JP2011124262A - Method of processing wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of processing a wafer free from sagging and chipping on its outer periphery. <P>SOLUTION: The method of processing the wafer having on its surface a device region in which a plurality of devices are formed in a lattice and which is formed in a region sectioned by a scheduled split line and an outer peripheral surplus region surrounding the device region includes the protective tape sticking step of sticking a protective tape onto the surface of the wafer, the auxiliary ring forming step of suction-holding the protective tape side by a chuck table, positioning a cutting blade on a boundary part between the device region and the outer peripheral surplus region from the rear surface of the wafer and cutting the wafer to form a ring-shaped cutting groove and to leave the outer peripheral surplus region as an auxiliary ring, the rear surface grinding step of grinding the rear surface of the wafer corresponding to the device region and the rear surface corresponding to the outer peripheral surplus region to form the wafer to have a predetermined thickness, and the polishing step of polishing the entire of the ground rear surface of the wafer by a polishing pad. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Semiconductor wafers that have device areas formed in areas partitioned by division lines formed in a grid shape, such as ICs and LSIs, and a surplus peripheral area surrounding the device area are ground on the back. After being thinned to a predetermined thickness, it is divided into individual devices by cutting along a division line by a dicing machine (cutting machine), and the divided devices are used in various electric devices such as mobile phones and personal computers. Widely used in equipment.

  Incidentally, a chamfered portion is formed on the outer periphery of the wafer in order to prevent the wafer from cracking and dust generation during the first half of the semiconductor wafer. Therefore, if the wafer is thinned by grinding the back surface of the wafer, the chamfered portion formed on the outer periphery of the wafer becomes a sharp knife edge shape, and the wafer is easily damaged and the operator may be injured by the knife edge. There is a problem. Therefore, Japanese Patent No. 3515917 proposes a technique for removing a chamfered portion formed on the outer periphery of the wafer before grinding the back surface of the wafer.

Japanese Patent No. 3515917

  However, if the chamfered portion is removed from the outer periphery of the wafer and the back surface of the wafer is ground and then polished with a polishing pad, the vertical cross-section formed on the outer periphery of the wafer will sag and the back surface will be slightly curved. is there.

  In addition, if the chamfered portion is removed by cutting the outer periphery of the wafer into a circle, the outer periphery of the wafer is formed into a vertical cross section. Therefore, when the back surface of the wafer is ground in the grinding process, the outer periphery of the wafer is subjected to the impact of the grinding wheel. There is a problem that chipping is likely to occur.

  The present invention has been made in view of these points, and an object of the present invention is to provide a wafer processing method in which no sagging occurs on the outer periphery of the wafer and no chipping occurs.

  According to the present invention, there is provided a wafer processing method in which a plurality of devices are formed in a region partitioned by a predetermined division line formed in a lattice shape, and an outer peripheral surplus region surrounding the device region is provided on the surface. A protective tape adhering step for adhering the protective tape to the surface of the wafer, and suction chucking the protective tape side with a chuck table to cut from the back surface of the wafer to the boundary between the device area and the outer peripheral surplus area. An auxiliary ring forming step of positioning the blade to cut the wafer to form a ring-shaped cutting groove and leaving the outer peripheral surplus area as an auxiliary ring, and corresponding to the back surface corresponding to the device area of the wafer and the outer peripheral surplus area. The back surface is ground to form a wafer with a predetermined thickness, and the entire back surface of the ground wafer is polished with a polishing pad. The wafer processing method characterized by comprising the polishing step, is provided.

  According to the present invention, the wafer is left as an auxiliary ring without removing the outer peripheral area of the wafer, and the back surface of the wafer is ground and polished with the polishing pad. Therefore, the vertical cross section formed on the outer periphery of the wafer is dipped. This can solve the problem that the back surface is slightly curved.

  In addition, since the back surface of the wafer is ground with the outer peripheral area surrounding the device area and attached to the protective tape, the impact of the grinding wheel is mitigated at the outer peripheral edge portion of the wafer device area, and the outer periphery of the wafer is Does not cause chipping.

It is a perspective view which shows a protective tape sticking process. It is a perspective view which shows the wafer holding process which hold | maintains a wafer with a chuck table. It is a perspective view which shows the auxiliary | assistant ring formation process which cuts the boundary part of a device area | region and an outer periphery excess area | region circularly with a cutting blade. It is sectional drawing which shows an auxiliary | assistant ring formation process. It is a perspective view which shows a back surface grinding process. It is sectional drawing of the wafer after a back surface grinding process. It is explanatory drawing of a grinding | polishing process. It is explanatory drawing of a wafer support process. It is explanatory drawing which shows an ultraviolet irradiation process. It is explanatory drawing which shows a protective tape peeling process. It is explanatory drawing of a wafer division | segmentation process. It is explanatory drawing of a pick-up process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The semiconductor wafer 11 shown in FIG. 1 is made of, for example, a silicon wafer having a thickness of 700 μm. A plurality of division lines (streets) 13 are formed in a lattice shape on the surface 11a, and the plurality of division schedules are formed. Devices 15 such as ICs and LSIs are formed in a plurality of regions partitioned by the lines 13, respectively.

  The wafer 11 configured as described above includes a device region 17 in which the device 15 is formed, and an outer peripheral surplus region 19 that surrounds the device region 17. A notch 21 is formed on the outer periphery of the wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

  In the wafer processing method of the present invention, in order to protect the device 15 formed on the surface 11a of the wafer 11, a protective tape 23 is attached to the surface 11a of the wafer 11 as shown in FIG. This protective tape 23 is a protective tape having an adhesive layer whose adhesive strength decreases when irradiated with ultraviolet rays, that is, an ultraviolet curable protective tape.

  Next, as shown in FIG. 2, the auxiliary ring that holds the protective tape 23 side by suction with the chuck table 10 of the cutting device and cuts the boundary between the device region 17 and the outer peripheral surplus region 19 to form a ring-shaped cutting groove. A forming step is performed.

  In this auxiliary ring forming step, the back surface 11b of the wafer 11 is exposed because the protective tape 23 side is sucked and held by the chuck table 10 as shown in FIG. A cutting blade 18 is attached to the tip of the spindle 16 rotatably accommodated in the spindle housing 14 of the cutting unit 12, and the cutting blade 18 is rotated at high speed in the direction of arrow A by a motor (not shown).

  Then, the cutting blade 18 rotating at a high speed is positioned on the back surface 11b of the wafer 11 corresponding to the boundary between the device region 17 and the outer peripheral surplus region 19 of the wafer 11, and the chuck table 10 is rotated at a low speed in the arrow B direction. As shown in FIG. 4, the boundary between the device region 17 and the outer peripheral surplus region 19 is cut to a depth reaching the protective tape 23 to form a ring-shaped cutting groove 20, and the outer peripheral surplus region 19 remains as an auxiliary ring ( Auxiliary ring forming step). In FIG. 4, 22 indicates a chamfered portion.

  In an auxiliary ring forming step in which the cutting blade 18 cuts the boundary between the device region 17 and the outer peripheral surplus region 19 of the wafer 11 into a circular shape, the wafer cutting debris is scattered, but the surface 11 a of the wafer 11 is protected by the protective tape 23. Therefore, the surface of the wafer 11 is not contaminated with cutting waste.

  After performing the auxiliary ring forming step, a back surface grinding step of grinding the back surface 11b of the wafer 11 using a grinding device is performed. That is, as shown in FIG. 5, the protective tape 23 side is sucked and held by the chuck table 24 of the grinding device to expose the back surface 11b of the wafer 11 in which the ring-shaped cutting grooves 20 are formed.

  In FIG. 5, a wheel mount 30 is fixed to the tip of a spindle 28 of the grinding apparatus, and a grinding wheel 26 is attached to the wheel mount 30 with a screw 31. The grinding wheel 26 is configured by fixing a plurality of grinding wheels 34 obtained by hardening diamond abrasive grains having a grain size of 0.3 to 1.0 μm, for example, with vitrified bonds, to a free end portion of an annular base 32.

  In this back surface grinding process, while rotating the chuck table 24 in the direction of arrow a at 300 rpm, for example, the grinding wheel 26 is rotated in the same direction as the chuck table 24, that is, in the direction of arrow b at 6000 rpm, and a grinding unit feed mechanism (not shown) Is operated to bring the grinding wheel 34 into contact with the back surface 11 b of the wafer 11.

  Then, the grinding wheel 26 is ground by a predetermined amount at a predetermined grinding feed rate (for example, 3 to 5 μm / second), and the back surface 11 b corresponding to the device region 17 and the outer peripheral surplus region 19 of the wafer 11 is ground. While measuring the thickness of the wafer 11 with a contact-type thickness measurement gauge (not shown), the wafer 11 is finished to a desired thickness, for example, 50 μm.

  FIG. 6 shows a cross-sectional view of the wafer 11 in a state where the back surface grinding has been completed. In the back surface grinding process of this embodiment, since grinding is performed with the outer peripheral surplus area 19 adhered to the protective tape 23, the edge portion of the outer peripheral surplus area 19 hit by the grinding stone 34 is easily impacted and chipped. However, since the outer peripheral surplus region 19 exists at the edge portion of the device region 17, the impact of the grinding wheel 34 is alleviated and the outer periphery of the device region 17 is not chipped.

  When the wafer 11 is ground thinly, the chamfered portion 22 has a knife edge shape as indicated by reference numeral 22a and is likely to be chipped. However, the outer peripheral surplus region 19 is discarded later, so that there is no problem.

  When the back grinding process is completed, a polishing process is performed to remove grinding distortion. In this polishing step, as shown in FIG. 7A, the side of the protective tape 23 attached to the wafer 11 subjected to back grinding is sucked and held by the chuck table 24 (shared with the grinding device) of the polishing device. A polishing wheel 29 including a base 33 and a polishing pad 35 attached to the base 33 is attached to the tip of the spindle 27 of the polishing apparatus.

  As shown in FIG. 7B, the polishing pad 35 is brought into contact with the back surface of the wafer 11 sucked and held by the chuck table 24, the chuck table 24 is rotated in the direction of arrow a, and the polishing wheel 29 is moved in the direction of arrow b. The ground surface of the wafer 11 is polished while rotating. Thereby, the grinding distortion remaining on the grinding surface is removed.

  In the processing method of this embodiment, the outer peripheral surplus region 19 of the wafer 11 is left as an auxiliary ring without being removed, and the back surface 11b of the wafer 11 is ground and polished with the polishing pad 35, which is a problem in the prior art. Further, the problem that sagging occurs in the vertical cross section formed on the outer periphery of the wafer 11 and the back surface 11b is slightly curved can be solved.

  After the polishing process, a wafer support process for supporting the wafer 11 with the annular frame F via the dicing tape T is performed. In this wafer support step, as shown in FIG. 8, the back surface 11b of the wafer 11 in a state where the protective tape 23 is adhered to the front surface 11a is adhered to the dicing tape T whose outer peripheral portion is adhered to the annular frame F. We carry out by wearing.

  The dicing tape T is an adhesive tape having an adhesive layer whose adhesive strength is reduced when irradiated with ultraviolet rays, that is, an ultraviolet curable adhesive tape. By performing the wafer support step, the wafer 11 is supported by the annular frame F via the dicing tape T.

  Next, an ultraviolet irradiation process is performed in which the selected region of the protective tape 23 is irradiated with ultraviolet rays, and the selected region of the dicing tape T is irradiated with ultraviolet rays. That is, in this ultraviolet irradiation process, as shown in FIG. 9, the ultraviolet irradiator 36 having a size corresponding to the size of the device region 15 of the wafer 11 is opposed to the back surface of the protective tape 23. The back surface of the protective tape 23 corresponding to the device area 15 is irradiated with ultraviolet rays to reduce the adhesive strength of the area corresponding to the device area 15 of the protective tape 23.

  Furthermore, the ring-shaped ultraviolet irradiator 38 having a size corresponding to the outer peripheral surplus area 19 of the wafer 11 is opposed to the back surface of the dicing tape T, and the dicing tape T in the area corresponding to the outer peripheral surplus area 19 from the back surface of the dicing tape T is used. Is irradiated with ultraviolet rays to reduce the adhesive strength of the dicing tape T in the region corresponding to the outer peripheral surplus region 19.

  Next, when the protective tape 23 is peeled off, the protective tape 23 is peeled off from the device region 17 of the wafer 11 while the outer peripheral surplus region 19 of the wafer 11 is stuck to the protective tape 23 as shown in FIG. Only the region 17 remains adhered to the dicing tape 17.

  Next, the device region 17 of the wafer 11 is sucked and held through the dicing tape T by the chuck table 10 of the cutting apparatus as shown in FIG. 3, and the cutting blade 18A is rotated at high speed in the direction of arrow A as shown in FIG. In addition to cutting into the device region 17, a chuck table (not shown) is processed and fed in the direction of the arrow X <b> 1 to form the cutting groove 40 along the division line 13.

  If the cutting grooves 40 are formed along all the division lines 13 extending in the first direction, the chuck table 10 is rotated by 90 degrees and then along all the division lines 13 extending in the second direction. By forming the same cutting groove 40, the device region 17 of the wafer 11 is divided into individual devices 15 (wafer dividing step).

  The wafer 11 that has been subjected to the wafer dividing step is then subjected to a device pickup step, and individual devices 15 are picked up from the dicing tape T. In the device pickup process, the dicing tape T is expanded in the radial direction by a tape expansion device 42 as shown in FIG. 12, and the device 15 is picked up after widening the gap between devices to be picked up.

  As shown in FIG. 12A, the tape expansion device 42 includes a fixed cylinder 44 and a moving cylinder 46 that is moved in the vertical direction by driving means disposed outside the fixed cylinder 44. An annular frame F supporting the divided wafer 11 is mounted on a moving cylinder 46 and fixed with a clamp 48. At this time, the upper surface of the fixed cylinder 44 and the upper surface of the moving cylinder 46 are held substantially in the same plane.

  When the moving cylinder 46 is moved in the direction of arrow A in FIG. 12A, the moving cylinder 46 descends with respect to the fixed cylinder 44 as shown in FIG. 12B, and accordingly the dicing tape T is expanded in the radial direction. The

  Next, when the dicing tape T is irradiated with ultraviolet rays from below the dicing tape T, the adhesive strength of the dicing tape T is reduced. Therefore, the pickup operation of the individual devices 15 by the pickup device 50 can be performed easily and smoothly.

10 chuck table 11 semiconductor wafer 12 cutting unit 15 device 17 device area 18 cutting blade 19 outer peripheral surplus area 20 ring-shaped cutting groove 22 chamfer 23 protective tape 24 chuck table 26 grinding wheel 29 polishing wheel 34 grinding wheel 35 polishing pad T dicing tape F annular frame 36, 38 UV irradiator 42 tape expansion device 50 pickup device

Claims (1)

A method of processing a wafer having a device region formed in a region partitioned by division planned lines formed in a lattice shape and a peripheral surplus region surrounding the device region on the surface,
A protective tape attaching process for attaching the protective tape to the surface of the wafer;
The protective tape side is sucked and held by a chuck table, a cutting blade is positioned at the boundary between the device region and the outer peripheral surplus region from the back surface of the wafer, and the wafer is cut to form a ring-shaped cutting groove. An auxiliary ring forming step of leaving the surplus region as an auxiliary ring;
Grinding a back surface corresponding to the device region of the wafer and a back surface corresponding to the outer peripheral surplus region to form a wafer to a predetermined thickness; and
A polishing step of polishing the entire back surface of the ground wafer with a polishing pad;
A wafer processing method characterized by comprising:

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