JP7455470B2 - Wafer processing method - Google Patents

Description

The present invention relates to a wafer processing method used when grinding a wafer having protruding electrodes.

In order to reduce the size and weight of device chips that are incorporated into various electronic devices, there are increasing opportunities to thin wafers before they are divided into device chips. For example, the wafer can be ground and thinned by holding the front side of the wafer with devices on a chuck table and pressing a rotating grindstone tool against the back side of the wafer.

When grinding a wafer using the method described above, a protective tape made of a material such as resin is attached to the front surface of the wafer to protect the device from shocks applied during grinding. On the other hand, when a device is provided with protruding electrodes called bumps, a height difference occurs on the front surface side of the wafer between the device region where the protruding electrodes are present and the peripheral excess region surrounding the device region.

In such a situation, the peripheral excess area of the wafer cannot be properly held by the chuck table, so even if protective tape is applied to the front side of the wafer, there is a high probability that the wafer will be damaged when the load from the grinding tool is applied to the peripheral excess area. Therefore, a technology has been proposed in which protective tape with a glue layer (thick adhesive layer) that is thicker than the height of the protruding electrodes is applied to the front side of the wafer (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2013-21017

If the above-mentioned technique is used, the height difference on the front surface side caused by the protruding electrodes can be absorbed by the adhesive layer, and the entire front side of the wafer including the excess outer region can be appropriately held on the chuck table. However, in this technique, the protective tape is attached to the wafer so that the protruding electrodes are buried in the thick adhesive layer, so the glue (adhesive) gets into the gaps formed by the protruding electrodes.

As a result, when the protective tape is peeled off, adhesive remains on the wafer side, potentially resulting in poor connections between the protruding electrodes and the wiring. In addition, there was a risk that the glue remaining on the wafer side would deteriorate, reducing the reliability of the device.

The present invention has been made in view of these problems, and its purpose is to reduce the possibility of damage to the wafer and to remove the adhesive from the protective tape from remaining in the gaps caused by the protruding electrodes. An object of the present invention is to provide a wafer processing method that can grind wafers.

According to one aspect of the present invention, a device region in which a device having a plurality of protruding electrodes is formed in each of a plurality of regions partitioned by intersecting planned dividing lines, and a peripheral surplus region surrounding the device region. A wafer processing method used when processing a wafer including a front surface, a back surface opposite to the front surface, and a side surface connecting the outer peripheral surplus area of the front surface and the back surface, the method comprising: By supplying and curing a resin so as to partially or completely cover the outer circumferential excess area and the side surface of the surface, the resin has a thickness corresponding to the protruding electrode in a portion covering the outer circumferential excess area. a step of forming a resin member to form a member; a step of applying a protective tape to a portion of the resin member covering the excess outer peripheral region and the plurality of protruding electrodes after performing the step of forming the resin member; A method for processing a wafer is provided, comprising: after performing the step of applying a protective tape, holding the front side of the wafer on a holding table via the protective tape and the resin member, and grinding the back side of the wafer. be done. In the resin member forming step, the resin may be supplied to a mold attached to the wafer.

In the wafer processing method according to one embodiment of the present invention, a resin member is formed whose portion covering the excess outer circumferential area has a thickness corresponding to the protruding electrode, and then a protective tape is attached to the portion of the resin member that covers the excess outer circumferential area. Therefore, the front side of the wafer can be properly held on the holding table without using a protective tape having an adhesive layer that is thicker than the height of the protruding electrodes.

In other words, unlike the case where only a protective tape with a small (thin) adhesive layer is used without using a resin member, the difference in height on the front side of the wafer is sufficiently small, so that the excess area on the outer periphery is added during grinding. The possibility of wafer breakage due to loading is also reduced. Further, unlike when using a protective tape having an adhesive layer that is thicker than the height of the protruding electrodes, the adhesive of the protective tape does not remain in the gaps caused by the protruding electrodes.

Therefore, according to the wafer processing method according to one aspect of the present invention, it is possible to grind the wafer without leaving the adhesive of the protective tape in the gap caused by the protruding electrode while suppressing the possibility of the wafer being damaged.

FIG. 1(A) is a perspective view schematically showing a wafer, and FIG. 1(B) is a cross-sectional view schematically showing the wafer. FIG. 2(A) is a perspective view schematically showing how a mold is attached to a wafer, and FIG. 2(B) is a cross-sectional view schematically showing a state where a die is attached to a wafer. be. FIG. 3 is a cross-sectional view schematically showing how a resin member is formed to cover the peripheral excess area and side surface of the front surface of the wafer. FIG. 4 is a cross-sectional view schematically showing a state in which the mold is removed from the wafer and the resin member. FIG. 5 is a cross-sectional view schematically showing a state in which a protective tape is attached to a resin member. FIG. 6 is a side view schematically showing how the back surface of the wafer is ground.

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1(A) is a perspective view schematically showing a wafer 11 processed by the wafer processing method according to the present embodiment, and FIG. 1(B) is a cross-sectional view schematically showing the wafer 11. . As shown in FIGS. 1A and 1B, the wafer 11 is formed into a disk shape using a semiconductor such as silicon, and has a generally flat surface 11a and a side opposite to the surface 11a. , and a side surface 11c connecting the front surface 11a and the back surface 11b.

The front surface 11a side of the wafer 11 is divided into a device region including a central portion and an outer peripheral surplus region surrounding the device region, and a side surface 11c connects this peripheral surplus region and the back surface 11b. The device area is further divided into a plurality of small areas by a plurality of dividing lines (street) 13 that intersect with each other, and a device 15 such as an IC (Integrated Circuit) is formed in each small area. Each device 15 has a plurality of protruding electrodes (bumps) 15a each made of a solder ball or the like.

Note that, in this embodiment, a disk-shaped wafer 11 formed using a semiconductor such as silicon is illustrated, but there are no restrictions on the material, shape, structure, size, etc. of the wafer 11. For example, a substrate made of other materials such as semiconductors, ceramics, resins, metals, etc. can also be used as the wafer 11. Similarly, there are no restrictions on the type, quantity, shape, structure, size, arrangement, etc. of the device 15.

In the wafer processing method according to this embodiment, a resin member is formed to cover a part of the wafer 11 (resin member forming step). Specifically, first, a mold necessary for forming the resin member is mounted on the wafer 11. 2(A) is a perspective view schematically showing how the mold 21 is attached to the wafer 11, and FIG. 2(B) is a perspective view schematically showing the state where the die 21 is attached to the wafer 11. FIG.

As shown in FIGS. 2(A) and 2(B), the mold 21 has a disk-shaped bottom portion 21a having a larger diameter than the wafer 11, and is connected to the outer periphery of the upper surface side of the bottom portion 21a. and a cylindrical side portion 21b having a height greater than or equal to the height. The upper surface of the bottom portion 21a is formed generally flat. Further, on the upper surface of the bottom portion 21a, an annular partition portion 21c is provided that can partition the device region of the wafer 11 from the peripheral surplus region.

The height of the partition portion 21c (the distance between the top surface of the bottom portion 21a and the apex of the partition portion 21c) is, for example, the same as or slightly larger than the distance from the surface 11a of the wafer 11 to the apex of the protruding electrode 15a, or Slightly smaller. That is, the partition portion 21c is formed at a height corresponding to the protruding electrode 15a. Such a mold 21 is obtained, for example, by machining a metal plate, typically stainless steel, using a method such as CNC machining or electric discharge machining.

When mounting the mold 21 on the wafer 11, as shown in FIG. The wafer 11 is accommodated in the space inside the mold 21. As a result, as shown in FIG. 2B, the space inside the mold 21 is divided into a circular (disc-shaped) space A in a top view that accommodates the device region of the wafer 11 and a space A that accommodates the device region of the wafer 11, as shown in FIG. It is partitioned off from a space B that is annular (cylindrical) in top view and accommodates the outer circumferential excess area of No. 11.

After the mold 21 is attached to the wafer 11, a resin is supplied to the space B that accommodates the peripheral surplus area of the mold 21, and the resin is supplied to cover the peripheral surplus area of the front surface 11a of the wafer 11 and the side surface 11c of the wafer 11. Form a member. FIG. 3 is a cross-sectional view schematically showing how the resin member 23 is formed to cover the outer peripheral surplus area of the front surface 11a of the wafer 11 and the side surface 11c.

By supplying resin to the space B of the mold 21 and performing treatments such as heating and pressurization, the resin can be cured and an annular (cylindrical) resin member 23 surrounding the wafer 11 can be formed. Although there are no major restrictions on the type of resin used as a raw material for the resin member 23, it is preferable to use, for example, epoxy resin.

As described above, the partition portion 21c is formed at a height corresponding to the protruding electrode 15a. Therefore, the portion of the resin member 23 that covers the outer peripheral surplus area is also formed to have a thickness corresponding to the height of the protruding electrode 15a. More specifically, the thickness of the portion of the resin member 23 that covers the peripheral surplus area is equal to, slightly larger than, or slightly smaller than the distance from the surface 11a of the wafer 11 to the apex of the protruding electrode 15a. Note that if a method such as compression molding is employed, another mold for closing the upper part of the space B will be prepared.

After forming the resin member 23, the mold 21 is removed from the wafer 11 and the resin member 23. FIG. 4 is a cross-sectional view schematically showing a state in which the mold 21 is removed from the wafer 11 and the resin member 23. In addition, in this embodiment, the annular resin member 23 was formed that completely covers the outer circumferential excess area of the front surface 11a of the wafer 11 and the side surface 11c of the wafer 11. It may be formed so as to partially cover both the surplus area and the side surface of the wafer.

After forming the resin member 23, a protective tape is applied to a portion of the resin member 23 that covers the excess outer peripheral area (protective tape applying step). FIG. 5 is a cross-sectional view schematically showing a state in which the protective tape 25 is attached to the resin member 23. As shown in FIG. The protective tape 25 includes, for example, a film-like base material and a glue layer (adhesive layer) provided on one side of the base material, and has a disc-like shape with a diameter equal to or larger than that of the wafer 11. is formed.

The base material of the protective tape 25 is made of, for example, polyolefin, polyvinyl chloride, polyethylene terephthalate, or the like. For the adhesive layer of the protective tape 25, an acrylic or rubber material is used, for example. By bringing the adhesive layer of the protective tape 25 into close contact with the resin member 23, the protective tape 25 can be attached to the resin member 23. Note that the thickness of the adhesive layer of the protective tape 25 according to this embodiment is smaller than the height of the protruding electrode 15a.

In this embodiment, as shown in FIG. 5, a protective tape 25 is formed by closely adhering an adhesive layer to both the surface 23a of the resin member 23 covering the outer circumferential excess area and the portion corresponding to the apex of the protruding electrode 15a. Attach. As described above, the thickness of the portion of the resin member 23 that covers the outer peripheral surplus area corresponds to the height of the protruding electrode 15a, and the thickness of the portion corresponding to the surface 23a of the resin member 23 and the apex of the protruding electrode 15a, The difference in height is sufficiently small.

Therefore, almost no level difference occurs in the protective tape 25 that is attached to both the surface 23a of the resin member 23 and the portion corresponding to the apex of the protruding electrode 15a. Therefore, both the device area on the front surface 11a of the wafer 11 and the peripheral surplus area on the front surface 11a of the wafer 11 can be appropriately held via the protective tape 25 and the resin member 23.

After attaching the protective tape 25 to the portion of the resin member 23 that covers the outer peripheral surplus area, the back surface 11b of the wafer 11 is ground (grinding step). FIG. 6 is a side view schematically showing how the back surface 11b of the wafer 11 is ground. However, in FIG. 6, for convenience of explanation, the wafer 11 and its accompanying components are shown in cross section.

When grinding the wafer 11, for example, a grinding device 2 shown in FIG. 6 is used. The grinding device 2 includes a chuck table (holding table) 4 that holds the wafer 11. The chuck table 4 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis that is generally parallel to the vertical direction. Further, a moving mechanism (not shown) is provided below the chuck table 4, and the chuck table 4 is moved in the horizontal direction by this moving mechanism.

A part of the upper surface of the chuck table 4 is formed porous using a material such as ceramics, and functions as a holding surface 4a that holds the protective tape 25 attached to the resin member 23 (and protruding electrode 15a). do. The holding surface 4a is connected to a suction source (not shown) via a flow path (not shown) formed inside the chuck table 4. By applying negative pressure from a suction source to the holding surface 4a, the protective tape 25 is attracted to the holding surface 4a, and the front surface 11a side of the wafer 11 is held on the chuck table 4 via the protective tape 25 and the resin member 23. .

A grinding unit 6 is arranged above the chuck table 4. The grinding unit 6 includes a spindle housing (not shown) supported by a lifting mechanism (not shown). A spindle 8 serving as a rotating shaft is rotatably accommodated in the spindle housing, and a disc-shaped mount 10 is fixed to the lower end of the spindle 8 exposed from the spindle housing.

A grinding wheel (grindstone tool) 12 having approximately the same diameter as the mount 10 is attached to the lower surface of the mount 10. The grinding wheel 12 includes a wheel base 14 made of metal such as aluminum or stainless steel. On the lower surface of the wheel base 14, a plurality of grinding wheels 16 obtained by fixing abrasive grains such as diamond with a binder such as resin are arranged in an annular manner.

A rotational drive source (not shown) such as a motor is connected to the upper end side (base end side) of the spindle 8, and the grinding wheel 12 is roughly rotated in the vertical direction by the force generated by this rotational drive source. Rotate around parallel rotation axes. A nozzle (not shown) is provided inside or near the grinding unit 6 for supplying a grinding liquid such as pure water to the wafer 11 and the like.

When grinding the back surface 11b of the wafer 11, first, the protective tape 25 is brought into contact with the holding surface 4a of the chuck table 4, and negative pressure from a suction source is applied. Thereby, the wafer 11 is held on the chuck table 4 via the protective tape 25 and the resin member 23. In this embodiment, as described above, since there is almost no step difference in the protective tape 25, the entire protective tape 25 is brought into contact with the holding surface 4a, and both the device area and the outer peripheral surplus area of the wafer 11 are chucked. It can be held properly on table 4.

After the wafer 11 is held by the chuck table 4, the chuck table 4 is moved below the grinding unit 6. Then, as shown in FIG. 6, the chuck table 4 and the grinding wheel 12 are rotated, and the spindle housing (spindle 8, grinding wheel 12) is lowered while supplying the grinding fluid to the back surface 11b of the wafer 11.

The speed of descent of the spindle housing is adjusted within a range where the lower surface of the grinding wheel 16 is pressed against the back surface 11b of the wafer 11 with appropriate pressure. Thereby, the back surface 11b can be ground to make the wafer 11 thinner. Note that in this embodiment, the resin member 23 is also ground at the same time as the wafer 11. This grinding is continued until the wafer 11 reaches a predetermined thickness (finished thickness).

As described above, in the wafer processing method according to the present embodiment, the resin member 23 is formed in which the portion covering the outer peripheral surplus region has a thickness corresponding to the protruding electrode 15a, and then the outer peripheral surplus region of the resin member 23 is covered. Since the protective tape 25 is attached to the surface of the wafer 11 on the chuck table (holding table) 4, there is no need to use a protective tape with an adhesive layer that is thicker than the height of the protruding electrodes 15a. can be held properly.

In other words, unlike the case where only a protective tape with a small (thin) adhesive layer is used without using the resin member 23, the difference in height on the surface 11a side of the wafer 11 is sufficiently small, so when grinding The possibility of damage to the wafer 11 due to loads applied to the area is also reduced. Furthermore, the adhesive of the protective tape does not remain in the gap caused by the protruding electrode 15a, unlike when using a protective tape having a glue layer that is thicker (thicker) than the height of the protruding electrode 15a.

Further, in this embodiment, since the annular resin member 23 is provided that covers the entire side surface 11c of the wafer 11, the edge of the wafer 11 including the side surface 11c is It is possible to suppress the occurrence of defects called edge chipping, where parts are chipped.

Note that the present invention is not limited to the description of the embodiments described above, and can be implemented with various modifications. For example, in the embodiment described above, the resin member 23 is formed using the mold 21, but the resin member 23 that partially covers the wafer 11 can also be formed using other methods such as inkjet.

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

11: Wafer 11a: Front surface 11b: Back surface 11c: Side surface 13: Planned dividing line (street)
15: Device 15a: Protruding electrode (bump)
21: Mold 21a: Bottom 21b: Side 21c: Partition 23: Resin member 23a: Surface 25: Protective tape A: Space B: Space 2: Grinding device 4: Chuck table (holding table)
4a: Holding surface 6: Grinding unit 8: Spindle 10: Mount 12: Grinding wheel (grindstone tool)
14: Wheel base 16: Grinding wheel

Claims (2)

A surface comprising a device region in which a device having a plurality of protruding electrodes is formed in each of a plurality of regions partitioned by intersecting planned division lines, and an outer peripheral surplus region surrounding the device region, and a side opposite to the surface. A wafer processing method used when processing a wafer including a back surface and a side surface connecting the outer peripheral surplus area of the front surface and the back surface,
By supplying and curing the resin so as to partially or completely cover the excess outer region and the side surface of the front surface of the wafer, the portion covering the excess outer circumference region has a thickness corresponding to the protruding electrode. a resin member forming step of forming a resin member having
After performing the resin member forming step, a protective tape applying step of applying protective tape to the portion of the resin member covering the outer peripheral surplus area and the plurality of protruding electrodes ;
A method for processing a wafer, comprising: after carrying out the step of applying the protective tape, holding the front side of the wafer on a holding table via the protective tape and the resin member, and grinding the back side of the wafer. 2. The wafer processing method according to claim 1, wherein in the resin member forming step, the resin is supplied to a mold attached to the wafer.

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