JP6824583B2 - Wafer processing method - Google Patents

Description

The present invention relates to a method for processing a wafer having a device formed on its surface.

A device chip is formed by grinding the back surface of a wafer in which a plurality of devices such as ICs and LSIs are formed on the front surface to thin the wafer to a predetermined thickness, and then dividing the wafer along a predetermined division schedule line. it can. The device chip including the formed device is used for an electronic device such as a mobile phone or a personal computer.

A grinding device is used to grind the back surface of the wafer. The grinding device includes a disk-shaped grinding wheel, a spindle that rotatably supports the grinding wheel, a motor that rotates the spindle, and the like. The grinding wheel is equipped with a plurality of grindstones that come into contact with a workpiece such as a wafer to grind the workpiece.

When grinding the back surface of the wafer using the grinding device, a protective tape is attached to the front surface side of the wafer in advance (see Patent Document 1). By attaching the protective tape to the surface side of the wafer, the device on the surface side of the wafer can be protected in the grinding process. When the wafer is held on the chuck table of the grinding device, the front side of the wafer is directed toward the chuck table in order to expose the back surface side of the wafer. Then, the wafer is held on the chuck table via a protective tape attached to the surface side.

By the way, the variation in the thickness of the protective tape is larger than the variation in the thickness of the wafer. Therefore, when grinding the back surface of the wafer held on the chuck table via the protective tape, the height of the back surface of the wafer varies, which causes a problem that the processing accuracy deteriorates. Further, when electrode bumps or the like are formed on the surface of the wafer, the unevenness of the protective tape becomes large, and the problem becomes remarkable.

Therefore, a method has been proposed in which a protective tape is attached to the front surface side of the wafer, the protective tape is cut with a tool to flatten the surface in contact with the chuck table, and then the back surface side of the wafer is ground. (See Patent Document 2).

Japanese Unexamined Patent Publication No. 2000-288881 Japanese Unexamined Patent Publication No. 2013-21017

A tool cutting device having a chuck table and a tool tool attached to an annular tool wheel is used for flattening the protective tape. The upper surface of the chuck table is a holding surface on which the workpiece is placed, and an annular bite wheel is arranged above the chuck table. The surface of the annular bite wheel facing the holding surface is substantially parallel to the holding surface. The tool tool is attached to the surface of the tool wheel facing the holding surface.

The bite wheel is rotatable around an axis perpendicular to the holding surface. At the time of cutting a tool, the tool wheel is positioned at a height at which the protective tape can be cut with the tool, and then the tool wheel is rotated around the shaft. Then, when the chuck table is linearly moved a plurality of times in the direction in the plane parallel to the holding surface, the protective tape is partially cut and the protective tape is flattened.

When the chuck table is linearly moved so as to pass under the bite wheel, a rut-shaped cutting mark along the rotation direction of the bite wheel is formed on the surface to be cut of the protective tape. Then, when the movement of the chuck table is repeated, the tool tool is guided to the rut-shaped cutting mark, and the protective tape is cut with a tool so that the cutting mark becomes deeper.

If a tool is to be further cut with a deep cutting mark formed on the protective tape, the cutting tool may be caught in the deep cutting mark and the protective tape may be partially peeled off from the wafer, which is a problem.

The present invention has been made in view of such problems, and an object of the present invention is a wafer capable of suppressing peeling of a protective tape attached to the front surface side of a wafer and appropriately grinding the back surface side of the wafer. Is to provide a processing method of.

According to one aspect of the present invention, there is a method for processing a wafer in which a plurality of planned division lines are set on the surface in a grid pattern and devices are formed in a plurality of regions partitioned by the plurality of scheduled division lines. After the protective tape attaching step of attaching the protective tape to the surface of the wafer and the protective tape attaching step, the exposed surface of the protective tape attached to the surface of the wafer is flattened by cutting with a tool. After the flattening step and the flattening step, the front surface side of the wafer is directed toward the chuck table of the grinding device, the chuck table is held by the chuck table via the protective tape, and the back surface side of the wafer is ground. It comprises a grinding step to bring the wafer to a predetermined thickness, the flattening step linearly relative to the tool tool and the wafer in an in-plane direction parallel to the exposed surface. After the first tool cutting step of moving to and cutting the exposed surface with a tool, and after the first tool cutting step, the wafer is rotated by a predetermined angle around an axis perpendicular to the exposed surface. It is provided with a second tool cutting step in which the tool and the wafer are linearly and relatively moved in a direction parallel to the exposed surface in a plane, and the exposed surface is cut by the tool. A method for processing a wafer is provided.

In one aspect of the present invention, the predetermined angle for rotating the wafer in the second cutting tool cutting step may be 30 ° to 330 °. Further, the wafer may be a micro battery wafer.

In one aspect of the invention, a flattening step is performed to flatten the protective tape with a tool tool. Here, in the flattening step, the first cutting tool cutting step of cutting the protective tape with a tool tool and the protective tape being cut with a tool tool after rotating the wafer around an axis perpendicular to the exposed surface of the protective tape. A second tool cutting step is performed.

In the first tool cutting step, the tool and the wafer are linearly and relatively moved in a direction parallel to the exposed surface, and the exposed surface of the protective tape is cut by the tool. To do. Then, as the flattening of the protective tape progresses, rut-shaped cutting marks are formed on the protective tape.

In the second tool cutting step, the wafer is rotated by a predetermined angle around an axis perpendicular to the exposed surface of the protective tape, and then the protective tape is cut by a tool tool in the same manner as in the first tool cutting step. Then, the rotation direction of the tool wheel and the extension direction of the rut-shaped cutting mark do not match, so that the tool tool is less likely to be guided by the cutting mark. In the second cutting tool cutting step, the cutting marks formed in the first cutting tool cutting step are cut and removed, so that the cutting tool is less likely to be caught in the cutting marks.

Further, in the second cutting tool cutting step, a rut-shaped cutting mark is newly formed by cutting with a cutting tool, but the flattening step is divided into a first cutting tool cutting step and a second cutting tool cutting step. The cutting marks formed are shallower than in the case of carrying out without.

Therefore, in the wafer processing method according to one aspect of the present invention, the protective tape is difficult to peel off from the wafer. Then, since the protective tape is appropriately flattened, the wafer can be appropriately ground and then thinned.

Therefore, according to the present invention, there is provided a wafer processing method capable of suppressing peeling of the protective tape attached to the front surface side of the wafer and appropriately grinding the back surface side of the wafer.

FIG. 1 (A) is a schematic perspective view showing a step of attaching a protective tape, and FIG. 1 (B) is a schematic partial cross-sectional view showing an enlarged wafer having a protective tape attached to its surface. Is. FIG. 2A is a schematic side view showing the flattening step, and FIG. 2B is a schematic partial cross-sectional view showing the flattening step in an enlarged manner. FIG. 3A is a schematic top view showing a first cutting tool cutting step, and FIG. 3B is a schematic top view showing a second cutting tool cutting step. It is a perspective view which shows typically the grinding step.

Embodiments of the present invention will be described with reference to the accompanying drawings. First, a wafer which is a workpiece of the processing method according to the present embodiment will be described with reference to FIG. 1 (A). Wafer 1 is schematically shown on the lower side of FIG. 1 (A). The wafer 1 is, for example, a substantially disk-shaped substrate made of a material such as silicon, SiC (silicon carbide), or other semiconductor, or a material such as sapphire, glass, or quartz.

The surface 1a of the wafer 1 is divided into a plurality of regions by a plurality of scheduled division lines (streets) 3 arranged in a grid pattern, and each region partitioned by the plurality of scheduled division lines 3 is a device such as an IC. 5 is formed. Finally, the wafer 1 is thinned and split along the street 3 to form individual device chips. Further, a plurality of electrode bumps 7 serving as connection terminals for device chips are formed on the surface 1a of the wafer 1.

Next, the protective tape attached to the surface 1a of the wafer 1 will be described with reference to FIG. 1A. A protective tape 9 is schematically shown on the upper side of FIG. 1 (A). The protective tape 9 has a function of protecting the device 5 and the like formed on the surface 1a of the wafer 1. The protective tape 9 protects the surface 1a side of the wafer 1 from the impact applied during each step, transfer, etc. while the wafer processing method according to the present embodiment is being implemented, and prevents the device 5 from being damaged. To prevent.

The protective tape 9 is a flexible film-like base material 9a (see FIG. 1 (B)) and an adhesive layer 9b formed on one surface of the base material 9a (see FIG. 1 (B)). And have. For example, PO (polyolefin) is used for the base material 9a. PET (polyethylene terephthalate), polyvinyl chloride, polystyrene, etc., which have higher rigidity than PO, may be used. Further, for the adhesive layer 9b, for example, silicone rubber, acrylic material, epoxy material and the like are used.

Further, the protective tape 9 has a disk shape having a diameter smaller than the diameter of the wafer 1. The protective tape 9 is formed by cutting, for example, a strip-shaped protective tape sheet having a width larger than the diameter of the wafer 1. Alternatively, the protective tape sheet may be attached to the surface 1a of the wafer 1 and cut to have a predetermined shape while being attached to the surface 1a of the wafer 1.

Next, a method for processing the wafer 1 according to one aspect of the present invention will be described. The processing method of the wafer 1 is a step of attaching the protective tape 9 to the surface 1a of the wafer 1 and a flat surface by cutting the exposed surface (base material 9a side) of the protective tape 9 with a tool. A flattening step for flattening and a grinding step for grinding the back surface 1b side of the wafer 1 are provided. Hereinafter, each step of the wafer processing method will be described.

First, the step of attaching the protective tape will be described with reference to FIG. 1 (A). In the protective tape attaching step, the protective tape 9 is attached to the surface 1a of the wafer 1. When the protective tape 9 is attached to the surface 1a of the wafer 1, the adhesive layer 9b is directed toward the surface 1a of the wafer 1 and is attached so as not to protrude from the outer periphery of the wafer 1.

FIG. 1B is a schematic cross-sectional view showing an enlarged wafer 1 having a protective tape 9 attached to the surface 1a. As shown in FIG. 1B, the upper surface of the protective tape 9 has a shape having irregularities due to the electrode bumps 7 formed on the surface 1a of the wafer 1.

Therefore, when the wafer 1 is held on the chuck table 14 (see FIG. 4) of the grinding apparatus 12 described later via the protective tape 9 and the back surface 1b of the wafer 1 is ground, the height of the back surface 1b of the wafer 1 is increased. There is a problem that the processing accuracy is deteriorated due to the variation. Therefore, next, a flattening step of flattening the protective tape 9 is performed. FIG. 2A is a schematic side view for explaining the flattening step. The tool cutting device 2 shown in FIG. 2A is used for the flattening step.

The tool cutting device 2 has a chuck table 4. The chuck table 4 has a porous member (not shown) on the upper surface side. The upper surface of the porous member is a holding surface 4a for holding the work piece. The chuck table 4 includes a suction path (not shown) having one end connected to a suction source (not shown). The other end of the suction path is connected to the porous member. When the wafer 1 is placed on the holding surface 4a and the negative pressure generated by the suction source acts on the wafer 1 through the holes of the porous member, the wafer 1 is sucked and held by the chuck table 4.

The tool cutting device 2 further has a spindle 8, a tool wheel 6 held at one end of the spindle 8, and a tool tool 10 fixed to the tool wheel 6 above the chuck table 4. A rotary drive source (not shown) such as a motor is connected to the other end of the spindle 8, and the rotary drive source rotates the spindle 8.

The tool cutting device 2 further includes an elevating means (motor or the like) (not shown), and the elevating means can move the spindle 8 in the vertical direction. Further, a moving means (motor or the like) (not shown) is further provided, and the chuck table 4 can be linearly moved in a plane parallel to the holding surface 4a by the moving means. The chuck table 4 can rotate about an axis perpendicular to the holding surface 4a.

When the spindle 8 rotates, the tool wheel 6 to which the tool tool 10 is mounted rotates. Then, when the tool wheel 6 is lowered to a predetermined height position and the chuck table 4 is linearly moved so as to pass under the tool wheel 6, the tool tool 10 is attached to the surface 1a of the wafer 1. The protective tape 9 is cut by a tool when it hits the protective tape 9.

In the wafer processing method according to the present embodiment, the flattening step includes a first cutting tool cutting step and a second cutting tool cutting step. In the flattening step, first, the first cutting tool cutting step is carried out.

In the first cutting tool cutting step, the back surface 1b side of the wafer 1 is directed toward the holding surface 4a of the chuck table 4, the wafer 1 is placed on the holding surface 4a, and a negative pressure is applied from the chuck table 4 to the wafer 1. Then, the wafer 1 is attracted and held by the chuck table 4. Then, the base material 9a side of the protective tape 9 attached to the surface 1a of the wafer 1 is exposed upward.

Next, the spindle 8 of the tool cutting device 2 is rotated, the tool wheel 6 is rotated, and the tool wheel 6 is positioned at a height at which the tool tool 10 hits the protective tape 9. Then, when the chuck table 4 is linearly moved in the direction in the plane parallel to the holding surface 4a and the tool tool 10 hits the protective tape 9, the protective tape 9 is cut by the tool. FIG. 2B is a partial cross-sectional view schematically showing the positional relationship between the tool tool 10 at the time of cutting the tool, the wafer 1, and the protective tape 9.

When the chuck table 4 is linearly moved in a plane parallel to the holding surface 4a while rotating the bite wheel 6 around an axis perpendicular to the holding surface 4a, it is formed on the exposed surface of the protective tape 9. The convex portion of the uneven surface is cut by the tool tool 10. When the chuck table 4 is moved so as to pass under the bite wheel 6, the entire surface of the exposed surface of the protective tape 9 is cut with a bite. When this is repeated a plurality of times, the convex portion is removed and the exposed surface of the protective tape 9 is flattened.

However, by cutting the tool with the tool tool 10, rut-shaped cutting marks are formed on the exposed surface of the protective tape 9. The rut-shaped cutting marks have a shape along the rotation direction of the bite wheel 6. The rut-shaped cutting mark 11 will be described with reference to FIG. 3A.

FIG. 3A is a schematic top view showing the first cutting tool cutting step. FIG. 3A schematically shows a bite wheel 6, a chuck table 4, and a wafer 1. FIG. 3A shows a state after the chuck table 4 has passed the lower side of the bite wheel 6 in the first bite cutting step. As shown in FIG. 3A, rut-shaped cutting marks 11 are formed on the exposed surface of the protective tape 9.

In the wafer processing method according to the present embodiment, the second cutting tool cutting step is carried out after the first cutting tool cutting step. In the second cutting tool cutting step, first, the chuck table 4 is rotated by a predetermined angle around an axis perpendicular to the holding surface 4a. The predetermined angle is selected, for example, from the range of 30 ° to 330 °.

In the second cutting tool cutting step, the chuck table 4 is rotated around an axis perpendicular to the holding surface 4a, and then the chuck table 4 is passed under the bite wheel 6 to further expose the exposed surface of the protective tape 9. Bit cutting is performed to flatten the exposed surface of the protective tape 9.

In the second tool cutting step, the chuck table 4 is rotated and then the tool cutting is performed. Therefore, the tool tool 10 that rotates with the rotation of the tool wheel 6 has a rut shape formed in the first tool cutting step. It does not move along the cutting mark 11 of. Therefore, the tool tool 10 is not guided to the rut-shaped cutting mark 11 formed in the first tool cutting step.

In the second cutting step, the exposed surface of the protective tape 9 is cut and further flattened, and the rut-shaped cutting marks 11 formed in the first cutting step are also cut. On the other hand, in the second tool cutting step, a rut-shaped cutting mark 11 having a shape along the rotation direction of the tool tool in the second tool cutting step is newly formed. The rut-shaped cutting mark 11 will be described with reference to FIG. 3B.

FIG. 3B is a schematic top view showing a second cutting tool cutting step carried out by rotating the chuck table 4 by 180 °. FIG. 3B schematically shows a bite wheel 6, a chuck table 4, and a wafer 1. FIG. 3B shows a state after the chuck table 4 has passed the lower side of the bite wheel 6 in the second bite cutting step. The rut-shaped cutting marks 11 formed in the first cutting tool cutting step are partially removed and become shallower, while new rut-shaped cutting marks 11 are formed.

When the flattening step is carried out without dividing into the first cutting tool cutting step and the second cutting tool cutting step, when the protective tape 9 is repeatedly cut with a cutting tool, a deep rut is formed on the exposed surface of the protective tape 9. The shape of the cutting mark 11 is formed. When the rut-shaped cutting mark 11 formed on the protective tape 9 becomes deeper, the tool tool 10 is likely to be caught in the cutting mark 11, and the protective tape 9 is easily peeled off from the wafer 1.

On the other hand, in the wafer processing method according to the present embodiment, the flattening step is divided into a first cutting tool cutting step and a second cutting tool cutting step. The chuck table 4 is rotated when the second cutting tool cutting step is performed. Therefore, the rut-shaped cutting mark 11 finally formed becomes relatively shallow, and the tool tool 10 is less likely to be caught by the rut-shaped cutting mark 11. Therefore, according to the wafer processing method according to the present embodiment, the protective tape 9 is less likely to be peeled off in the flattening step.

For example, the exposed surface of the protective tape 9 attached to the surface 1a of the wafer 1 on which the plurality of electrode bumps 7 are formed on the surface 1a has irregularities with a height difference of about 20 μm. Therefore, the unevenness is removed by the flattening step to flatten the exposed surface of the protective tape 9.

For example, in the first cutting tool cutting step, the wafer 1 is passed through the lower side of the cutting tool wheel 6 three times, and the exposed surface side of the protective tape 9 is cut by 10 μm bite in the thickness direction. Then, in the second cutting tool cutting step, the chuck table 4 is rotated by 180 ° around an axis perpendicular to the holding surface 4a, and the wafer 1 is passed under the bite wheel 6 4 to 5 times to pass the protective tape 9 The exposed surface side of the is further cut by 10 μm bite in the thickness direction.

Next, the grinding step will be described with reference to FIG. FIG. 4 is a schematic perspective view for explaining the grinding step. In the grinding step, the wafer 1 is ground from the back surface 1b side to thin the wafer 1 to a predetermined thickness.

A grinding device for performing the grinding step will be described with reference to FIG. The grinding device 12 has a chuck table 14. The chuck table 14 has a porous member on the upper surface side. The upper surface of the porous member is a holding surface 14a for holding the work piece. The structure and function of the chuck table 14 are the same as those of the chuck table 4 of the cutting tool 2 described above.

The grinding device 12 further has a spindle 18, a grinding wheel 16 held at one end of the spindle 18, and a grinding wheel 20 fixed to the grinding wheel 16 above the chuck table 14. The other end of the spindle 18 is connected to a rotary drive source (motor), and in the grinding step, the rotary drive source rotates the spindle 18.

The grinding device 12 further includes an elevating means (motor) (not shown), and the elevating means can move the spindle 18 in the vertical direction. Further, a moving means (motor) (not shown) is further provided, and the chuck table 14 can be moved in a plane parallel to the holding surface 14a by the moving means. The chuck table 14 is rotatable about an axis perpendicular to the holding surface 14a.

When the spindle 18 rotates, the grinding wheel 16 on which the grinding wheel 20 is mounted rotates. Then, the grinding wheel 16 is lowered toward the wafer 1 held by the chuck table 14 by the elevating means, and when the grinding wheel 20 hits the back surface 1b of the wafer 1, the wafer 1 is ground. When the grinding wheel 20 is lowered to a predetermined height position, the wafer 1 is thinned to a predetermined thickness.

In the grinding step, first, the surface 1a side of the wafer 1 is directed toward the holding surface 14a of the chuck table 14, and the wafer 1 is positioned above the chuck table 14. Then, the wafer 1 is placed on the holding surface 14a via the protective tape 9, and a negative pressure is applied from the chuck table 14 to the wafer 1 to suck and hold the wafer 1 on the chuck table 14. Then, the back surface 1b side of the wafer 1 is exposed upward.

At this time, the wafer 1 is held on the chuck table 14 via the protective tape 9. In the wafer processing method according to the present embodiment, since the flattening step of flattening the protective tape 9 is performed before the grinding step, the surface of the protective tape 9 in contact with the chuck table 14 is flat. Therefore, the height of the back surface 1b of the wafer 1 held on the chuck table 14 does not vary.

Then, the chuck table 14 is rotated and the spindle 18 is rotated to rotate the grinding wheel 16, and the grinding wheel 16 is lowered toward the back surface 1b of the wafer 1 by the elevating means. When the grinding wheel 20 mounted on the rotating grinding wheel 16 comes into contact with the back surface 1b of the wafer 1, the wafer 1 is ground. Further, when the grinding wheel 16 is lowered to a predetermined height, the wafer 1 is thinned.

After that, when the thinned wafer 1 is divided along the scheduled division line 3, individual device chips are formed.

In the wafer processing method according to the present embodiment, the protective tape 9 is appropriately flattened in the flattening step without peeling from the wafer 1. Therefore, when the wafer 1 is held on the chuck table via the protective tape 9, the height of the exposed back surface 1b of the wafer 1 does not vary, and the back surface 1b of the wafer 1 is appropriately ground in the grinding step. Can be diluted.

The present invention is not limited to the description of the above embodiment, and can be implemented with various modifications. For example, when the wafer 1 is thinned, the strength of the wafer 1 is reduced, so that the wafer 1 is easily damaged. Therefore, in the grinding step, it is not necessary to grind only the back surface 1b corresponding to the device region in which the device 5 is formed, and not to grind the outer peripheral surplus region in which the device 5 is not formed on the front surface 1a of the wafer 1. At this time, the back surface 1b corresponding to the outer peripheral surplus region is not ground and becomes a remaining annular convex portion, and a concave portion is formed on the back surface 1b side of the wafer 1.

The structure, method, etc. according to the above embodiment can be appropriately modified and implemented as long as they do not deviate from the scope of the object of the present invention.

1 Wafer 1a Front surface 1b Back surface 3 Scheduled division line 5 Device 7 Electrode bump 9 Protective tape 9a Base material 9b Adhesive layer 11 Cutting mark 2 tool cutting device 4,14 Chuck table 4a, 14a Holding surface 6 tool cutting wheel 8,18 Spindle 10-bit tool 12 Grinding device 16 Grinding wheel 20 Grinding wheel

Claims (3)

This is a method for processing a wafer in which a plurality of scheduled division lines are set on the surface in a grid pattern and devices are formed in a plurality of regions partitioned by the plurality of scheduled division lines.
A protective tape attaching step of attaching a protective tape to the surface of the wafer, and
After the protective tape attaching step, a flattening step of cutting and flattening the exposed surface of the protective tape attached to the surface of the wafer with a tool tool,
After the flattening step, the front surface side of the wafer is directed toward the chuck table of the grinding device, the chuck table is held by the chuck table via the protective tape, and the back surface side of the wafer is ground to determine the wafer. With grinding steps to make the thickness of,
The flattening step is a first tool cutting in which the tool and the wafer are linearly and relatively moved in a direction parallel to the exposed surface in a plane, and the exposed surface is cut by the tool. After the step and the first tool cutting step, the tool is rotated by a predetermined angle around an axis perpendicular to the exposed surface to bring the tool and the wafer in-plane parallel to the exposed surface. A second tool cutting step in which the exposed surface is cut with a tool by moving it linearly and relatively in the direction of
A method for processing a wafer, which comprises. The wafer processing method according to claim 1, wherein a predetermined angle for rotating the wafer in the second cutting tool cutting step is 30 ° to 330 °. The wafer processing method according to claim 1, wherein the wafer is a micro-battery wafer.