JP6295154B2 - Wafer dividing method - Google Patents

Description

  The present invention relates to a dividing method for dividing a wafer into individual chips.

  A wafer on which a device such as an IC or LSI is partitioned by a predetermined division line and formed on the surface is divided into individual chips having the devices by dividing along the predetermined division line. Here, in order to divide the wafer into individual chips, for example, a laser beam is irradiated along the planned division line to form a modified layer inside the wafer, and an external force is applied along the planned division line with reduced strength. There is a method in which the wafer is divided into individual chips starting from the modified layer (see, for example, Patent Documents 1 and 2 below).

  Further, after the modified layer is formed inside the wafer, the wafer can be divided into individual chips starting from the modified layer, for example, by grinding the back surface of the wafer with a grinding wheel. In this wafer dividing method, the modified layer is formed in the vicinity of the front surface remaining even after the back surface grinding of the wafer, so that the wafer is divided starting from the modified layer.

JP 2011-049431 A JP 2013-0235917 A

  However, when a modified layer is formed on the inner surface side of the wafer using a laser beam as described above, warpage may occur in which the surface side of the wafer expands and the surface side becomes convex. It is difficult to accommodate the wafer in which such warpage has occurred in the cassette. In such a case, a special cassette is required to accommodate a warped wafer in the cassette.

  In addition, when the wafer with the modified layer formed is transported to the process of dividing the wafer by the transport means, a crack is generated along the modified layer due to warpage, and the wafer is broken. Cannot be held accurately, and there is a problem that the wafer cannot be transferred to a desired transfer destination.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to transport a wafer to a desired transport destination without breaking even if the wafer is warped due to the formation of a modified layer.

  The present invention relates to a wafer division that divides a wafer having a device area formed by dividing a plurality of devices by a predetermined division line and an outer peripheral surplus area surrounding the device area along the predetermined division line. A ring groove forming step of forming a ring-shaped groove centered on the center of the wafer from the front surface side of the wafer in the outer peripheral surplus area; and an inner side of the groove formed in the ring groove forming step. In the device region, a modified layer that forms a modified layer inside the wafer by condensing a laser beam having a wavelength transmissive to the wafer inside the wafer and irradiating the laser beam along the planned division line A wafer surface protecting step for attaching a protective tape for protecting the surface of the wafer to the surface of the wafer after the forming step, the modified layer forming step, and the wafer surface After the protective step, the protective tape side is held by a chuck table and the back surface of the wafer is ground with a grinding wheel to expose the groove from the back surface side and the dividing step of dividing the wafer from the modified layer, Is provided.

  In the wafer dividing method according to the present invention, after forming a ring-shaped groove from the front surface side in the outer peripheral surplus area of the wafer, a modified layer is formed inside the wafer along the planned dividing line, and the modified layer is formed by back grinding. Therefore, even if the wafer is warped due to the formation of the modified layer, the ring-shaped groove blocks the warpage, so that the warp does not reach the outer peripheral surplus region. Therefore, it is possible to prevent the wafer from being cracked due to the warpage of the wafer during conveyance before dividing the wafer, and the wafer can be easily accommodated in the cassette.

It is a perspective view which shows the structure of an example of a wafer. It is a perspective view which shows a ring groove formation process. It is sectional drawing which shows a ring groove formation process. It is sectional drawing which shows a modified layer formation process. It is sectional drawing which shows a wafer surface protection process. It is sectional drawing which shows a division | segmentation process. It is sectional drawing which shows the state which implemented the division | segmentation process and the wafer was divided | segmented.

  The wafer W shown in FIG. 1 is an example of a workpiece, and the material or the like is not particularly limited. The front surface Wa of the wafer W has a device region W1 that is partitioned by a grid-like division planned line S to form a plurality of devices D, and an outer peripheral surplus region W2 that surrounds the device region W1. On the other hand, the device D is not formed on the back surface Wb on the opposite side of the front surface Wa of the wafer W. Hereinafter, a division method for dividing the wafer W into individual chips will be described.

(1) Ring Groove Forming Step As shown in FIGS. 2 and 3, a ring-shaped groove is formed in the outer peripheral surplus area W <b> 2 of the wafer W held by the chuck table 10 using the cutting means 20. The chuck table 10 has a holding surface 11 that holds the wafer W, and can rotate around the rotation shaft 12. The cutting means 20 includes a rotatable spindle 21, a spindle housing 22 that rotatably surrounds the spindle 21, and a cutting blade 23 that is detachably attached to the tip of the spindle 21. By rotating at the rotational speed, the cutting blade 23 can be rotated at a predetermined rotational speed.

  First, the back surface Wb side of the wafer W is placed on the holding surface 11 of the chuck table 10 to expose the front surface Wa upward. Thereafter, the wafer W is sucked and held by the holding surface 11 of the chuck table 10 by operating a suction source (not shown), and the chuck table 10 is moved below the cutting means 20. The cutting means 20 lowers the cutting blade 23 in a direction approaching the outer peripheral surplus area W2 of the wafer W while rotating the cutting blade 23 in the direction of arrow B, for example, in the direction of arrow B, and the cutting edge of the cutting blade 23 is moved to the wafer. Cut into the surface Wa of W.

  Subsequently, when the chuck table 10 rotates at least once around the axis of the rotary shaft 12 in the direction of the arrow A, for example, the cutting blade 23 cuts in a ring shape around the center of the wafer W in the outer peripheral surplus region W2. A ring-shaped groove 1 is formed. The ring groove 1 is preferably formed at a position close to the device region W1 in the outer peripheral surplus region W2. More preferably, it is formed at the innermost periphery of the outer peripheral surplus region W2, that is, at the boundary with the device region W1.

  The ring groove forming step may be performed by an ablation process using a laser beam in addition to the cutting means 20 as described above. Specifically, a ring groove 1 is formed by irradiating a laser beam having a wavelength that is absorptive with respect to the wafer W from the surface Wa side of the wafer W to the outer peripheral surplus region W2 in a ring shape.

(2) Modified layer forming step After performing the ring groove forming step, the laser beam irradiation head 30 shown in FIG. 4 is used to divide the laser beam in the device region W1 inside the ring groove 1 shown in FIG. The modified layer 2 serving as a starting point for fracture is formed inside the wafer W. Specifically, the wafer W held on the chuck table 10 is moved below the laser beam irradiation head 30, and the laser beam irradiation head 30 positions the condensing point of the laser beam inside the wafer W. The condensing point is the side close to the surface Wa in the interior of the wafer W.

  Then, while moving the chuck table 10 that holds the wafer W in the direction of the arrow X1, for example, the laser beam irradiation head 30 transmits a laser beam 31 having a wavelength that is transmissive to the wafer W along the planned division line S to the surface of the wafer W. The modified layer 2 is formed by irradiating from the Wa side and condensing inside the wafer W. In this way, the modified layer 2 is formed inside the wafer W by irradiating the laser beam 31 along all the division lines S in the device region W1. When the modified layer 2 is formed on the side close to the surface Wa, the warp having a convex shape on the surface Wa side causes warpage in the device region W1, but at the boundary between the device region W1 and the excess outer region W2. Since the ring groove 1 is formed, the warpage is blocked by the ring groove 1. Accordingly, no warpage occurs in the outer peripheral surplus area W2. Further, even if a crack is generated along the modified layer 2 due to warpage, the crack is blocked by the ring groove 1, and therefore, the crack can be prevented from reaching the outer peripheral surplus region W2. .

  A plurality of wafers on which the modified layers 2 are formed in this way are stored in a cassette (not shown) and conveyed to the next wafer surface protection step. When the wafer is stored in the cassette, since the warp does not reach the outer peripheral surplus area W2, the wafer can be stored more easily than when the entire wafer is warped.

(3) Wafer Surface Protection Step After performing the modified layer forming step, the protective tape 3 is stuck to the surface Wa of the wafer W using a cylindrical sticking roller 40 as shown in FIG. Specifically, the wafers W on which the modified layer 2 is formed are unloaded from the cassette one by one. Then, the protective tape 3 is adhered to the surface Wa of the wafer W from the outer peripheral edge side of the wafer W, and the upper portion of the protective tape 3 is pressed by the adhesive roller 40 while the adhesive roller 40 is rotated in the direction of the arrow X1, for example. By moving, the protective tape 3 is attached to the entire surface Wa of the wafer W. The protective tape 3 is not particularly limited, and a protective tape having an adhesive layer on the surface side in contact with the surface Wa of the wafer W is used.

(4) Dividing Step After performing the wafer surface protecting step, as shown in FIG. 6, the wafer W held on the chuck table 13 is ground by using the grinding means 50, so that the modified layer 2 is the starting point. The wafer W is divided. The chuck table 13 has a holding surface 14 for holding the wafer W, and can rotate around the rotation shaft 15. The grinding means 50 includes at least a spindle 51 having a vertical axis, a grinding wheel 52 attached to the lower end of the spindle 51, and a grinding wheel 53 that is annularly fixed to the lower portion of the grinding wheel 52. The spindle 51 is rotated at a predetermined rotation speed by a motor (not shown), so that the grinding wheel 52 can be rotated at a predetermined rotation speed.

  When the wafer W is ground by the grinding means 50, for example, the wafer W is held by a transfer means capable of sucking and holding, and the protective tape 3 side is placed on the holding surface 14 of the chuck table 13 so that the back surface Wb of the wafer W is attached. Expose upwards. When the wafer W is transferred to the chuck table 13 in this way, even if the device region W1 shown in FIG. 2 inside the ring groove 1 is warped, the outer peripheral surplus region W2 is not warped. At least the outer peripheral surplus region W2 can be held, and the wafer W is not damaged.

  When the protective tape 3 side is placed on the holding surface 14, the protective tape 3 side is sucked and held on the holding surface 14, and the chuck table 13 is rotated, for example, in the direction of arrow A as shown in FIG. Next, while the spindle 51 is rotated and the grinding wheel 53 is rotated in the direction of arrow A, the grinding means 50 is lowered in a direction approaching the back surface Wb of the wafer W, and the rotating grinding wheel 53 is brought into contact with the back surface Wb. Then, as shown in FIG. 7, by grinding to the depth reaching the ring groove 1 while pressing the back surface Wb of the wafer W with the grinding wheel 53, the modified layer 2 becomes the starting point of breakage, and the wafer W becomes an individual device D. And the ring groove 1 is exposed from the back surface Wb, and the device region W1 and the outer peripheral surplus region W2 are separated from each other with the ring groove 1 as a boundary. After the wafer W is divided into the chips C in this way, all the chips C are transferred to the step of picking up the chips C while being stuck to the protective tape 3.

  In the wafer surface protection step, an annular ring frame having an opening at the center is attached to the tape, and the wafer W is attached to the tape exposed from the center of the ring frame. You may make it stick the protective tape 3 to. In this case, even if all the chips C are not divided from the wafer W by performing the above-described dividing step, the wafer W is surely divided into individual chips C from the modified layer 2 by expanding the tape. Can be divided. In addition, when dividing in this way, since the tape is expanded, it is necessary to remove the outer peripheral surplus area W2 before expanding.

  As described above, in the wafer dividing method of the present invention, the ring-shaped ring groove 1 is formed in the outer peripheral surplus region W2 of the wafer W by performing the ring groove forming process, and then the modified layer forming process is performed. Since the modified layer 2 is formed in the device region W1 inside the ring groove 1, even if the wafer W is warped due to the formation of the modified layer 2, since the ring groove 1 is formed, the warpage is The surplus area W2 is not reached. Moreover, even if a crack occurs along the modified layer 2, the crack does not reach the outer peripheral surplus region W2. Therefore, the wafer W can be easily transported to the chuck table 13 when the dividing step is performed.

1: ring groove 2: modified layer 3: protective tape 10: chuck table 11: holding surface 12: rotating shaft 13: chuck table 14: holding surface 15: rotating shaft 20: cutting means 21: spindle 22: spindle housing 23: Cutting blade 30: Laser beam irradiation head 31: Laser beam 40: Adhesion roller 50: Grinding means 51: Spindle 52: Grinding wheel 53: Grinding wheel W: Wafer Wa: Front surface Wb: Back surface S: Line to be divided D: Device C: Chip W1: Device area W2: Peripheral surplus area

Claims (1)

A wafer dividing method for dividing a wafer having a device area formed by dividing a plurality of devices by a planned dividing line and an outer peripheral surplus area surrounding the device area along the scheduled dividing line. ,
A ring groove forming step for forming a ring-shaped groove centered on the center of the wafer from the front surface side of the wafer in the outer peripheral surplus area;
In the device region inside the groove formed in the ring groove forming step, a laser beam having a wavelength that is transmissive to the wafer is condensed inside the wafer and irradiated along the division line. A modified layer forming step for forming a modified layer inside the wafer;
After the modified layer forming step, a wafer surface protecting step for attaching a protective tape for protecting the wafer surface to the wafer surface;
After the wafer surface protection step, the protective tape side is held by a chuck table and the back surface of the wafer is ground with a grinding wheel so that the groove is exposed from the back surface side, and the wafer is divided starting from the modified layer Process,
A wafer dividing method comprising:

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