Method for dividing a substrate

Abstract

To provide a method for reliably dividing a substrate by expansion of expanding tape.SOLUTION: A method includes: preparing a substrate 10 having a division starting point 15 along a predetermined dividing line, and a protective sheet 3 adhered to one side; applying an expanding tape 63 by rolling a roller on another side of the substrate 10; releasing suction by a holding table 51; rolling the roller 54 in contact with the expanding tape 63 while a slight gap 514 is formed between a holding surface 513 of the holding table 51 and the protective sheet 3; expanding a crack 16 extending from the division starting point 15 by sinking the substrate 10 through the protective sheet 3 into the gap 514 starting from the division starting point 15; expanding the expanding tape 63 to widen a chip interval starting at division starting point 15. Since the crack is expanded while sinking substrate 10 through the protective sheet 3 into the gap 514, the chip interval is reliably widened.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for dividing a substrate into a plurality of chips.

Background Art

[0002] As a method for dividing various substrates including semiconductor wafers, semiconductor package substrates, etc. into a plurality of individual chips, a method is known in which a laser beam is irradiated onto the substrate to form a modified layer as a starting point for division, an expandable tape is adhered to the substrate, and then the expandable tape is expanded to form a space between the chips (see, for example, Patent Document 1). When forming the modified layer, cracks continuous with the modified layer may be formed in the thickness direction of the substrate, and these cracks also serve as starting points for division.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, even when the expandable tape is expanded, an undivided region may occur in the planned division line. In particular, when the size of each individual chip is small, since the number of planned division lines is large, the expansion amount of each individual planned division line is not sufficient, and an undivided region is likely to occur.

[0005] The present invention has been conceived in view of such problems, and an object thereof is to ensure that the substrate can be divided by expanding the expandable tape.

Means for Solving the Problems

[0006] The present invention relates to a method for dividing a substrate into a plurality of chips along a planned division line, comprising: a substrate preparation step of preparing a substrate in which a division starting point is formed along the planned division line and a protective sheet is adhered to one surface; an expandable tape adhering step of rolling a roller on the other surface of the substrate to adhere an expandable tape while the protective sheet side is sucked and held by a holding table; a crack extension step of, after the expandable tape adhering step, releasing the suction by the holding table, bringing the roller into contact with the expandable tape and rolling it in a state where a slight gap is formed between the holding surface of the holding table and the protective sheet, and extending a crack extending from the division starting point while sinking the substrate into the gap through the protective sheet with the division starting point as a starting point; and a chip interval expansion step of, after the crack extension step, expanding the expandable tape to widen the intervals between the plurality of chips with the division starting point as a starting point. In this method for dividing a substrate, the substrate preparation step may include a modified layer forming step of irradiating a laser beam having a wavelength that is transmissive to the substrate with the condensing point positioned inside the substrate to form a modified layer serving as the division starting point inside the substrate, and a back surface grinding step of, after the modified layer forming step, adhering the protective sheet to the surface of the substrate and grinding the back surface side of the substrate.

Advantages of the Invention

[0007] In the present invention, before expanding the expand tape, in the crack extension step, while forming a slight gap between the holding surface of the holding table and the protective sheet, the roller is brought into contact with the expand tape and rolled, and starting from the splitting starting point, a crack extension step is performed in which a crack extending from the splitting starting point is extended while sinking the substrate into the gap through the protective sheet. Therefore, in the chip interval expansion step, the chip interval can be surely expanded. Accordingly, the generation of an unsplit region can be suppressed. Further, in the chip interval expansion step, since the crack extension step is performed using the step of attaching the expand tape, which was conventionally necessary, there is no need to introduce a new unit for extending the crack, such as transporting to another device and performing the crack extension step, and it can be efficiently performed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0009] 1 Substrate Preparation Step (1) Modified Layer Formation Step For example, the wafer 10 shown in FIG. 1 is a kind of substrate to which the present invention is applied, and its surface 11 is partitioned by a planned division line 13 and a plurality of devices 14 are formed thereon. As shown in FIG. 2, the back surface 12 side of the wafer 10 is held on the chuck table 21 of the laser processing apparatus 2, and while moving the chuck table 21 in the horizontal direction (the direction of arrow 210), a laser beam 221 having a wavelength that is transmissive to the wafer 10 is irradiated from the laser head 22 along the planned division line 13 shown in FIG. 1 with its focusing point positioned inside the wafer 10. Then, a modified layer 15 is formed along the planned division line 13. The modified layer 15 is formed in the same manner for other planned division lines 13, and when the modified layers 15 are formed vertically and horizontally for all the planned division lines 13, the modified layer formation step is completed. The modified layer 15 serves as a starting point for dividing the wafer 10 into individual devices 14 later.

[0010] (2) Back surface grinding step Next, as shown in FIG. 3, a protective sheet 3 is attached to the surface 11 of the wafer 10, and the protective sheet 3 side is held on the chuck table 41 of the grinding apparatus 4. The chuck table 41 is rotatable about a vertical rotation axis 410. Further, this grinding apparatus 4 includes a grinding wheel 42 having a grinding stone 422 fixed in an annular shape to the lower surface of a base 421 and rotatable about a vertical rotation axis 420. The chuck table 41 is rotated about the rotation axis 410, and the grinding wheel 42 rotating about the rotation axis 420 is lowered to bring the rotating grinding stone 422 into contact with the back surface 12 of the wafer 10. Then, when the wafer 10 is formed to a predetermined thickness, the back surface grinding step is completed.

[0011] 2 Expand tape attachment step After the substrate preparation step, the wafer 10 with the protective sheet 3 attached to the surface 11 is transported to the tape attaching device 5 shown in FIG. 4, and the protective sheet 3 side is held on the holding table 51 of the tape attaching device 5. This holding table 51 includes a porous member 511, and the porous member 511 is connected to a suction source 53 via a valve 52. The porous member 511 is supported from below and laterally by a frame body 512. The upper surface of the porous member 511 serves as a holding surface 513 for holding the wafer 10.

[0012] In this step, the wafer 10 is placed on the holding surface 513 of the holding table 51 with the protective sheet 3 side facing down. Also, a ring frame 61 is placed on the frame body 512. Then, the valve 52 is opened to communicate the porous member 511 with the suction source 53, and the wafer 10 is suction-held via the protective sheet 3 on the holding surface 513 which is the upper surface of the porous member 511. In the expand tape attaching step, it is necessary to perform suction holding because if the wafer 10 is not fixed, bubbles or wrinkles may enter the expand tape.

[0013] Next, a DAF (die attach film) 62 is attached to the back surface 12 of the wafer 10, and an expand tape 62 is placed on the DAF 62 and the ring frame 61. Then, while pressing the roller 54 downward and rolling it in the direction of arrow 540, the expand tape 63 is attached to the back surface 12 of the wafer 10 via the DAF 62 and also to the upper surface of the ring frame 61. In this way, the wafer 10 is in a state where the expand tape 63 is attached to the back surface 12 side and is supported by the ring frame 61.

[0014] Note that the holding table 51 of the tape attaching device 5 shown in FIG. 4 is configured to suction-hold the wafer 10 by the suction force acting on the porous member 511. However, instead of the porous member 511, a table having suction grooves formed on its surface may be used, and the wafer 10 may be suction-held by the suction force acting on the suction grooves.

[0015] 3 Crack Extension Step After performing the step of attaching the expand tape, as shown in FIG. 5, by closing the valve 52, the suction in the porous member 511 is released. Then, a slight gap 514 is formed between the holding surface 513 and the protective sheet 3. With the gap 514 formed in this way, the roller 54 is brought into contact with the expand tape 63 and rolled in the direction of arrow 541 while being pressed downward. Then, starting from the modified layer 15 which is the starting point of division, the wafer 10 sinks into the gap 514 through the protective sheet 3, and thereby a crack 16 starting from the modified layer 15 which is the starting point of division is formed in the wafer 10 in the thickness direction, and this crack 16 can be extended toward the front and back surfaces. Although no crack is formed in FIG. 5, a crack may already have been formed in any of the steps before the crack extension step, and it may be further extended in the crack extension step. If there is no protective sheet 3 and the wafer 10 is simply pressed directly against the holding surface 513 of the holding table 51, since the holding surface 513 is hard, the wafer 10 being pressed by the sticking roller 54 cannot sink in, and the crack cannot extend. However, if the protective sheet 3 containing resin is interposed between the holding surface 513, the holding sheet 3 has a predetermined thickness and deforms when pressed. Therefore, when pressed by the sticking roller 54, the wafer 10 crushes the protective sheet 3, and the chips formed starting from the division starting point sink in an inclined manner with respect to the holding surface 513, and the crack can be extended. However, if the thickness of the protective sheet 3 is not sufficient, or if the material of the protective sheet 3 is hard and the amount of deformation is small, it cannot be crushed even when pressed. In the case of such a protective sheet 3, when the protective sheet 3 is adsorbed to the holding surface 513, the wafer 10 cannot sink in sufficiently. Therefore, in the present invention, the suction in the porous member 511 is further released to form a slight gap 514 between the holding surface 513 and the protective sheet 3, and by sinking the protective sheet 3 into the gap 514 by the pressing of the sticking roller 54, when pressed by the sticking roller 54, in addition to the amount by which the wafer 10 crushes and sinks the holding sheet 3, it becomes possible to sink into the gap 514 also through the holding sheet 3, and the crack 16 can be efficiently extended. By extending the crack 16 in the thickness direction of the wafer 10, the wafer 10 is divided along the division planned line 13. Even if there is a division planned line 13 that is not divided, by extending the crack 16, it becomes possible to divide smoothly in the subsequent chip interval expansion step. In the present embodiment, since the crack 16 is extended using the expand tape sticking step that has been conventionally performed, it can be carried out without the need to transfer to a separate device or add a new drive unit for crack extension to the existing device, preventing a significant decrease in productivity. Also, since the protective sheet 3 used in the grinding step is used as it is in the crack extension step, there is no need to newly stick it for the crack extension step, which is efficient. Further, by setting the direction of arrow 541 to be opposite to the direction of arrow 540 in the expand tape attaching step, the roller 54 is reciprocated once, so that the expand tape attaching step and the crack extension step can be carried out efficiently.

[0016] 4 Chip Interval Expansion Step After the crack extension step is carried out, the wafer 10 supported by the ring frame 61 via the expand tape 63 is conveyed to the tape expansion device 7 shown in FIG. 6. This tape expansion device 7 includes a frame mounting table 71 on which the ring frame 61 is placed, a fixing portion 72 that presses and fixes the ring frame 61 from above, a lifting mechanism 73 that raises and lowers the frame mounting table 71 and the fixing portion 72, a drum 74 that is disposed on the inner peripheral side of the frame mounting table 71 and the fixing portion 72 and is formed in a cylindrical shape, and a plurality of rollers 75 that are disposed at the upper end of the drum 74.

[0017] The ring frame 61 is placed on the frame mounting table 71. At this time, the frame mounting table 71 is located at substantially the same height position as the rollers 75. Also, the ring frame 61 is sandwiched between the fixing portion 72 and the frame mounting table 71. The expand tape 63 is supported from below by the rollers 75 at a position on the inner peripheral side of the frame mounting table 71 and on the outer peripheral side of the wafer 10.

[0018] From this state, the lifting mechanism 73 lowers the frame mounting table 71 and the fixing portion 72. Then, while all the rollers 75 rotate in the radial direction passing through the center of the drum 74, the expand tape 63 is radially expanded. Then, with respect to the division planned line 13 that was not divided in the crack extension step, it is divided starting from the modified layer 15 and the crack 16 that are the division starting points, and the division groove 17 shown in FIG. 7 is formed and divided into a plurality of chips for each individual device 14, and further, the interval (chip interval) between adjacent chips is widened. On the other hand, with respect to the division planned line 13 that has already been divided into chips in the crack extension step, the chip interval is further widened.

[0019] As described above, in the crack extension step, with a slight gap 514 formed between the holding surface 513 and the protective sheet 3, the roller 54 is brought into contact with the expandable tape 63 and rolled while being pressed downward, and the wafer 10 is sunk into the gap 514 through the protective sheet 3 starting from the modified layer 15 to form a crack 16 starting from the modified layer 15 which is the splitting starting point. Thus, in the chip interval expansion step, the chip interval can be surely expanded. Therefore, the possibility of an unsplit region occurring in the planned splitting line 13 can be reduced.

[0020] Note that in the substrate preparation step in the above embodiment, after forming the modified layer 15 inside the wafer 10, the protective sheet 3 is adhered to the surface 11 of the wafer 10, the protective - sheet - 3 side is held on the chuck table 41 of the grinding device 4, and in that state, the back surface 12 of the wafer 10 is ground to form the wafer 10 to a predetermined thickness. However, it may be carried out according to the following procedure. (A) The protective sheet 3 is adhered to the surface 11 of the wafer 10, the protective - sheet - 3 side is held on the chuck table 41 of the grinding device 4, and in that state, the back surface 12 of the wafer 10 is ground to form the wafer 10 to a predetermined thickness. Then, a laser beam is incident from the back - surface 12 side to form a modified layer inside. In this case, the protective sheet 3 adhered to the surface 11 during the grinding of the back surface 12 of the wafer 10 can be used as it is as the protective sheet 3 into which the substrate sinks in the subsequent crack extension step. There is no need to adhere the protective sheet 3 for the crack extension step, which is efficient. (a) Attach the protective sheet 3 to the surface of the wafer 10, hold the protective sheet 3 side on the chuck table 41 of the grinding device 4, and in this state, grind the back surface 12 of the wafer 10 to form the wafer 10 to a predetermined thickness. Then, irradiate a laser beam through the protective sheet 3 from the surface 11 side of the wafer 10 to form a modified layer inside the wafer 10. In this case, the protective sheet 3 attached to the surface 11 during the grinding of the back surface 12 of the wafer 10 can be used as it is as the protective sheet 3 on which the substrate sinks in the subsequent crack extension step, eliminating the need to attach the protective sheet 3 for the crack extension step, which is efficient. (c) With the back surface 12 side of the wafer 10 held on the chuck table 41 of the laser processing device, irradiate a laser beam from the surface 11 side to form a modified layer inside the wafer 10, and then attach the protective sheet 3 to the surface 11. This is the case when grinding of the back surface 12 is not required.

[0021] In the substrate preparation step of this embodiment, a modified layer is formed inside the substrate in the modified layer formation step. However, instead of the modified layer formation step, an ablation processing step of condensing a laser beam on the surface of the substrate to perform ablation processing may be implemented. In this case, in the crack extension step, starting from the processing groove formed by the ablation processing, the wafer 10 can sink into the gap 514 through the protective sheet 3, and the crack can be extended toward the back surface of the substrate.

Explanation of Signs

[0022] 10: Wafer 11: Surface 12: Back surface 13: Division planned line 14: Device 15: Modified layer 16: Crack 17: Division groove 2: Laser processing device 21: Chuck table 22: Laser head 221: Laser beam 3: Protective sheet 4: Grinding device 41: Chuck table 410: Rotation axis 42: Grinding wheel 420: Rotation axis 421: Base 422: Grinding stone 5: Tape sticking device 51: Holding table 511: Porous member 512: Frame 513: Holding surface 514: Gap 52: Valve 53: Suction source 54: Roller 61: Ring frame 62: Expandable tape 7: Tape expansion device 71: Frame mounting table 72: Fixed part 73: Lifting mechanism 74: Drum 75: Roller

Claims

1. A method for dividing a substrate into a plurality of chips along a planned division line, comprising: a substrate preparation step of preparing a substrate having a division starting point formed along the planned division line and a protective sheet adhered to one surface thereof; an expandable tape adhering step of rolling a roller on the other surface of the substrate to adhere an expandable tape while sucking and holding the protective sheet side on a holding table; after the expandable tape adhering step is performed, releasing the suction by the holding table, bringing the roller into contact with the expandable tape and rolling it in a state where a slight gap is formed between the holding surface of the holding table and the protective sheet, and extending a crack extending from the division starting point while sinking the substrate into the gap through the protective sheet starting from the division starting point; after the crack extension step is performed, expanding the expandable tape to widen the intervals between the plurality of chips starting from the division starting point. The method for dividing a substrate is characterized by comprising the above steps. The method for dividing a substrate.

2. The substrate preparation step includes: a modified layer forming step of irradiating a laser beam having a wavelength that is transmissive to the substrate with the condensing point positioned inside the substrate to form a modified layer serving as the division starting point inside the substrate; after the modified layer forming step is performed, adhering the protective sheet to the surface of the substrate and grinding the back surface side of the substrate. The method for dividing a substrate according to claim 1 is characterized by comprising the above steps. having the above steps. The method for dividing a substrate according to claim 1.

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