JP2012009550A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method which can reduce strength degradation of a wafer when the wafer is circularly cut.SOLUTION: The wafer processing method of processing an outer periphery part of a wafer 11 circularly by rotating the wafer 11 while making a cutting blade cut into the outer peripheral part of the wafer 11 comprises a cutting step of rotating the wafer 11 while making the cutting blade cut into the wafer 11 to form a circular outer peripheral wall 15 at the outer periphery of the wafer 11, and a polishing step of polishing the circular outer peripheral wall 15 with a polishing pad 28 after performing the cutting step to remove a cutting distortion generated on the circular outer peripheral wall 15 in the cutting step.

Description

  The present invention relates to a wafer processing method for cutting a peripheral portion of a wafer into a circular shape by rotating the wafer while cutting a cutting blade into the peripheral portion of the wafer.

  As a method for reducing the diameter of a wafer such as a semiconductor wafer, a glass wafer, or a sapphire wafer, Japanese Patent Application Laid-Open No. 11-54461 proposes a method using a dicing apparatus equipped with a cutting blade.

  Specifically, the cutting blade is cut from the wafer surface to a depth reaching the adhesive tape at a position half the desired diameter away from the center of the wafer attached to the adhesive tape and held on the chuck table. The wafer having a small diameter is formed by rotating the wafer more than 360 degrees.

  Japanese Patent Application Laid-Open No. 2000-173961 discloses in advance that in order to prevent the wafer from being chamfered into a sharp edge (eave shape) when the wafer is thinned by grinding the back surface of the wafer, the wafer is prone to breakage. A method of forming a cutting groove in the outer peripheral portion and forming a circular outer peripheral wall is disclosed.

  In JP-A-8-107092, a cutting blade positioned on the outer periphery of a bonded wafer (SOI (Silicon on Insulator) wafer) is cut into one wafer, and the bonded wafer is rotated to rotate the outer periphery. A method for removing the unbonded region of the substrate has been proposed.

Japanese Patent Laid-Open No. 11-54461 JP 2000-173961 A JP-A-8-107092

  However, when performing circular machining as described in these patent documents with a cutting blade, the machining load becomes very large compared to normal linear machining. Therefore, when performing such circular processing, a cutting blade containing relatively coarse abrasive grains is used in order to improve machinability as compared with the case of performing linear processing.

  However, when the wafer is circularly processed with a cutting blade containing relatively coarse abrasive grains, there is a problem in that cutting distortion is formed on the formed circular outer peripheral wall and the strength of the wafer is reduced.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a wafer processing method capable of reducing a reduction in the strength of the wafer even when the outer peripheral portion of the wafer is subjected to circular processing. It is.

  According to the present invention, there is provided a wafer processing method for processing the outer peripheral portion of the wafer into a circular shape by rotating the wafer while cutting the cutting blade into the outer peripheral portion of the wafer, the cutting blade being cut into the wafer, A cutting step in which a circular outer peripheral wall is formed on the outer peripheral portion of the wafer by rotating the wafer, and after the cutting step, the circular outer peripheral wall is polished with a polishing pad and formed in the circular outer peripheral wall by the cutting step. And a polishing step for removing the cutting distortion.

  According to the present invention, a circular outer peripheral wall is formed on a wafer by circle cutting with a cutting blade, and then the circular outer peripheral wall is polished with a polishing pad. Therefore, cutting distortion formed on the circular outer peripheral wall is removed by cutting with a cutting blade. And a reduction in the strength of the wafer can be reduced.

FIG. 1A is a side view showing a cutting step of outer periphery trimming, and FIG. 1B is a side view of a state where a circular outer peripheral wall is formed by the cutting step. It is a side view which shows a grinding | polishing step. It is a disassembled perspective view of the grinding | polishing unit with which the braid | blade type | mold polishing pad was mounted | worn. It is a disassembled perspective view of the grinding | polishing unit with which the cup wheel type polishing pad was mounted | worn. It is the surface side perspective view of the wafer supported by the cyclic | annular flame | frame via the adhesive tape. FIG. 6A is a cross-sectional view showing a state in which the wafer is sucked and held by the chuck table via an adhesive tape, and FIG. 6B is a cross-sectional view showing a full-cut cutting step. FIG. 7A is a cross-sectional view of the wafer after completion of the full cut, and FIG. 7B is a cross-sectional view illustrating the polishing step. 8A is a cross-sectional view showing the polishing step when the thickness of the polishing pad is thicker than the cutting blade, and FIG. 8B is a cross-sectional view showing the polishing step when the thickness of the polishing pad is thinner than the cutting blade.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1 (A), a side view of a state in which trimming is performed on the outer peripheral portion of the wafer 11 by circle cutting with a cutting blade 20 is shown.

  On the surface 11a of the wafer 11, devices are formed in each region partitioned by a plurality of streets formed in a lattice shape as is well known. A chamfered portion 13 is formed on the outer peripheral portion of the wafer 11.

  In the cutting step for outer periphery trimming, the back surface 11b side of the wafer 11 is sucked and held by the chuck table 10 of the cutting device. Then, the cutting blade 20 of the cutting unit 12 is cut into the outer peripheral portion of the wafer 11 and the chuck table 10 is rotated at least 360 degrees, whereby the cutting blade 20 performs a circle cut.

  The cutting unit 12 holds the cutting blade 20 between a fixing flange 18 and a detachable flange 34 attached to the tip of the spindle 16 accommodated in the spindle housing 14, and fastens a fixing nut 36 to the fixing flange 18. It is configured.

  When the circle cutting is performed, a large processing load is applied to the cutting blade 20, so that a cutting blade containing relatively coarse abrasive grains is preferable with the cutting blade being 20 and it is preferable to use a cutting blade having a thickness of about 1 mm. .

  When the wafer 11 is circularly processed with the cutting blade 20 containing relatively coarse abrasive grains as described above, a cutting strain is formed on the circular outer peripheral wall 15 formed by the circular processing. Since this cutting strain causes the strength of the wafer 11 to decrease, the processing method of the present invention removes the cutting strain by polishing the circular outer peripheral wall 15 as shown in FIG.

  In the polishing unit 12 </ b> A shown in FIG. 2, a state is shown in which the circular outer peripheral wall 15 is polished using a blade-type polishing pad 28. As shown in the exploded perspective view of FIG. 3, the polishing unit 12 </ b> A has a fixed flange 18 attached to the tip end of the spindle 16 rotatably accommodated in the spindle housing 14.

  The fixing flange 18 includes a boss portion 22, a polishing pad fixing portion 24 formed integrally with the boss portion 22, and a female screw 25 formed on the boss portion 22. The fixing flange 18 is fixed to the tip end portion of the spindle 16 by screwing and tightening.

  The blade-type polishing pad 28 is configured by forming a polishing portion 32 on the outer periphery of a circular base 30 having a mounting hole 31. The mounting hole 31 of the polishing pad 28 is inserted into the boss portion 22 of the fixing flange 18, the detachable flange 34 is further inserted into the boss portion 22, and the fixing nut 36 is fastened to the female screw 25 of the boss portion 22. The polishing unit 12A is assembled as shown in FIG.

  As an alternative, the polishing unit 12B is configured by attaching a cup wheel type polishing pad 38 as shown in FIG. 4 to the boss portion 22 of the fixing flange 18 and fastening the fixing nut 36 to the female screw 25 of the boss portion 22. You may make it do.

  The polishing part 32 of the polishing pad 28 is formed from, for example, a fixed abrasive pad. Silica, alumina or the like can be used as the abrasive. While rotating the polishing pad 28, it is pressed against the circular outer peripheral wall 15 of the wafer 11, while supplying an alkaline solution as a polishing liquid, the chuck table 10 is slowly rotated to polish the circular outer peripheral wall 15 of the wafer 11 and cut distortion. Remove.

  When a polishing cloth is attached to the polishing portion 32 of the polishing pad 28, the circular outer peripheral wall 15 of the wafer 11 is polished with the polishing pad 28 while removing loose abrasive slurry, and grinding distortion is removed. Alternatively, a DP pad (dry polish pad) as disclosed in JP 2002-283243 A may be used as the polishing pad 28. In this case, dry polishing is performed without supplying any polishing liquid.

  After performing the outer periphery trimming and the polishing of the circular outer peripheral wall 15 in this way, a protective tape is attached to the front surface 11a of the wafer 11, and the back surface 11b of the wafer 11 is polished by a grinding device to thin the wafer 11.

  In this embodiment, since the circular outer peripheral wall 15 is formed by outer peripheral trimming and the chamfered portion 13 is removed, even if the wafer 11 is thinned by grinding the back surface of the wafer, the outer peripheral wall 15 of the wafer 11 has a sharp edge. Is not formed.

  Next, an embodiment in which the outer peripheral portion of the semiconductor wafer 11 is fully cut will be described with reference to FIGS. In this way, when the semiconductor wafer 11 is fully cut, the semiconductor wafer 11 is attached to the adhesive tape T whose outer peripheral portion is attached to the annular frame F as shown in FIG. As a result, the wafer 11 is supported by the annular frame F via the adhesive tape T.

  On the surface 11a of the semiconductor wafer 11, the first street S1 and the second street S2 are formed to be orthogonal to each other and each region partitioned by the first street S1 and the second street S2. Device D is formed.

  In the processing method of this embodiment, first, as shown in FIG. 6A, the wafer 11 is sucked and held by the chuck table 10 of the cutting device via the adhesive tape T, and the annular frame F is clamped by a clamp (not shown). Fix it.

  Next, as shown in FIG. 6B, the cutting blade 20 is rotated at a high speed until the tip of the cutting blade 20 reaches the adhesive tape T, and the wafer 11 is rotated while the chuck table 10 is slowly rotated in this state. The outer periphery of the material is cut into a circle (circle cut).

  As with the cutting blade 20 shown in FIG. 1A, the cutting blade 20 is a cutting blade having a relatively coarse abrasive grain and having a width of about 1 mm. The state where the circle cut is completed is shown in FIG. A circular cutting groove 17 is formed by circle cutting, and a cutting strain is formed on the circular outer peripheral wall 15 ′ of the wafer 11 inside the circular cutting groove 17.

  In order to remove the cutting distortion, as shown in FIG. 7B, the blade type polishing pad 28 of the polishing unit 12A is brought into contact with the circular cutting groove 17 while rotating at high speed, and the chuck table 10 is rotated so as to be circular. The outer peripheral wall 15 ′ facing the cutting groove 17 is polished to remove cutting distortion.

  When the polishing pad 28 is thicker than the cutting blade 20, as shown in FIG. 8A, the polishing pad 28 polishes and removes the walls on both sides of the circular cutting groove 17. 11 circular outer peripheral wall 15 'is also removed by polishing, and cutting distortion is also removed accordingly.

  In the case of the embodiment shown in FIG. 8A where the polishing pad 28 is thicker than the cutting blade 20, the walls on both sides of the circular cutting groove 17 are made to be the surface of the wafer 11 by rotating the chuck table 10 a plurality of times. It is preferable to remove by gradually polishing from the 11a side.

  On the other hand, when the thickness of the polishing pad 28 ′ is thinner than the cutting blade 20, the polishing pad 28 ′ contacts the circular outer peripheral wall 15 ′ of the wafer 11 inside the circular cutting groove 17 as shown in FIG. Thus, the polishing pad 28 'is aligned and the circular outer peripheral wall 15' is polished to remove the cutting distortion.

  In the case of the present embodiment, the polishing pad 28 'can be brought into contact with the entire length in the height direction of the circular outer peripheral wall 15' for polishing, so that the polishing pad 28 'is in pressure contact with the outer peripheral wall 15'. Polishing is performed by rotating the chuck table 10 at least once.

DESCRIPTION OF SYMBOLS 10 Chuck table 11 Semiconductor wafer 12 Cutting unit 12A Polishing unit 13 Chamfer 15,15 'Circular outer peripheral wall 20 Cutting blade 28 Polishing pad

Claims (1)

A wafer processing method for processing a wafer outer peripheral portion into a circle by rotating the wafer while cutting a cutting blade into the outer peripheral portion of the wafer,
A cutting step of forming a circular outer peripheral wall in the outer peripheral portion of the wafer by rotating the wafer while cutting the cutting blade into the wafer;
After performing the cutting step, the polishing step of polishing the circular outer peripheral wall with a polishing pad to remove the cutting strain formed on the circular outer peripheral wall in the cutting step;
A wafer processing method characterized by comprising:

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