the upper surface of the porous plate via the flow path.

The upper surface of the porous plate and the annular upper surface of the frame form a holding surface that sucks and holds the surface side (that is, the held surface side of the protective member) of the workpiece. In a grinding machine, a holding surface having a diameter larger than the outer diameter of the work piece is usually taken into consideration, such as the tolerance of the outer diameter of the work piece and the misalignment when the work piece is placed on the holding surface. A chuck table equipped with is used.

At the time of grinding, an annular grinding wheel is used to grind the entire back surface side of the workpiece while supplying grinding water such as pure water to the machining point. At this time, the used grinding water containing machining debris flows from the outer peripheral portion on the back surface side of the workpiece to the outer peripheral portion of the holding surface, and is further held with the held surface of the protective member by the suction force of the porous plate. Infiltrate between the surface. Therefore, grinding debris adheres to the outer peripheral portion of the held surface of the protective member and the outer peripheral portion of the holding surface.

By the way, there is known a method of grinding a part of the back surface side (that is, a circular region) corresponding to a device region, not the entire back surface side of the workpiece (see, for example, Patent Document 1). By leaving a ring-shaped reinforcing portion that is not ground so as to surround the circular region (that is, the portion to be ground) that has been ground, it becomes easy to handle the work piece after grinding.

Even when the back surface side is ground so as to leave the ring-shaped reinforcing portion, as described above, after attaching the protective member to the front surface side, it has a holding surface having a diameter larger than the outer diameter of the workpiece. The chuck table sucks and holds the surface side of the work piece.

Therefore, the grinding debris adheres to the outer peripheral portion of the holding surface and the outer peripheral portion of the held surface of the protective member. If the state in which the grinding debris adheres to the outer peripheral portion of the holding surface is left unattended, the grinding apparatus becomes dirty. In addition, dirt adheres to the apparatus used in the process following grinding through the workpiece to which dirt such as grinding dust has adhered.

Further, if the workpiece is processed while dirt such as grinding chips is attached to the holding surface, the stress may be concentrated at the position where the grinding chips are attached and the workpiece may be cracked. In addition, the suction force on the holding surface may decrease due to grinding debris or the like, resulting in poor grinding. In addition, when the work piece is sucked and conveyed by the suction device, suction failure may occur due to grinding debris or the like, and the work piece may fall and crack.

Japanese Unexamined Patent Publication No. 2007-19461

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the amount of grinding debris adhering to the outer peripheral portion of the holding surface and the outer peripheral portion of the held surface of the protective member.

According to one aspect of the present invention, a grinding wheel having a grinding wheel is used on the back surface side of a workpiece having a device region on which a plurality of devices are formed and an outer peripheral surplus region surrounding the device region on the front surface side. A method for grinding a work piece to be ground, which is a surface protection step in which the surface side of the work piece is covered with a protective member, and a diameter larger than the diameter of the device region and smaller than the outer diameter of the work piece. A holding step of sucking and holding the surface side of the workpiece through the protective member and the chuck table being rotated around a first rotation axis and holding the chuck table. In a state where the grinding wheel is rotated around the second rotation axis, the grinding grindstone is brought into contact with a part of the back surface side while supplying grinding water to the grinding grindstone, so that a part of the back surface side is formed. A grinding step that grinds to form a disk-shaped recess composed of a circular ground portion that has been ground and a ring-shaped reinforcing portion that surrounds the ground portion and has not been ground. And, a grinding method comprising.

In the grinding step according to one aspect of the present invention, the grinding wheel is brought into contact with a part of the back surface side to grind a part of the back surface side instead of the entire back surface side to form a circular portion to be ground. .. That is, a ring-shaped reinforcing portion that surrounds the portion to be ground and is not ground is left.

As described above, since there is a portion that is not ground in the grinding step, it is not necessary to suck and hold the entire surface side of the workpiece. The present application focuses on this point, and in the holding step, a chuck table having a holding surface having a diameter larger than the diameter of the device region and smaller than the outer diameter of the work piece is used to hold the surface side of the work piece. Suction and hold.

Therefore, in the grinding step, the used grinding water containing the machining chips falls or scatters downward from the outer peripheral portion on the back surface side of the workpiece. As a result, it becomes difficult for the used grinding water to get around the outer peripheral portion of the holding surface and the outer peripheral portion of the held surface of the protective member. Therefore, it is possible to reduce the amount of grinding debris that wraps around and adheres to the outer peripheral portion of the holding surface and the outer peripheral portion of the held surface of the protective member.

It is a perspective view which shows the surface protection step. FIG. 2A is a partial cross-sectional side view showing the grinding step, and FIG. 2B is a partially enlarged view of FIG. 2A. FIG. 3A is a perspective view of the workpiece unit after the grinding step, and FIG. 3B is a cross-sectional view of the workpiece unit after the grinding step. It is a flow chart of a grinding method. 5 (A) is a partial cross-sectional side view showing a grinding step according to a comparative example, FIG. 5 (B) is a top view of a holding surface after grinding according to a comparative example, and FIG. 5 (C) is a comparison. It is a bottom view of the work piece unit after grinding which concerns on an example.

An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. First, the workpiece 11 and the like to be ground will be described with reference to FIG. The workpiece 11 is, for example, a disk-shaped wafer made of a semiconductor material such as silicon.

The surface 11a side of the workpiece 11 is divided into a plurality of regions by a plurality of scheduled division lines (streets) 13 intersecting each other, and devices 15 such as ICs and LSIs are formed in each region.

There are no restrictions on the material, shape, structure, size, etc. of the workpiece 11. For example, a substrate made of a semiconductor material other than silicon can be used as the workpiece 11. Similarly, there are no restrictions on the type, quantity, shape, structure, size, arrangement, etc. of the device 15.

On the surface 11a side of the workpiece 11, a circular device region 17a including a plurality of devices 15 and an annular outer peripheral surplus region 17b surrounding the device region 17a and not provided with the device 15 are provided. There is.

In FIG. 1, the boundary line between the device area 17a and the outer peripheral surplus area 17b is shown by a broken line, but this boundary line is a virtual line and is not actually attached to the workpiece 11. Bevel portions (see FIG. 2A and the like) having chamfered corners are formed on the outer peripheral portions of the workpiece 11 on the front surface 11a side and the back surface 11b side.

Next, a method of grinding the back surface 11b side of the workpiece 11 to form a disk-shaped recess on the back surface 11b side will be described with reference to FIGS. 1 to 4. FIG. 4 is a flow chart of a grinding method according to an embodiment of the present invention.

First, in order to protect the surface 11a side, a protective member 19 is attached to the surface 11a side of the workpiece 11, to form a workpiece unit 21 whose surface 11a side is covered with the protective member 19 (surface protection step). (S10)).

FIG. 1 is a perspective view showing a surface protection step (S10). The protective member 19 is attached so as to cover the bevel portion on the surface 11a side in addition to the surface 11a. The protective member 19 is a disk-shaped sheet made of resin, and has a base material layer and a glue layer provided on the first surface of the base material layer.

The glue layer is made of, for example, an ultraviolet curable resin, but may be made of a thermosetting resin or a naturally curable resin. The base material layer does not necessarily have to be provided with a glue layer. For example, the protective member 19 may be composed of only the base material layer and may be attached to the surface 11a side by an alternative method such as thermocompression bonding.

After the front surface protection step (S10), the back surface 11b side is ground using the grinding device 20. The grinding device 20 includes a chuck table 22. The chuck table 22 has a disk-shaped frame body 24 made of ceramics.

A disk-shaped recess 24a is formed in the frame body 24, and a disk-shaped porous plate 26 is fixed to the recess 24a. One end of a predetermined flow path (not shown) is connected to the lower surface side of the porous plate 26. A suction source (not shown) such as a vacuum pump is connected to the other end of the flow path. The negative pressure generated by the suction source acts on the upper surface 26a of the porous plate 26 via the flow path.

The upper surface 26a is substantially flat and forms substantially flush with the annular upper surface 24b of the frame body 24 located outside the recess 24a. The upper surface 26a of the porous plate 26 and the upper surface 24b of the frame body 24 form a holding surface 28 that attracts and holds the surface 11a side of the workpiece 11.

The holding surface 28 of the present embodiment has a diameter larger than the diameter of the device region 17a and smaller than the outer diameter of the workpiece 11. An output shaft (first rotation shaft) 30 of a rotation drive source (not shown) such as a motor is fixed to the lower portion of the frame body 24.

The output shaft 30 is arranged along the Z-axis direction (grinding feed direction) so as to be substantially orthogonal to the holding surface 28. A grinding unit 32 is arranged above the chuck table 22. The grinding unit 32 has a cylindrical spindle housing (not shown) arranged in the height direction along the Z-axis direction.

A ball screw type grinding feed mechanism (not shown) for moving the spindle housing along the Z-axis direction is connected to the spindle housing. Inside the spindle housing, a part of a columnar spindle (second rotating shaft) 34 is supported in a rotatable manner.

The spindle 34 is arranged so as to be substantially parallel to the output shaft 30 of the chuck table 22. A rotary drive source such as a motor is connected to the upper end of the spindle 34, and a disk-shaped wheel mount 36 is fixed to the lower end of the spindle 34.

An annular grinding wheel 38 is mounted on the lower surface of the wheel mount 36. The grinding wheel 38 has an annular wheel base 38a. On one surface side of the wheel base 38a, a plurality of block-shaped grinding wheels 38b are discretely arranged at substantially equal intervals along the circumferential direction of the wheel base 38a.

When the plurality of grinding wheels 38b rotate around the spindle 34, an annular region is formed by the locus of movement of the plurality of grinding wheels 38b. In the present embodiment, the diameter of the outermost circumference of the annular region is set to be larger than the radius of the device region 17a and smaller than the diameter of the device region 17a.

After the surface protection step (S10), the center position of the front surface 11a (or the back surface 11b) is adjusted using an alignment device (not shown). After that, the workpiece 11 is placed on the holding surface 28 so that the center of the front surface 11a (or the back surface 11b) and the center of the holding surface 28 substantially coincide with each other.

Next, as shown in FIG. 2, the surface 11a side of the workpiece unit 21 (that is, the holding surface side of the protective member 19) is suction-held by the holding surface 28 (holding step (S20)). As described above, the diameter of the holding surface 28 is equal to or larger than the outer diameter of the device region 17a and equal to or smaller than the outer diameter of the workpiece 11.

Therefore, at least a part of the outer peripheral excess region 17b is located outside the holding surface 28. In this state, the chuck table 22 is rotated around the output shaft 30 at the first rotation speed, and the grinding wheel 38 is further rotated around the spindle 34 at the second rotation speed, for example, in the same direction as the output shaft 30. Rotate.

In addition, the grinding wheel 38 is grounded and fed while supplying the grinding water 40 such as pure water to the grinding wheel 38b from the grinding water supply port (not shown) provided on the grinding wheel 38. Then, the grinding wheel 38b is brought into contact with the region on the back surface 11b side corresponding to the device region 17a (grinding step (S30)).

FIG. 2A is a partial cross-sectional side view showing the grinding step (S30), and FIG. 2B is a partially enlarged view of FIG. 2A. In the grinding step (S30), a part of the back surface 11b side corresponding to the device region 17a is ground to form a circular portion to be ground 11c.

In the grinding step (S30), the used grinding water 40 containing the machining chips falls or scatters downward from the outer peripheral portion on the back surface 11b side of the workpiece 11, so that the outer peripheral portion of the holding surface 28 and the protective member 19 It becomes difficult for the used grinding water 40 to wrap around the outer peripheral portion. Therefore, the amount of grinding debris adhering to the outer peripheral portion of the holding surface 28 and the protective member 19 can be reduced.

In addition, by setting the diameter of the holding surface 28 to be equal to or larger than the outer diameter of the device region 17a, it is possible to grind the region on the back surface 11b side corresponding to the device region 17a while appropriately supporting the device region 17a. Grinding defects in the portion 11c can be avoided.

FIG. 3A is a perspective view of the workpiece unit 21 after the grinding step (S30), and FIG. 3B is a cross-sectional view of the workpiece unit 21 after the grinding step (S30). A ring-shaped reinforcing portion 11d that has not been ground remains so as to surround the periphery of the portion 11c to be ground. The portion to be ground 11c and the ring-shaped reinforcing portion 11d form a disk-shaped recess 11e.

Next, a comparative example will be described with reference to FIGS. 5 (A) to 5 (C). The grinding device 50 according to the comparative example includes a chuck table 52. The chuck table 52 has a disk-shaped frame 54 made of ceramics.

A disk-shaped recess 54a is formed in the frame body 54. The recess 54a is provided with a disk-shaped porous plate 56 having an outer diameter smaller than the diameter of the recess 54a. Further, an annular barrier portion 58 having pores smaller than the pores of the porous plate 56 is provided between the outer circumference of the porous plate 56 and the inner circumference of the recess 54a.

One end of a predetermined flow path (not shown) is connected to the lower surface side of the porous plate 56 and the barrier portion 58. A suction source (not shown) such as a vacuum pump is connected to the other end of this flow path. The negative pressure generated by the suction source acts on the upper surface 26a of the porous plate 26 and the upper surface 58a of the barrier portion 58 via the flow path.

Since the barrier portion 58 has pores smaller than the pores of the porous plate 56, the magnitude of the negative pressure acting on the upper surface 58a of the barrier portion 58 is the negative pressure acting on the upper surface 26a of the porous plate 26. It is smaller than the size of.

The upper surface 56a and the upper surface 58a are substantially flat and form substantially flush with the annular upper surface 54b of the frame body 54 located outside the recess 54a. The upper surface 26a and the upper surface 58a and the upper surface 54b form a holding surface 60 that sucks and holds the surface 11a side of the workpiece 11.

The holding surface 60 has a diameter larger than the outer diameter of the workpiece 11. An output shaft 62 of a rotation drive source (not shown) such as a motor is fixed to the lower part of the frame body 54. The grinding unit 32, which is the same as that of the above-described embodiment, is arranged above the chuck table 52.

When a part of the back surface 11b side of the workpiece 11 is ground by using the grinding device 50 according to the comparative example, the surface protection step (S10) to the grinding step (S30) are sequentially performed in the same manner as in the above-described embodiment.

FIG. 5A is a partial cross-sectional side view showing the grinding step (S30) according to the comparative example. The workpiece 11 is suction-held by a holding surface 60 having a diameter larger than the outer diameter of the workpiece 11. In particular, the upper surface 58a of the barrier portion 58 has an exposed region that is not in contact with the protective member 19.

Therefore, in the grinding step (S30), the used grinding water 40 containing the machining chips passes from the back surface 11b side of the workpiece 11 through the bevel portion of the outer peripheral portion of the workpiece 11 and the holding surface 60. Flows to the outer periphery of. At this time, the used grinding water 40 penetrates between the held surface and the holding surface 60 of the protective member 19 by the suction force of the porous plate 56 and the barrier portion 58.

Therefore, grinding debris 64 (see FIGS. 5B and 5C) adheres to the outer peripheral portion of the holding surface 60 and the outer peripheral portion of the held surface of the protective member 19. FIG. 5B is a top view of the holding surface 60 after grinding according to the comparative example. As shown in FIG. 5B, after grinding, a large amount of grinding debris 64 is attached near the boundary between the upper surface 58a of the barrier portion 58 and the upper surface 56a of the porous plate 56.

Further, after grinding, a large amount of grinding debris 64 also adheres to the outer peripheral portion of the held surface of the protective member 19. FIG. 5C is a bottom view of the work piece unit 21 after grinding according to the comparative example. The broken line shown in FIG. 5C means the boundary between the upper surface 58a and the upper surface 56a.

As shown in the comparative examples of FIGS. 5A to 5C, when a chuck table 52 having a holding surface 60 having a diameter larger than the outer diameter of the workpiece 11 is used, it is after grinding. Adhesion of grinding debris 64 becomes a problem.

On the other hand, in the above-described embodiment, the amount of grinding debris 64 adhering to the outer peripheral portion of the holding surface 28 and the outer peripheral portion of the held surface of the protective member 19 can be reduced. In addition, the structure, method, and the like according to the above-described embodiment can be appropriately modified and implemented as long as they do not deviate from the scope of the object of the present invention.

11: Work piece, 11a: Front surface, 11b: Back surface, 11c: Grinded portion, 11d: Ring-shaped reinforcing portion, 11e: Recessed portion 13: Scheduled division line 15: Device 17a: Device region, 17b: Outer peripheral surplus region 19: Protective member 20: Grinding device 21: Work unit 22: Chuck table 24: Frame, 24a: Recess, 24b: Top surface 26: Porous plate, 26a: Top surface 28: Holding surface 30: Output shaft 32: Grinding unit 34: Spindle 36: Wheel mount 38: Grinding wheel, 38a: Wheel base, 38b: Grinding grindstone 40: Grinding water 50: Grinding device 52: Chuck table 54: Frame body, 54a: Recessed shape, 54b: Top surface 56: Porous plate, 56a : Top surface 58: Barrier portion, 58a: Top surface 60: Holding surface 62: Output shaft 64: Grinding waste

Claims (1)

A method of grinding a workpiece that has a device region on which a plurality of devices are formed and an outer peripheral surplus region surrounding the device region on the front surface side, and the back surface side of the workpiece is ground with a grinding wheel having a grinding wheel. There,
A surface protection step that covers the surface side of the work piece with a protective member,
A chuck table having a holding surface having a diameter larger than the diameter of the device region and smaller than the outer diameter of the work piece, and holding the work piece by sucking and holding the surface side of the work piece through the protective member. Steps and
With the chuck table rotated around the first axis of rotation and the grinding wheel rotated around the second axis of rotation, the grinding wheel was moved while supplying grinding water to the grinding wheel. A part of the back surface side is ground by contacting a part of the back surface side, and a circular ground portion to be ground and a ring shape surrounding the ground portion and not being ground. A grinding method comprising a reinforcing portion and a grinding step for forming a disk-shaped recess composed of the reinforcing portion.

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