KR102680920B1 - Method for cutting workpiece - Google Patents

Abstract

The purpose of the present invention is to provide a cutting method for a workpiece that can efficiently suppress the generation of burrs in a die attach film while preventing the occurrence of machining defects in the workpiece.
A cutting method of cutting a plate-shaped workpiece with a cutting blade, each of which has a device formed in a surface area divided by a plurality of division lines formed in a grid, wherein a die attach film and a dicing tape are laminated. In addition to adhering the die attach film of the laminated tape to the back side of the workpiece, attaching the outer peripheral portion of the dicing tape to an annular frame to form a frame unit, and passing the workpiece through the laminated tape to the chuck table of the cutting device maintaining the workpiece, forming a cutting groove for cutting the workpiece by downcut along the line to be divided, and cutting the die attach film exposed at the bottom of the cutting groove by upcut with a cutting blade. Equipped with

Description

Method for cutting workpieces {METHOD FOR CUTTING WORKPIECE}

The present invention relates to a cutting method for cutting a plate-shaped workpiece with a cutting blade.

A plate-shaped workpiece, such as a semiconductor wafer or glass substrate, on which a plurality of devices represented by ICs (Integrated Circuits), etc. are formed on the surface, is divided along a dividing line (street) to form a plurality of device chips each containing a device. This is obtained. This division of the workpiece is performed, for example, using a cutting device equipped with an annular cutting blade for cutting the workpiece. By rotating the cutting blade and cutting into the workpiece along the dividing line, the workpiece is cut and divided.

A die bonding adhesive layer called a die attach film is often attached to each device chip. Regarding the adhesion of the die attach film, first, a die attach film covering the entire back surface of the workpiece is adhered to the workpiece before division, and then the workpiece is divided for each die attach film along the dividing line, A method of obtaining a plurality of device chips with die attach films attached is known.

Since the die attach film is formed of a flexible resin, etc., when the die attach film is cut with a cutting blade, the die attach film is stretched by the cutting blade, and whisker-like protrusions (burrs) are generated. Since this burr can become an obstacle when die bonding a device chip, various proposals have been made for suppressing the burr. For example, Patent Document 1 discloses a method of shrinking burrs by cutting the die attach film with a cutting blade and then subjecting the die attach film to a heat treatment.

[Patent Document 1] Japanese Patent Publication No. 2004-79597

As described above, when the flexible die attach film is attached to the back side of the workpiece, the workpiece is supported by the flexible member. In this state, if the workpiece and the die attach film are cut simultaneously with a cutting blade, processing defects such as chips or cracks may occur in the workpiece.

Additionally, regarding the burrs generated when the die attach film is cut with a cutting blade, a method of shrinking the burrs by heating as described above has been proposed. However, this method requires an independent heat treatment process separate from the division of the workpiece to remove the burrs, which reduces the production efficiency of device chips.

The present invention was made in view of these problems, and its object is to provide a cutting method for a workpiece that can efficiently suppress the generation of burrs in a die attach film while preventing the occurrence of machining defects in the workpiece.

According to the present invention, there is provided a cutting method for cutting a plate-shaped workpiece with a cutting blade, each of which has a device formed on a surface side area divided by a plurality of division lines formed in a grid, wherein the die attach film and the die are cut. A frame unit forming step of adhering the die attach film of the laminated tape on which the dicing tape is laminated to the back surface of the workpiece, and adhering the outer peripheral portion of the dicing tape to an annular frame to form a frame unit, A holding step of holding a workpiece to a chuck table of a cutting device through the laminated tape, wherein the chuck table and the cutting blade are aligned so that the moving direction of the rotating lower end of the cutting blade coincides with the moving direction of the chuck table. a first cutting step of forming a cutting groove for cutting the workpiece while leaving the die attach film along the division line by relatively moving the cutting blade to cut into the workpiece; After performing the cutting step, the chuck table and the cutting blade are relatively moved so that the direction in which the lower end of the rotating cutting blade moves and the moving direction of the chuck table are opposite to the direction in which the lower end of the rotating cutting blade moves, so that the chuck table is exposed at the bottom of the cutting groove. A method of cutting a workpiece including a second cutting step of cutting the die attach film with the cutting blade is provided.

Additionally, in the method of cutting a workpiece according to the present invention, the depth at which the cutting blade cuts into the die attach film in the first cutting step may be 5 μm or less.

In the method of cutting a workpiece according to the present invention, the workpiece adhered on the die attach film is cut by downcut, and then the die attach film is cut by upcut. As a result, the occurrence of processing defects (chipping, cracks, etc.) of the workpiece can be prevented, and the occurrence of burrs in the die attach film can be efficiently suppressed.

Figure 1 is a perspective view showing an example of the configuration of a frame unit.
Figure 2 is a partial cross-sectional side view showing a state in which a workpiece is held by a chuck table of a cutting device.
Figure 3 (A) is a partial cross-sectional side view showing the cutting groove being formed, and Figure 3 (B) is an enlarged view of the lower end of the cutting blade in the first cutting step.
Figure 4 is a partial cross-sectional side view showing the machining feed in the first cutting step.
Figure 5 (A) is a partial cross-sectional side view showing the die attach film being cut, and Figure 5 (B) is an enlarged view of the lower end of the cutting blade in the second cutting step.
Figure 6 is a partial cross-sectional side view showing the machining feed in the second cutting step.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is a perspective view showing a configuration example of a frame unit 11 in which a plate-shaped workpiece 13 is supported by an annular frame 19 according to the present embodiment.

The workpiece 13 is formed in a disk shape using a semiconductor wafer, a glass substrate, etc., and has a front surface 13a and a back surface 13b. The workpiece 13 is divided into a plurality of regions by a plurality of division lines (streets) 15 arranged in a grid, and on the surface 13a side of the plurality of regions, devices each composed of ICs, etc. 17) has been formed. By dividing the workpiece 13 along the division line 15, a plurality of device chips each including a device 17 are obtained.

Additionally, there are no restrictions on the material, shape, structure, size, etc. of the workpiece 13. For example, as the workpiece 13, a semiconductor substrate (silicon substrate, SiC substrate, GaAs substrate, InP substrate, GaN substrate, etc.), a glass substrate, a sapphire substrate, a ceramic substrate, a resin substrate, a metal substrate, etc. can be used. Additionally, there are no restrictions on the type, quantity, shape, structure, size, arrangement, etc. of the devices 17.

When dividing the workpiece 13, first, a frame unit 11 in which the workpiece 13 is supported by the annular frame 19 is formed to hold the workpiece 13 by the chuck table of the processing device. (frame unit formation step).

As shown in FIG. 1, the workpiece 13 is attached to the annular frame 19 through a laminated tape 21 in which a circular die attach film 23 and a circular dicing tape 25 are laminated. It is supported. The laminated tape 21 is constructed by adhering a flexible die attach film 23 onto the dicing tape 25, and the die attach film 23 has a diameter equal to or greater than the diameter of the workpiece 13. It is formed to be less than or equal to the diameter of the dicing tape 25.

The die attach film 23 of the laminated tape 21 is adhered to the back surface 13b of the workpiece 13, and the outer peripheral portion of the dicing tape 25 is adhered to the annular frame 19. As a result, the frame unit 11 in which the workpiece 13 is supported by the annular frame 19 is obtained.

Additionally, there are no restrictions on the materials of the die attach film 23 and the dicing tape 25. For example, the die attach film 23 can be formed of acrylic and epoxy resin, and the dicing tape 25 can be formed of resin such as polyolefin or vinyl chloride.

Next, the workpiece 13 supported by the annular frame 19 is held by the chuck table of the cutting device via the laminated tape 21 (holding step). Figure 2 is a partial cross-sectional side view showing a state in which the workpiece 13 is held by the chuck table 4 of the cutting device 2.

The cutting device 2 is provided with a chuck table 4 that suction-holds the workpiece 13 and a clamp 8 that fixes an annular frame 19 that supports the workpiece 13. The workpiece 13 is placed on the chuck table 4 through the laminated tape 21, and the annular frame 19 is fixed by the clamp 8. A part of the upper surface of the chuck table 4 constitutes a holding surface 4a that suctions and holds the workpiece 13 through the laminated tape 21, and this holding surface 4a is inside the chuck table 4. It is connected to a suction source (not shown) through a suction path (not shown) formed in .

Additionally, a machining transfer mechanism (not shown) is installed below the chuck table 4. This machining feed mechanism has a function of moving the chuck table 4 in the machining feed direction (first horizontal direction) substantially parallel to the holding surface 4a. Additionally, instead of the chuck table 4, a chuck table that holds the workpiece 13 by mechanical or electrical methods may be used.

Additionally, the cutting device 2 is provided with a cutting unit 6 for cutting the workpiece 13 above the chuck table 4. The cutting unit 6 is provided with a spindle 10 whose axis is located in a direction substantially parallel to the holding surface 4a, and an annular cutting blade 12 is mounted on the distal end of the spindle 10. The spindle 10 is connected to a rotational drive source (not shown) such as a motor, and the cutting blade 12 mounted on the spindle 10 rotates by force transmitted from the rotational drive source. The cutting blade 12 is made of, for example, an electrophoretic grindstone in which diamond abrasive grains are fixed with nickel plating.

Additionally, the cutting unit 6 is supported by a lifting mechanism (not shown) and an indexing transfer mechanism (not shown). The lifting mechanism has a function of moving (elevating) the cutting unit 6 in the cutting feed direction (vertical direction), and the indexing feeding mechanism moves the cutting unit 6 approximately parallel to the holding surface 4a and the machining feed direction ( It has a function of moving in an indexing transfer direction (second horizontal direction) that is approximately perpendicular to the first horizontal direction.

In the holding step, the workpiece 13 is placed on the holding surface 4a of the chuck table 4 through the laminated tape 21, and the annular frame 19 is held fixed by the clamp 8. Negative pressure from the suction source is applied to the surface 4a. Thereby, the workpiece 13 is held by the chuck table 4 via the laminated tape 21 with the surface 13a side exposed upward.

Next, by cutting the cutting blade 12 into the workpiece 13, a cutting groove 27 for cutting the workpiece 13 while leaving the die attach film 23 is formed along the division line 15. (first cutting step). Figure 3 (A) is a partial cross-sectional side view showing the cutting groove 27 being formed in the first cutting step.

In the first cutting step, the cutting blade 12 is rotated to cut into the workpiece 13, while the chuck table 4 is moved in a direction approximately parallel to the holding surface 4a and approximately perpendicular to the axis center of the spindle 8. Processing transfer is performed to move relatively. As a result, a straight cutting groove 27 for cutting the workpiece 13 is formed.

The height of the cutting blade 12 in the vertical direction in the first cutting step is set so that the workpiece 13 is cut and the die attach film 23 is not cut. FIG. 3(B) is an enlarged view of the lower end of the cutting blade 12 in the first cutting step. As shown in (B) of FIG. 3, the cutting blade 12 is positioned so that its lower end is approximately at the same height as the back surface 13b of the workpiece 13.

In this state, by performing a machining feed that relatively moves the chuck table 4 and the cutting blade 12, the cutting blade 12 cuts the workpiece 13 without cutting the die attach film 23. do. As a result, the die attach film 23 is exposed at the bottom of the cutting groove 27 formed by the cutting blade 12.

As such, in the first cutting step, the height of the cutting blade 12 is set so that the cutting blade 12 does not cut into the die attach film 23, and only the workpiece 13 is cut by the cutting blade 12. do. This avoids the occurrence of processing defects (chipping, cracks, etc. on the back side 13b) of the workpiece 13 that may occur when the workpiece 13 and the die attach film 23 are cut at the same time. can do.

Additionally, the height of the cutting blade 12 may be set so that the cutting blade 12 is slightly incised into the die attach film 23. If the cutting depth of the cutting blade 12 into the die attach film 23 is less than the thickness of the die attach film 23, the die attach film 23 remains without being cut. However, if the depth at which the cutting blade 12 is cut into the die attach film 23 increases, processing defects are likely to occur, so it is preferable that the cut depth is, for example, 5 μm or less.

In addition, in the first cutting step, the chuck table 4 and the cutting blade 12 are relatively moved so that the direction in which the lower end of the rotating cutting blade 12 moves and the moving direction of the chuck table 4 match. Perform transfer.

Figure 4 is a partial cross-sectional side view showing the machining feed in the first cutting step. As shown in FIG. 4, the cutting blade 12 is rotated in the direction indicated by arrow A, and the chuck table 4 is moved in the machining feed direction indicated by arrow B. As a result, a so-called downcut is performed in which the cutting blade 12 cuts the workpiece 13 from the front surface 13a side of the workpiece 13 toward the back side 13b.

When cutting the workpiece 13 in which the surface 13a is exposed and the back surface 13b is supported by a support member (the die attach film 23 in FIG. 4), the cutting blade 12 cuts the back surface 13b. When a so-called upcut is performed to cut the workpiece 13 from the ) side toward the surface 13a, chipping is likely to occur on the surface 13a side. On the other hand, when cutting the workpiece 13b by downcut, the occurrence of chipping tends to be suppressed by the support member supporting the back surface 13b side.

Therefore, in this embodiment, the workpiece 13 is cut by downcut. As a result, the occurrence of chipping when dividing the workpiece 13 can be suppressed.

As described above, in the first cutting step, the workpiece 13 is cut by downcut under the condition that the cutting blade 12 does not cut into the die attach film 23 or the cutting amount is small. As a result, the occurrence of processing defects due to cutting of the workpiece 13 can be suppressed.

Next, the die attach film 23 exposed at the bottom of the cutting groove 27 formed in the first cutting step is cut with the cutting blade 12 (second cutting step). Figure 5 (A) is a partial cross-sectional side view showing the die attach film 23 being cut in the second cutting step.

In the second cutting step, the cutting blade 12 is rotated to cut into the die attach film 23 exposed at the bottom of the cutting groove 27, while the chuck table 4 is held approximately parallel to the holding surface 4a. Machining transfer is performed by moving the spindle 8 in a direction approximately perpendicular to its axis. Thereby, the die attach film 23 is cut along the cutting groove 27.

The vertical height of the cutting blade 12 in the second cutting step is set so that the die attach film 23 is cut. FIG. 5(B) is an enlarged view of the lower end of the cutting blade 12 in the second cutting step. As shown in Figure 5 (B), the lower end of the cutting blade 12 is disposed below the lower surface of the die attach film 23, and is capable of cutting the entire thickness direction of the die attach film 23. It is positioned so that

By carrying out processing in this state, the cutting blade 12 cuts the die attach film 23 along the cutting groove 27. However, in the second cutting step, unlike the first cutting step, the direction in which the lower end of the rotating cutting blade 12 moves and the direction in which the chuck table 4 moves is different. Move it relatively in the reverse direction.

Figure 6 is a partial cross-sectional side view showing the machining feed in the second cutting step. As shown in FIG. 6, the cutting blade 12 is rotated in the direction indicated by arrow A, and the chuck table 4 is moved in the machining feed direction indicated by arrow C. As a result, an upcut is performed in which the cutting blade 12 cuts the die attach film 23 from the lower surface toward the upper surface.

When cutting the die attach film 23 with the cutting blade 12, the die attach film 23 may be stretched by the cutting blade 12, resulting in whisker-shaped protrusions (burrs). Since this burr may become an obstacle when die bonding the device chip obtained by dividing the workpiece 13, it is desirable to avoid generating it as much as possible.

As shown in FIG. 6, when the upper surface side of the die attach film 23 is covered with the workpiece 13, and the lower side side is covered with the dicing tape 25 that is softer than the workpiece 13, When the die attach film 23 is cut in a downcut manner as in the first cutting step, the die attach film 23 is cut toward the more flexible dicing tape 25 side. In this way, when the cutting blade 12 cuts the die attach film 23 toward the flexible layer, burrs in the die attach film 23 tend to occur.

Therefore, in this embodiment, the die attach film 23 is cut by upcutting, and the die attach film 23 is cut toward the workpiece 13, which has higher rigidity than the dicing tape 25. Accordingly, the generation of burrs due to cutting of the die attach film 23 is suppressed.

Additionally, the first cutting step and the second cutting step can be performed continuously on the outgoing and return paths of the machining transfer, respectively. Specifically, first, the chuck table 4 is moved (outbound) in the first machining feed direction indicated by arrow B (FIG. 4), so that the workpiece 13 is cut by downcut. Thereafter, without changing the rotation direction of the cutting blade 12, the chuck table is moved (backtrack) in the second machining feed direction indicated by arrow C (FIG. 6), that is, in the opposite direction to the first machining feed direction, thereby attaching the die. The film 23 is cut with an upcut.

In this way, the second cutting step of cutting the die attach film 23 by upcut can be performed continuously by changing the moving direction of the chuck table 4 after the first cutting step. Therefore, the generation of burrs in the die attach film 23 can be efficiently suppressed without adding a new independent process such as heat treatment.

Additionally, the second cutting step can be performed without moving the spindle 10 of the cutting unit 6 in the indexing transfer direction after the first cutting step. Therefore, positional deviation of the cutting area of the cutting blade 12 does not occur in the first cutting step and the second cutting step, and it is possible to prevent the workpiece 13 from being cut with an upcut in the second cutting step. Thereby, it is possible to avoid chipping occurring on the surface 13a side of the workpiece 13.

When the first cutting step and the second cutting step are performed on all the division lines 15, the workpiece 13 is divided into a plurality of device chips equipped with devices 17 and attached to a die attach film. As a result, a high-quality device chip with suppressed processing defects (chipping, cracks, etc.) and burrs in the die attach film is obtained.

The results of cutting the workpiece 13 and the die attach film 23 by the first cutting step and the second cutting step are shown in Table 1. Table 1 shows the depth at which the cutting blade 12 is cut into the die attach film 23 in the first cutting step, set to -5 ㎛, 0 ㎛, 5 ㎛, and 10 ㎛, and the chipping and die of the obtained device chip. This shows the presence or absence of burrs in the attach film 23. Additionally, the die attach film 23 was used with a thickness of 30 μm.

In addition, the cutting depth of -5 μm is a condition in which the lower end of the cutting blade 12 is located 5 μm above the back surface 13b of the workpiece 13. In addition, the cutting depth of 0 ㎛ is such that the cutting blade 12 is positioned so that the lower end of the cutting blade 12 and the back surface 13b of the workpiece 13 are at the same height, and the die attach film of the cutting blade 12 This is a condition where there is no infeed to (23).

From Table 1, the first cutting step was performed under the condition that the cutting depth was -5 ㎛, that is, a part of the back side 13b of the workpiece 13 was not cut, and the workpiece 13 was not completely cut. In this case, it can be seen that chipping is occurring in the device chip. Therefore, in the first cutting step, it is desirable to set the cutting depth to 0 μm or more so that at least the workpiece 13 can be cut.

It can be seen that when the cutting depth is 0 μm or more and 5 μm or less, chipping of the device chip does not occur and good results are obtained. On the other hand, when the cutting depth reached 10 ㎛, chipping occurred in the device chip. Therefore, it is particularly preferable that the depth of cut of the cutting blade 12 into the die attach film 23 in the first cutting step is 5 μm or less. However, if the frequency of occurrence of chipping is below a certain level, the first cutting step may be performed with the cutting depth set to greater than 5 ㎛.

Additionally, no burrs in the die attach film 23 were observed no matter what the cutting depth was. Therefore, it can be seen that even if the die attach film 23 is cut to some extent in the first cutting step, the generation of burrs can be prevented by cutting the die attach film 23 with an upcut in the second cutting step. .

As described above, in the processing method of the workpiece according to the present embodiment, the workpiece 13 adhered on the die attach film 23 is cut by downcut, and then the die attach film 23 is cut by upcut. cut by As a result, the occurrence of machining defects (chipping, cracks, etc.) of the workpiece 13 can be prevented, and the occurrence of burrs in the die attach film 23 can be efficiently suppressed.

In addition, the structure, method, etc. according to the above embodiments can be implemented with appropriate changes as long as they do not deviate from the scope of the purpose of the present invention.

11: frame unit 13: workpiece
13a: Surface 13b: Back side
15: Line to be divided 17: Device
19: Annular frame 21: Laminated tape
23: Die attach film 25: Dicing tape
27: cutting groove 2: cutting device
4: Chuck table 4a: Holding surface
6: cutting unit 8: clamp
10: spindle 12: cutting blade

Claims (2)

A method of cutting a plate-shaped workpiece with a cutting blade, each of which has a device formed in a surface area divided by a plurality of division lines formed in a grid, comprising:
Forming a frame unit by attaching the die attach film of a laminated tape in which a die attach film and a dicing tape are laminated to the back surface of the workpiece, and attaching the outer peripheral portion of the dicing tape to a circular frame to form a frame unit. steps,
a holding step of holding the workpiece to a chuck table of a cutting device through the laminated tape;
The chuck table and the cutting blade are relatively moved so that the moving direction of the lower end of the rotating cutting blade matches the moving direction of the chuck table, and the cutting blade is cut into the workpiece, thereby attaching the die. A first cutting step of forming a cutting groove for cutting the workpiece while leaving a film along the division line,
After performing the first cutting step, the chuck table and the cutting blade are relatively moved so that the direction in which the lower end of the rotating cutting blade moves and the moving direction of the chuck table are opposite to the first cutting step. A method of cutting a workpiece, comprising a second cutting step of cutting the die attach film exposed at the bottom of the cutting groove with the cutting blade. The method of claim 1, wherein in the first cutting step, a depth at which the cutting blade is cut into the die attach film is 5 μm or less.