JP2024017800A - Processing method of workpiece - Google Patents

Abstract

The present invention provides a method for processing a workpiece that can easily reduce variations in the thickness of the workpiece after grinding. [Solution] A method for processing a workpiece, including a fixing step of fixing a protective member on the front side of the workpiece, and a first holding step of holding the back side of the workpiece with a chuck table after the fixing step. and a first grinding step in which, after the first holding step, a grinding wheel including a grinding wheel and a chuck table are relatively approached in a rotated state, and the protection member is ground with the grinding wheel; After that, there is a second holding step in which the front side of the workpiece is held on the chuck table via a protection member, and after the second holding step, the grinding wheel and the chuck table are relatively approached in a rotated state. , a second grinding step of grinding the back side of the workpiece with a grinding wheel. [Selection diagram] Figure 3

Description

The present invention relates to a method for processing a workpiece such as a wafer.

By dividing a wafer on which a plurality of devices are formed into individual pieces, device chips including devices are manufactured. Further, a package substrate is formed by mounting a plurality of device chips on a predetermined substrate and sealing the mounted device chips with a resin layer (molding resin). By dividing this package substrate into individual pieces, a package device including a plurality of packaged device chips is manufactured. Device chips and package devices are incorporated into various electronic devices such as mobile phones and personal computers.

In recent years, with the miniaturization of electronic devices, there has been a demand for thinner device chips and packaged devices. Therefore, a process of thinning the wafer or package substrate by grinding the wafer or package substrate before division using a grinding device is sometimes performed. The grinding device includes a chuck table having a holding surface that holds the workpiece, and a grinding unit that performs grinding on the workpiece, and the grinding unit is equipped with an annular grinding wheel that includes a grinding wheel. . The workpiece is ground and thinned by holding the workpiece on the holding surface of the chuck table and bringing the lower surface (grinding surface) of the grinding wheel into contact with the workpiece while rotating the chuck table and grinding wheel. (See Patent Document 1).

Note that if the entire workpiece is ground and thinned, the rigidity of the workpiece decreases, and the workpiece becomes more likely to be damaged during subsequent handling (transportation, holding, etc.). Therefore, a method has been proposed in which only the central portion of the workpiece is ground to make it thinner. Using this method, the center of the workpiece is thinned and a circular recess is formed in the center of the workpiece, while the outer periphery of the workpiece remains thick without being thinned. and remains as an annular reinforcement. This suppresses a decrease in the rigidity of the workpiece after grinding (see Patent Document 2).

In order to uniformly grind and thin the workpiece, it is necessary to adjust the inclination of the chuck table and grinding wheel with high precision so that the holding surface of the chuck table and the grinding surface of the grinding wheel are parallel. . In addition, a process called self-grinding, in which the holding surface of the chuck table is ground with the grinding surface of a grinding wheel to match the shape of the holding surface and the shape of the grinding surface, is sometimes performed (see Patent Document 3). ). This reduces variations in the thickness of the workpiece after grinding.

Japanese Patent Application Publication No. 2014-124690 Japanese Patent Application Publication No. 2007-19461 Japanese Patent Application Publication No. 2008-60470

As described above, before the grinding wheel grinds the workpiece, the inclinations of the chuck table and the grinding wheel are adjusted. However, precisely adjusting the inclinations of the chuck table and the grinding wheel takes time and effort, and it is often difficult to arrange the holding surface of the chuck table and the grinding surface of the grinding wheel completely parallel. Furthermore, when correcting the shape of the holding surface of the chuck table by self-grinding, a large number of steps are performed to grind the holding surface of the chuck table with a grinding wheel. In this way, in order to reduce variations in the thickness of the workpiece after grinding, complicated preparation work is required.

The present invention has been made in view of this problem, and aims to provide a method for processing a workpiece that can easily reduce variations in the thickness of the workpiece after grinding.

According to one aspect of the present invention, there is provided a method for processing a workpiece, including a fixing step of fixing a protective member on the front side of the workpiece, and after the fixing step, chucking the back side of the workpiece. A first holding step of holding on a table; and after the first holding step, a grinding wheel including a grinding wheel and the chuck table are brought relatively close to each other in a rotated state, and the protection member is ground with the grinding wheel. a first grinding step of holding the surface side of the workpiece on the chuck table via the protection member after the first grinding step; A method for processing a workpiece is provided, comprising: a second grinding step of bringing the grinding wheel and the chuck table relatively close to each other in a rotated state, and grinding the back side of the workpiece with the grinding wheel. Ru.

According to another aspect of the present invention, there is provided a method for processing a workpiece, including a fixing step of fixing a protective member on the surface side of the workpiece; a first holding step of holding the back side of the workpiece with a chuck table having a concave portion curved toward the outer periphery; and after the first holding step, a grinding wheel equipped with a grinding wheel and the chuck table. A first grinding step of grinding the protective member with the grinding wheel while rotating the two relatively close to each other, and after the first grinding step, the surface side of the workpiece is removed through the protective member. a second holding step of holding the work piece on the chuck table; and after the second holding step, the grinding wheel and the chuck table are brought relatively close to each other in a rotated state, and the grinding wheel is used to hold the workpiece. A method for processing a workpiece is provided, including a second grinding step of forming a circular recess in the center of the back side of the workpiece by grinding the center of the back side of the workpiece.

Preferably, the diameter of the protective member is smaller than the diameter of the workpiece and larger than the diameter of the recess. Further, preferably, the workpiece is a disk-shaped wafer.

In the method for processing a workpiece according to one aspect of the present invention, the workpiece is held on a chuck table and the protective member is ground with a grinding wheel, and then the workpiece is reversed and held on the chuck table again. Grind the back side of the workpiece using a grinding wheel. As a result, the non-parallel state between the holding surface and the grinding surface caused by the inclination of the chuck table and the grinding wheel is offset by the thickness variation of the protection member. This makes it possible to reduce variations in the thickness of the workpiece after grinding, even if the adjustment work for bringing the holding surface of the chuck table and the grinding surface of the grinding wheel into a strictly parallel state is omitted.

It is a perspective view showing a workpiece. It is a perspective view showing a grinding device. It is a flowchart which shows the processing method of a workpiece. FIG. 4(A) is a perspective view showing the workpiece in the fixing step, and FIG. 4(B) is a partially sectional front view showing a part of the workpiece in the fixing step. FIG. 5(A) is a partially sectional front view showing the grinding device in the first holding step, and FIG. 5(B) is a partially sectional front view showing the grinding device in the first grinding step. FIG. 6(A) is a partially sectional front view showing the grinding device in the second holding step, and FIG. 6(B) is a partially sectional front view showing the grinding device in the second grinding step. FIG. 3 is a cross-sectional view showing the workpiece after the second grinding step. FIG. 2 is a partially sectional front view showing the grinding device. It is a flowchart which shows the processing method of a workpiece. FIG. 10(A) is a partially sectional front view showing the grinding device in the first holding step, and FIG. 10(B) is a partially sectional front view showing the grinding device in the first grinding step. FIG. 11(A) is a partially sectional front view showing the grinding device in the second holding step, and FIG. 11(B) is a partially sectional front view showing the grinding device in the second grinding step. FIG. 3 is a cross-sectional view showing the workpiece after the second grinding step.

(First embodiment)
Hereinafter, embodiments according to one aspect of the present invention will be described with reference to the accompanying drawings. First, a configuration example of a workpiece that can be processed by the workpiece processing method according to the present embodiment will be described. FIG. 1 is a perspective view showing a workpiece 11. As shown in FIG.

For example, the workpiece 11 is a disk-shaped wafer made of a semiconductor material such as single crystal silicon, and includes a front surface (first surface) 11a and a back surface (second surface) 11b that are generally parallel to each other. The workpiece 11 is divided into a plurality of rectangular regions by a plurality of streets (dividing lines) 13 arranged in a grid pattern so as to intersect with each other. Further, on the surface 11a side of the area divided by the streets 13, devices 15 such as IC (Integrated Circuit), LSI (Large Scale Integration), LED (Light Emitting Diode), MEMS (Micro Electro Mechanical Systems) devices, etc. are installed. It is formed.

The workpiece 11 includes a substantially circular device region 17 in which a plurality of devices 15 are formed, and an annular peripheral surplus region 19 surrounding the device region 17 on the surface 11a side. The peripheral surplus region 19 corresponds to a band-shaped region having a predetermined width (for example, about 2 mm) including the peripheral edge of the surface 11a, and no device 15 is formed in the peripheral surplus region 19. In FIG. 1, the virtual boundary between the device region 17 and the peripheral surplus region 19 is shown by a broken line.

By dividing the workpiece 11 into a grid pattern along the streets 13, a plurality of device chips each including a device 15 are manufactured. Further, by grinding the workpiece 11 to make it thinner before dividing the workpiece 11, a thinned device chip can be obtained.

Note that there are no restrictions on the material, shape, structure, size, etc. of the workpiece 11. For example, the workpiece 11 may be a substrate (wafer) made of a semiconductor other than silicon (GaAs, InP, GaN, SiC, etc.), glass (silica glass, borosilicate glass, etc.), ceramics, resin, metal, etc. . Furthermore, there are no restrictions on the type, quantity, shape, structure, size, arrangement, etc. of the devices 15, and the device 15 may not be formed on the workpiece 11.

Further, the workpiece 11 may be a package substrate such as a CSP (Chip Size Package) substrate or a QFN (Quad Flat Non-leaded package) substrate. For example, a package substrate is formed by sealing a plurality of device chips mounted on a predetermined substrate with a resin layer (molding resin). By dividing the package substrate into individual pieces, a package device including a plurality of packaged device chips is manufactured.

A grinding device is used to grind the workpiece 11. FIG. 2 is a perspective view showing the grinding device 2. As shown in FIG. Note that the X-axis direction (first horizontal direction) and the Y-axis direction (second horizontal direction) are directions perpendicular to each other. Further, the Z-axis direction (processing feed direction, height direction, vertical direction, up-down direction) is a direction perpendicular to the X-axis direction and the Y-axis direction.

The grinding device 2 includes a chuck table (holding table) 4 that holds a workpiece 11 . The upper surface of the chuck table 4 is a flat surface formed along a horizontal plane (XY plane), and constitutes a holding surface 4a that holds the workpiece 11.

A moving mechanism (not shown) and a rotational drive source (not shown) are connected to the chuck table 4. The moving mechanism is constituted by, for example, a ball screw type moving mechanism or a turntable, and moves the chuck table 4 along the horizontal direction (XY plane direction). Further, the rotational drive source is constituted by a motor or the like, and rotates the chuck table 4 around a rotation axis 4b that is generally perpendicular to the radial direction of the holding surface 4a.

Although the shape of the holding surface 4a is illustrated in a simplified manner in FIG. 2, the holding surface 4a is formed in a conical shape with the center of the holding surface 4a as its apex, and the shape of the holding surface 4a is It is slightly sloped. The chuck table 4 is arranged in a slightly inclined state so that a part of the holding surface 4a from the center to the outer peripheral edge thereof is along a horizontal plane (XY plane). Therefore, the rotation axis 4b of the chuck table 4 is slightly inclined with respect to the Z-axis direction. For example, when the diameter of the holding surface 4a is approximately 290 mm or more and 310 mm or less, the difference in height between the center and the outer peripheral edge of the holding surface 4a (corresponding to the height of a cone) is set to approximately 20 μm or more and 40 μm or less.

The chuck table 4 includes a cylindrical frame (main body) 6 made of metal such as SUS (stainless steel), glass, ceramics, resin, or the like. A columnar recess (groove) 6b is provided in the center of the upper surface 6a of the frame 6. A disk-shaped holding member 8 made of a porous material such as porous ceramics is fitted into the recess 6b. The holding member 8 includes therein a large number of pores (channels) communicating from the upper surface to the lower surface of the holding member 8.

The upper surface of the holding member 8 constitutes a circular suction surface 8a that suctions the workpiece 11. The upper surface 6a of the frame 6 and the outer periphery of the suction surface 8a are arranged at approximately the same height position, and the upper surface 6a of the frame 6 and the suction surface 8a of the holding member 8 prevent the holding surface 4a of the chuck table 4. is configured. The holding surface 4a (suction surface 8a) is connected to a suction source (not shown) such as an ejector via pores included in the holding member 8, a flow path (not shown) formed in the frame 6, a valve (not shown), etc. )It is connected to the.

A grinding unit 10 for grinding a workpiece 11 is provided above the chuck table 4. The grinding unit 10 includes a cylindrical spindle 12 arranged along the Z-axis direction. A disc-shaped wheel mount 14 made of metal such as SUS (stainless steel) is fixed to the tip (lower end) of the spindle 12. Further, a rotational drive source (not shown) such as a motor is connected to the base end (upper end) of the spindle 12.

An annular grinding wheel 16 for grinding the workpiece 11 is mounted on the lower surface side of the wheel mount 14 . For example, the grinding wheel 16 is fixed to the wheel mount 14 by a fastener such as a bolt.

The grinding wheel 16 includes an annular wheel base 18 . The wheel base 18 is made of metal such as aluminum or stainless steel, and is formed to have approximately the same diameter as the wheel mount 14. The upper surface side of the wheel base 18 is fixed to the lower surface side of the wheel mount 14. Further, a plurality of grinding wheels 20 are fixed to the lower surface side of the wheel base 18. For example, the plurality of grinding wheels 20 are formed in the shape of a rectangular parallelepiped, and are arranged at approximately equal intervals along the outer periphery of the wheel base 18 .

The grinding wheel 20 is formed by fixing abrasive grains made of diamond, cBN (cubic boron nitride), or the like with a bonding material such as metal bond, resin bond, vitrified bond, or the like. However, there are no restrictions on the material, shape, structure, size, etc. of the grinding wheel 20. Further, the number of grinding wheels 20 can also be set arbitrarily.

The lower surface of the grinding wheel 20 constitutes a grinding surface 20a that grinds the workpiece 11. When the spindle 12 is rotated, the grinding wheel 16 rotates around a rotation axis 16a that is generally parallel to the Z-axis direction. As a result, each of the plurality of grinding wheels 20 rotates (swivels) along an annular rotation path centered on the rotation axis 16a. The workpiece 11 is ground by bringing the grinding surface 20a of the grinding wheel 20 into contact with the workpiece 11 while rotating the grinding wheel 16.

Next, details of the method for processing the workpiece 11 in this embodiment will be explained. Below, as an example, a case will be described in which the back surface 11b side of the workpiece 11 is ground to make the workpiece 11 thinner. FIG. 3 is a flowchart showing a method for processing the workpiece 11. As shown in FIG.

In this embodiment, the preparation work for reducing thickness variations of the workpiece 11 is omitted. Specifically, the work of adjusting the inclinations of the chuck table 4 and the grinding wheel 16 with high precision so that the holding surface 4a of the chuck table 4 and the grinding surface 20a of the grinding wheel 20 are parallel to each other is not performed. Further, self-grinding is not performed by grinding the holding surface 4a of the chuck table 4 with the grinding surface 20a of the grinding wheel 20 to match the shape of the holding surface 4a and the shape of the grinding surface 20a. Thereby, after the grinding wheel 16 is mounted on the grinding unit 10, grinding of the workpiece 11 can be started immediately.

When grinding the workpiece 11, first, the protection member 21 is fixed to the surface 11a side of the workpiece 11 (fixing step S11). FIG. 4(A) is a perspective view showing the workpiece 11 in the fixing step S11, and FIG. 4(B) is a partially sectional front view showing a part of the workpiece 11 in the fixing step S11.

In the fixing step S11, the protection member 21 is fixed to the surface 11a side of the workpiece 11. The protection member 21 is a circular sheet-like or plate-like member having approximately the same diameter as the workpiece 11, and includes a first surface 21a and a second surface 21b.

For example, a circular tape formed to have approximately the same diameter as the workpiece 11 is used as the protection member 21. Specifically, the protection member 21 includes a film-like base material and an adhesive layer (glue layer) provided on the base material. The base material is made of a resin such as polyolefin, polyvinyl chloride, or polyethylene terephthalate, and the adhesive layer is made of an epoxy, acrylic, or rubber adhesive. Note that the adhesive layer may be an ultraviolet curable resin that is cured by irradiation with ultraviolet rays. The adhesive layer is exposed on the first surface 21a side of the protection member 21, and the base material is exposed on the second surface 21b side of the protection member 21.

For example, in the fixing step S11, the workpiece 11 is supported by the support table 22 (see FIG. 4(B)), and the protection member 21 is attached to the surface 11a side of the workpiece 11 by the fixing unit 24 (see FIG. 4(B)). is fixed. The upper surface of the support table 22 is a flat surface that is generally parallel to the horizontal plane, and constitutes a support surface 22a that supports the workpiece 11. The workpiece 11 is placed on the support table 22 so that the front surface 11a side is exposed upward and the back surface 11b side faces the support surface 22a.

The fixing unit 24 includes a columnar main body 26 and a cylindrical roller 28 attached to the tip of the main body 26. The roller 28 is attached to the main body 26 via a support shaft 30 arranged along the length of the roller 28, and is supported in a freely rotatable state around the support shaft 30. Note that the length of the roller 28 is equal to or longer than the diameter of the workpiece 11.

When attaching the protective member 21 to the workpiece 11, the roller 28 is attached to the second Roll it on the workpiece 11 while pressing it against the surface 21b. Thereby, the protection member 21 is pressed against the surface 11a side of the workpiece 11 and is attached so as to cover the entire surface 11a side of the workpiece 11. As a result, the surface 11a side of the workpiece 11 and the device 15 are protected by the protection member 21.

However, there is no limit to the method of fixing the protective member 21. For example, after attaching a rectangular protection member 21 capable of covering the entire surface 11a side of the workpiece 11 to the surface 11a side of the workpiece 11, the protection member 21 is attached to the outer peripheral edge of the workpiece 11. The circular protection member 21 may be fixed to the workpiece 11 by cutting along the line.

Next, the back surface 11b side of the workpiece 11 is held by the chuck table 4 (first holding step S12). FIG. 5(A) is a partially sectional front view showing the grinding device 2 in the first holding step S12.

In the first holding step S12, first, the workpiece 11 is placed on the holding surface 4a of the chuck table 4. Specifically, the workpiece 11 is arranged so that the front surface 11a side (protection member 21 side) faces upward and the back surface 11b side faces the holding surface 4a. At this time, the workpiece 11 is positioned concentrically with the holding surface 4a so that the rotation axis 4b of the chuck table 4 passes through the center of the workpiece 11. In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface 4a, the workpiece 11 is suction-held by the chuck table 4.

Next, the chuck table 4 is placed below the grinding wheel 16. Specifically, the chuck table 4 is positioned so that the centers of the workpiece 11 and the protection member 21 and the rotation path of the grinding wheel 20 overlap in the Z-axis direction. At this time, a region of the second surface 21b (exposed surface) of the protection member 21 that overlaps the rotation path of the grinding wheel 20 in the Z-axis direction is contacted and ground by the grinding wheel 20 in the first grinding step S13, which will be described later. This corresponds to the contact area (ground area) 21c.

Note that the inclinations of the chuck table 4 and the grinding wheel 16 are not strictly adjusted before and after the first holding step S12. Further, before the first holding step S12, self-grinding in which the holding surface 4a is ground with the grinding wheel 20 is not performed. Therefore, a region of the holding surface 4a that overlaps with the rotation path of the grinding wheel 20 and a contact region 21c of the protection member 21 are non-parallel to the grinding surface 20a of the grinding wheel 20. FIG. 5A shows an example in which the chuck table 4 is tilted so that the distance between the center of the protection member 21 and the grinding wheel 20 is shorter than the distance between the outer circumference of the protection member 21 and the grinding wheel 20. is illustrated.

Next, the protection member 21 is ground with the grinding wheel 20 (first grinding step S13). FIG. 5(B) is a partially sectional front view showing the grinding device 2 in the first grinding step S13.

In the first grinding step S13, the chuck table 4 is rotated around the rotation axis 4b, and the grinding wheel 16 is rotated around the rotation axis 16a. In this state, the grinding wheel 16 is lowered along the rotating shaft 16a (Z-axis direction) to bring the chuck table 4 and the grinding wheel 16 relatively close to each other. As a result, the grinding surfaces 20a of the plurality of rotating grinding wheels 20 come into contact with the contact area 21c of the protection member 21, and the entire second surface 21b side of the protection member 21 is ground.

When the protection member 21 is ground with the grinding wheel 16, the contact area 21c of the protection member 21, which was non-parallel to the grinding surface 20a before grinding, becomes parallel to the grinding surface 20a. The thickness of the protective member 21 is different between the central portion and the outer peripheral portion. For example, when the chuck table 4 and the grinding wheel 16 are arranged as shown in FIG. .

When the protection member 21 is ground to a predetermined thickness, the grinding unit 10 is raised and the grinding wheel 20 is separated from the protection member 21. This completes the grinding of the protection member 21. The protective member 21 after being ground has thickness variations due to the inclination of the chuck table 4 and the grinding wheel 16.

Next, the front surface 11a side of the workpiece 11 is held by the chuck table 4 via the protection member 21 (second holding step S14). FIG. 6(A) is a partially sectional front view showing the grinding device 2 in the second holding step S14.

In the second holding step S14, first, the workpiece 11 is lifted from the holding surface 4a while the inclinations of the chuck table 4 and the grinding wheel 16 are maintained unchanged. Then, the workpiece 11 is turned upside down and placed on the holding surface 4a again. As a result, the front surface 11a side (protection member 21 side) of the workpiece 11 faces the holding surface 4a, and the back surface 11b side of the workpiece 11 is exposed upward.

Note that the workpiece 11 is arranged concentrically with the holding surface 4a so that the rotation axis 4b of the chuck table 4 passes through the center of the workpiece 11. In this state, when the suction force of the suction source is applied to the holding surface 4a, the workpiece 11 is suction-held by the chuck table 4 via the protection member 21.

Next, the chuck table 4 is placed below the grinding wheel 16. Specifically, the chuck table 4 is positioned so that the centers of the workpiece 11 and the protection member 21 and the rotation path of the grinding wheel 20 overlap in the Z-axis direction. At this time, a region of the back surface 11b of the workpiece 11 that overlaps the rotation path of the grinding wheel 20 in the Z-axis direction is a contact region (to be ground Corresponds to area) 11c.

When the workpiece 11 is held by the chuck table 4, the protection member 21 is deformed so that the second surface 21b of the protection member 21 aligns with the holding surface 4a. Further, the workpiece 11 fixed to the protection member 21 is deformed along the first surface 21a of the protection member 21. That is, the shape of the second surface 21b (see FIG. 5(B)) of the protection member 21 before the workpiece 11 is held by the chuck table 4 is reflected in the shape of the front surface 11a and the back surface 11b of the workpiece 11. Ru. As a result, the contact area 11c of the workpiece 11 is arranged parallel to the grinding surface 20a of the grinding wheel 20.

Next, the back surface 11b side of the workpiece 11 is ground using the grinding wheel 20 (second grinding step S15). FIG. 6(B) is a partially sectional front view showing the grinding device 2 in the second grinding step S15.

In the second grinding step S15, the chuck table 4 is rotated around the rotation axis 4b, and the grinding wheel 16 is rotated around the rotation axis 16a. In this state, the grinding wheel 16 is lowered along the rotating shaft 16a (Z-axis direction) to bring the chuck table 4 and the grinding wheel 16 relatively close to each other. As a result, the grinding surfaces 20a of the plurality of rotating grinding wheels 20 come into contact with the contact area 11c of the workpiece 11, and the entire back surface 11b side of the workpiece 11 is ground.

When the workpiece 11 is ground with the grinding wheel 16 as described above, the workpiece 11 is uniformly ground while the contact area 11c of the workpiece 11 and the grinding surface 20a of the grinding wheel 20 are maintained in a parallel state. Become thinner. As a result, variations in the thickness of the workpiece 11 after grinding are less likely to occur. Then, when the workpiece 11 is ground to a predetermined thickness (finish thickness), the grinding unit 10 rises and the grinding wheel 20 leaves the back surface 11b of the workpiece 11. This completes the grinding of the workpiece 11. Note that the finished thickness corresponds to the target value of the thickness of the workpiece 11 after grinding.

FIG. 7 is a sectional view showing the workpiece 11 after the second grinding step S15. After grinding the workpiece 11, when the workpiece 11 is released from being held by the chuck table 4, the workpiece 11 and the protection member 21 are deformed, and the workpiece 11 returns to a flat state. As a result, a thinned workpiece 11 having a uniform thickness is obtained.

As described above, in the method for processing a workpiece according to the present embodiment, after the workpiece 11 is held by the chuck table 4 and the protection member 21 is ground by the grinding wheel 20, the workpiece 11 is reversed and the workpiece 11 is turned over again. The workpiece 11 is held by the chuck table 4, and the back surface 11b side of the workpiece 11 is ground by the grinding wheel 20. As a result, the non-parallel state between the holding surface 4a and the grinding surface 20a caused by the inclination of the chuck table 4 and the grinding wheel 16 is offset by the thickness variation of the protection member 21. Thereby, even if the adjustment work of bringing the holding surface 4a of the chuck table 4 and the grinding surface 20a of the grinding wheel 20 into a strictly parallel state is omitted, variations in the thickness of the workpiece 11 after being ground can be reduced.

Note that the structure, method, etc. according to this embodiment can be modified and implemented as appropriate without departing from the scope of the purpose of the present invention.

(Second embodiment)
Next, another example of the method of grinding the workpiece 11 will be described. If the entire workpiece 11 is ground and thinned, the rigidity of the workpiece 11 will decrease, and the workpiece 11 will be easily damaged when handling (transporting, holding, etc.) the workpiece 11 after grinding. Become. Therefore, in this embodiment, only the central portion of the back surface 11b of the workpiece 11 is subjected to the grinding process.

FIG. 8 is a partially sectional front view showing a grinding device 32 that grinds only the center portion of the workpiece 11. As shown in FIG. Note that the configuration and functions of the grinding device 32 are the same as those of the grinding device 2 (see FIG. 2) except for the matters described below.

The grinding device 32 includes a chuck table (holding table) 34 that holds the workpiece 11. The upper surface of the chuck table 34 constitutes a holding surface 34a that holds the workpiece 11.

A recess (groove) 34b is provided on the side of the holding surface 34a of the chuck table 34, which curves from the center of the holding surface 34a toward the outer periphery. The recess 34b is formed in a circular shape so as to surround the center of the holding surface 34a in a plan view, and the recess 34b is not formed at the center and outer periphery of the holding surface 34a. For example, the recess 34b is formed into a substantially W-shape in cross-sectional view so that it is deepest near the midpoint between the center and the outer peripheral edge of the holding surface 34a. By providing the recess 34b, the holding surface 34a is formed into a curved shape that curves toward the inside (lower side) of the chuck table 34.

Although the depth of the recess 34b is exaggerated in FIG. 8 for convenience of explanation, the actual curvature of the holding surface 34a is slight. For example, the maximum depth of the recess 34b is set to 1 μm or more and 20 μm or less.

A moving mechanism (not shown) and a rotational drive source (not shown) are connected to the chuck table 34. The moving mechanism includes, for example, a ball screw type moving mechanism or a turntable, and moves the chuck table 34 in the horizontal direction (XY plane direction). Further, the rotational drive source is constituted by a motor or the like, and rotates the chuck table 34 around a rotation axis 34c that is generally parallel to the radial direction (Z-axis direction) of the holding surface 34a.

The chuck table 34 includes a cylindrical frame (main body) 36. A columnar recess (groove) 36b is provided in the center of the upper surface 36a of the frame 36, and a disc-shaped holding member 38 is fitted into the recess 36b. Note that examples of materials for the frame 36 and the holding member 38 are the same as those for the frame 6 and the holding member 8 (see FIG. 2).

The upper surface of the holding member 38 constitutes a circular suction surface 38a that suctions the workpiece 11. The above-described recess 34b is formed on the upper surface 36a side of the frame body 36 and on the suction surface 38a side of the holding member 38. The upper surface 36a of the frame 36 and the suction surface 38a of the holding member 38 constitute a holding surface 34a of the chuck table 34. The holding surface 34a (suction surface 38a) is connected to a suction source (not shown) such as an ejector via pores included in the holding member 38, a flow path 36c formed in the frame 36, a valve (not shown), etc. has been done.

A grinding unit 40 for grinding the workpiece 11 is provided above the chuck table 34 . The grinding unit 40 includes a spindle 42 and a wheel mount 44. The shape, structure, function, etc. of the spindle 42 and the wheel mount 44 are the same as those of the spindle 12 and the wheel mount 14 (see FIG. 2), respectively.

A grinding wheel 46 is mounted on the lower surface side of the wheel mount 44. The grinding wheel 46 includes a wheel base 48 and a plurality of grinding wheels 50. Note that the shape, structure, function, etc. of the wheel base 48 and the grinding wheel 50 are the same as those of the wheel base 18 and the grinding wheel 20 (see FIG. 2), respectively. The lower surface of the grinding wheel 50 constitutes a grinding surface 50a that grinds the workpiece 11.

When the spindle 42 is rotated, the grinding wheel 46 rotates around the rotation axis 46a. As a result, each of the plurality of grinding wheels 50 rotates (swivels) along an annular rotation path centered on the rotation axis 46a. The workpiece 11 is ground by bringing the grinding surface 50a of the grinding wheel 50 into contact with the workpiece 11 while rotating the grinding wheel 46.

Next, details of the method for processing the workpiece 11 in this embodiment will be explained. In this embodiment, a circular recess is formed on the back surface 11b side of the workpiece 11 by grinding only the central portion of the back surface 11b side of the workpiece 11. FIG. 9 is a flowchart showing a method for processing the workpiece 11.

First, the protection member 21 is fixed to the surface 11a side of the workpiece 11 (fixing step S21). The contents of the fixing step S21 are the same as the above-described fixing step S11 (see FIGS. 4(A) and 4(B)).

However, the diameter of the protection member 21 is set to be smaller than the diameter of the workpiece 11. For example, a protection member 21 having approximately the same diameter as the device region 17 (see FIG. 1) of the workpiece 11 is attached to the surface 11a side of the workpiece 11. As a result, the plurality of devices 15 formed in the device region 17 are covered and protected by the protection member 21, and the outer peripheral surplus region 19 is maintained in an exposed state.

Note that the diameter of the protection member 21 is preferably larger than the diameter of a recess 11d (see FIG. 11(B)) formed in the workpiece 11 in the second grinding step S25, which will be described later. Thereby, when grinding the workpiece 11, the entire area to be ground can be reliably supported and protected by the protection member 21.

Next, the back surface 11b side of the workpiece 11 is held by the chuck table 34 (first holding step S22). FIG. 10(A) is a partially sectional front view showing the grinding device 32 in the first holding step S22.

In the first holding step S22, first, the workpiece 11 is placed on the holding surface 34a of the chuck table 34. Specifically, the workpiece 11 is arranged so that the front surface 11a side (protection member 21 side) faces upward and the back surface 11b side faces the holding surface 34a. At this time, the workpiece 11 is positioned concentrically with the holding surface 34a so that the rotating shaft 34c of the chuck table 34 passes through the center of the workpiece 11. In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface 34a, the workpiece 11 is suction-held by the chuck table 34.

When the workpiece 11 is held by the chuck table 34, the workpiece 11 is deformed so that the back surface 11b of the workpiece 11 is along the holding surface 34a. Furthermore, the protection member 21 fixed to the workpiece 11 deforms along the surface 11a of the workpiece 11. That is, the curvature of the holding surface 34a is reflected on the workpiece 11 and the protection member 21. As a result, the protective member 21 is in a state in which the central portion and the outer peripheral portion are disposed higher than the other regions.

Next, the chuck table 34 is placed below the grinding wheel 46. Note that the grinding wheel 46 is configured such that the diameter of the rotation path of the grinding wheel 50 is less than the radius of the workpiece 11 and greater than or equal to the radius of the protection member 21. The chuck table 34 is positioned such that the center and outer peripheral edge of the protection member 21 overlap with the rotation path of the grinding wheel 50. At this time, a region of the second surface 21b of the protection member 21 that overlaps the rotation path of the grinding wheel 50 in the Z-axis direction becomes a contact region 21c where the grinding wheel 50 contacts and is ground in the first grinding step S23, which will be described later. Equivalent to.

Further, the grinding wheel 46 is arranged such that the rotation axis 46a is slightly inclined with respect to the rotation axis 34c (Z-axis direction) of the chuck table 34. Specifically, in the grinding wheel 46, a grinding wheel 50 fixed to the front end side of the wheel base 48 (the near side in FIG. 10(A)) is fixed to the rear end side of the wheel base 48 (the near side in FIG. 10(A)). It is tilted at a predetermined angle in the YZ plane so that it is positioned below the grinding wheel 50 fixed on the back side).

Note that although the inclination of the grinding wheel 46 is illustrated in an exaggerated manner in FIG. 10(A) for convenience of explanation, the inclination of the actual grinding wheel 46 is slight. For example, the angle of inclination of the rotating shaft 46a of the grinding wheel 46 with respect to the rotating shaft 34c of the chuck table 34 is 0.001° or more and 0.02° or less.

Strict adjustment of the inclinations of the chuck table 34 and the grinding wheel 46 is not performed before and after the first holding step S22. Further, before the first holding step S22, self-grinding in which the holding surface 34a is ground with a grinding wheel may be performed, but in the self-grinding, a grinding wheel corresponding to the shape and dimensions of the holding surface 34a is used. Ru. Therefore, the grinding wheel used for self-grinding and the grinding wheel 46 used for grinding the workpiece 11 and the protection member 21 have different dimensions. As a result, the region of the holding surface 34a that overlaps with the rotation path of the grinding wheel 50 and the contact region 21c of the protection member 21 are non-parallel to the grinding surface 50a of the grinding wheel 50.

Next, the protection member 21 is ground using the grinding wheel 50 (first grinding step S23). FIG. 10(B) is a partially sectional front view showing the grinding device 32 in the first grinding step S23.

In the first grinding step S23, the chuck table 34 is rotated around the rotation axis 34c, and the grinding wheel 46 is rotated around the rotation axis 46a. In this state, the grinding wheel 46 is lowered along the Z-axis direction, causing the chuck table 34 and the grinding wheel 46 to approach each other relatively. As a result, the grinding surfaces 50a of the plurality of rotating grinding wheels 50 come into contact with the contact area 21c of the protection member 21, and the entire second surface 21b side of the protection member 21 is ground.

When the protection member 21 is ground with the grinding wheel 46, the contact area 21c of the protection member 21, which was non-parallel to the grinding surface 50a before grinding, becomes parallel to the grinding surface 50a. As a result, in-plane thickness variations occur in the protective member 21. For example, the protective member 21 is thinned so that the central portion and the outer peripheral portion are thinner (or thicker) than other regions.

When the protective member 21 is ground to a predetermined thickness, the grinding unit 40 is raised and the grinding wheel 50 is separated from the protective member 21. This completes the grinding of the protection member 21. After grinding, the protective member 21 has thickness variations due to the inclination of the chuck table 34 and the grinding wheel 46.

Next, the front surface 11a side of the workpiece 11 is held by the chuck table 34 via the protection member 21 (second holding step S24). FIG. 11(A) is a partially sectional front view showing the grinding device 32 in the second holding step S24.

In the second holding step S24, first, the workpiece 11 is lifted from the holding surface 34a while the inclinations of the chuck table 34 and the grinding wheel 46 are maintained unchanged. Then, the workpiece 11 is turned upside down and placed on the holding surface 34a again. As a result, the front surface 11a side (protection member 21 side) of the workpiece 11 faces the holding surface 34a, and the back surface 11b side of the workpiece 11 is exposed upward.

Note that the workpiece 11 is arranged concentrically with the holding surface 34a so that the rotation axis 34c of the chuck table 34 passes through the center of the workpiece 11. In this state, when the suction force of the suction source is applied to the holding surface 34a, the workpiece 11 is suction-held by the chuck table 34 via the protection member 21.

Next, the chuck table 34 is placed below the grinding wheel 46. Specifically, the chuck table 34 is arranged so that the centers of the workpiece 11 and the protection member 21 and the rotation path of the grinding wheel 50 overlap in the Z-axis direction. Note that, as described above, the diameter of the rotation path of the grinding wheel 50 is set to be less than the radius of the workpiece 11. Therefore, the outer circumference of the workpiece 11 does not overlap the rotation path of the grinding wheel 50. A region of the back surface 11b of the workpiece 11 that overlaps the rotation path of the grinding wheel 50 in the Z-axis direction corresponds to a contact region 11c where the grinding wheel 50 contacts and grinds in the second grinding step S25, which will be described later. .

When the workpiece 11 is held by the chuck table 34, the protection member 21 deforms so that the second surface 21b of the protection member 21 follows the curved holding surface 34a. Further, the workpiece 11 fixed to the protection member 21 is deformed along the first surface 21a of the protection member 21. That is, the curvature of the holding surface 34a and the variation in the thickness of the protection member 21 are reflected in the shapes of the front surface 11a and the back surface 11b of the workpiece 11. As a result, the contact area 11c of the workpiece 11 is arranged parallel to the grinding surface 50a of the grinding wheel 50.

Next, the back surface 11b side of the workpiece 11 is ground using the grinding wheel 46 (second grinding step S25). FIG. 11(B) is a partially sectional front view showing the grinding device 32 in the second grinding step S25.

In the second grinding step S25, the chuck table 34 is rotated around the rotation axis 34c, and the grinding wheel 46 is rotated around the rotation axis 46a. In this state, the grinding wheel 46 is lowered along the Z-axis direction, causing the chuck table 34 and the grinding wheel 46 to approach each other relatively. As a result, the grinding surfaces 50a of the plurality of rotating grinding wheels 50 come into contact with the contact area 11c of the workpiece 11, and the center portion of the back surface 11b of the workpiece 11 is ground. As a result, a circular recess (groove) 11d is formed in the center of the back surface 11b of the workpiece 11.

When the workpiece 11 is ground with the grinding wheel 46 as described above, the workpiece 11 is uniformly ground while the contact area 11c of the workpiece 11 and the grinding surface 50a of the grinding wheel 50 are maintained in a parallel state. Become thinner. Then, when the workpiece 11 is ground to a predetermined thickness (finish thickness), the grinding unit 40 is raised and the grinding wheel 50 is separated from the workpiece 11. This completes the grinding of the workpiece 11.

FIG. 12 is a sectional view showing the workpiece 11 after the second grinding step S25. When the workpiece 11 is ground by the grinding wheel 46, a circular recess 11d is formed in the center of the back surface 11b of the workpiece 11. On the other hand, the outer peripheral part of the workpiece 11 is not ground and is maintained in a thick state, so that it remains so as to surround the recessed part 11d. As a result, the outer peripheral portion of the workpiece 11 functions as an annular reinforcing portion, and a decrease in rigidity of the workpiece 11 after grinding is suppressed.

After grinding the workpiece 11, when the workpiece 11 is released from being held by the chuck table 34, the workpiece 11 and the protection member 21 are deformed, and the workpiece 11 returns to a flat state. This results in a workpiece 11 having a thinned device region 17 with a uniform thickness.

As described above, in the method for processing a workpiece according to the present embodiment, after the workpiece 11 is held by the chuck table 34 and the protective member 21 is ground by the grinding wheel 50, the workpiece 11 is reversed and the workpiece 11 is turned over again. The workpiece 11 is held by the chuck table 34, and the center portion of the back surface 11b side of the workpiece 11 is ground by the grinding wheel 50. As a result, the non-parallel state between the holding surface 34a and the grinding surface 50a caused by the inclination of the chuck table 34 and the grinding wheel 46 is offset by the thickness variation of the protection member 21. As a result, even if the adjustment work for bringing the holding surface 34a of the chuck table 34 and the grinding surface 50a of the grinding wheel 50 into a strictly parallel state is omitted, variations in the depth of the recessed portion 11d after grinding can be reduced.

Note that the structure, method, etc. according to this embodiment can be modified and implemented as appropriate without departing from the scope of the purpose of the present invention. Further, matters whose explanations are omitted in this embodiment are the same as those in the first embodiment.

11 Workpiece 11a Surface (first surface)
11b Back side (second side)
11c Contact area (ground area)
11d Recess (groove)
13 Street (planned dividing line)
15 Device 17 Device area 19 Surplus outer periphery area 21 Protective member 21a First surface 21b Second surface 21c Contact area (ground area)
2 Grinding device 4 Chuck table (holding table)
4a Holding surface 4b Rotating shaft 6 Frame (main body)
6a Top surface 6b Recess (groove)
8 Holding member 8a Suction surface 10 Grinding unit 12 Spindle 14 Wheel mount 16 Grinding wheel 16a Rotating shaft 18 Wheel base 20 Grinding wheel 20a Grinding surface 22 Support table 22a Support surface 24 Fixing unit 26 Main body 28 Roller 30 Support shaft 32 Grinding device 34 Chuck table (holding table)
34a Holding surface 34b Recess (groove)
34c Rotating shaft 36 Frame (main body)
36a Top surface 36b Recess (groove)
38 Holding member 38a Suction surface 40 Grinding unit 42 Spindle 44 Wheel mount 46 Grinding wheel 46a Rotating shaft 48 Wheel base 50 Grinding wheel 50a Grinding surface

Claims (4)

A method for processing a workpiece,
a fixing step for fixing the protective member on the surface side of the workpiece;
After the fixing step, a first holding step of holding the back side of the workpiece with a chuck table;
After the first holding step, a first grinding step of bringing a grinding wheel including a grinding wheel and the chuck table relatively close to each other in a rotated state, and grinding the protection member with the grinding wheel;
After the first grinding step, a second holding step of holding the front side of the workpiece with the chuck table via the protection member;
After the second holding step, a second grinding step of bringing the grinding wheel and the chuck table relatively close to each other in a rotated state and grinding the back side of the workpiece with the grinding wheel. A method for processing a workpiece, characterized by: A method for processing a workpiece,
a fixing step for fixing the protective member on the surface side of the workpiece;
After the fixing step, a first holding step of holding the back side of the workpiece with a chuck table having a concave portion curved from the center of the holding surface toward the outer periphery;
After the first holding step, a first grinding step of bringing a grinding wheel including a grinding wheel and the chuck table relatively close to each other in a rotated state, and grinding the protection member with the grinding wheel;
After the first grinding step, a second holding step of holding the front side of the workpiece with the chuck table via the protection member;
After the second holding step, the grinding wheel and the chuck table are brought relatively close to each other in a rotated state, and the central part of the back side of the workpiece is ground with the grinding wheel, thereby removing the workpiece. A method for processing a workpiece, comprising: a second grinding step of forming a circular recess in the center of the back side of the workpiece. 3. The method of processing a workpiece according to claim 2, wherein the diameter of the protection member is less than the diameter of the workpiece and larger than the diameter of the recess. 4. The method of processing a workpiece according to claim 1, wherein the workpiece is a disk-shaped wafer.

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