JP5545624B2 - Wafer processing method - Google Patents

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, in order to remove the chamfered portion from the outer periphery of the wafer, when the wafer is cut with the cutting blade of the cutting blade positioned on the surface of the wafer as disclosed in Patent Document 1, a device formed on the surface of the wafer is cut. There is a problem of being contaminated with scraps.

  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. There is a problem that chipping is likely to occur.

  Furthermore, after the thin wafer is supported by the annular frame via the dicing tape, if the cutting blade is positioned on the line to be divided and then diced, chipping occurs on the outer periphery of the wafer and the quality of the device located on the outer periphery There is a problem that decreases.

  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 that does not contaminate the surface of the wafer with cutting waste and does not cause chipping on the outer periphery of the wafer. is there.

According to the present invention, there is provided a wafer processing method in which a plurality of devices are formed in an area partitioned by lines to be divided formed in a lattice shape, and an outer peripheral surplus area surrounding the device area. There is a protective tape attaching process for attaching a protective tape having an adhesive layer on the surface of which the adhesive strength is reduced by irradiating ultraviolet rays to the surface of the wafer, and the protective tape side is sucked and held by the first chuck table. Cutting the wafer into a circular shape by positioning a cutting blade on the back surface of the wafer corresponding to the boundary between the device region and the outer peripheral surplus region of the wafer held by the first chuck table. A wafer separation step of separating the device region and the outer peripheral surplus region, and the wafer separation step with a second chuck table A second wafer holding step for sucking and holding the protective tape side of the implemented wafer, a back surface corresponding to the device region of the wafer held by the second chuck table, and a back surface corresponding to the outer peripheral surplus region. The back surface of the wafer is pasted on a dicing tape that has a pressure-sensitive adhesive layer on the surface that is ground by grinding and forming a wafer to a predetermined thickness after the back surface grinding step. A wafer supporting step of attaching the outer peripheral portion of the dicing tape to an annular frame and supporting the wafer with the annular frame, and reducing the adhesive strength of the protective tape by irradiating ultraviolet rays from the back surface of the protective tape. After that, the protective tape is peeled off from the surface of the wafer, and the wafer having the device area and the outer peripheral surplus area is transferred to the dicing tape. A sorting step of changing, after該移and re step implementation, the third and the wafer holding step, the wafer held by the chuck table of the third the wafer in the third chuck table to suck and hold through the dicing tape A wafer dividing step of dividing the device area of the wafer into individual devices by cutting the device area and the outer peripheral excess area along the planned dividing line in a state where the outer peripheral area surrounds the device area; A method for processing a wafer is provided.

  According to the present invention, after attaching the protective tape to the front surface of the wafer, the 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 into a circle to obtain the device region and the outer peripheral surplus region. Therefore, the wafer surface is not contaminated with cutting waste.

  In addition, since the back surface of the wafer is ground with the outer peripheral area surrounding the device area while being 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.

  Furthermore, when the wafer is divided into individual devices, the line to be divided in the device area is cut with a cutting blade together with the outer peripheral surplus area while the peripheral outer area surrounds the device area. Is suppressed and chipping does not occur in the device region.

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 wafer separation process which cuts into a circle the boundary part of a device area | region and an outer periphery excess area | region with a cutting blade. It is sectional drawing which shows a wafer isolation | separation 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 wafer support process. It is explanatory drawing which shows an ultraviolet irradiation process. It is a perspective view 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, a wafer separation step is performed in which the protective tape 23 side is sucked and held by the chuck table 10 of the cutting apparatus, and the boundary between the device region 17 and the outer peripheral surplus region 19 is cut to form a circular separation groove. carry out.

  In this wafer separation 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 portion 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 circular separation groove 20. Separate. In FIG. 4, 22 indicates a chamfered portion.

  In the wafer separation process 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 circle, the cutting chips of the wafer are 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 by cutting waste.

  After performing the wafer separation process, a back surface grinding process for grinding the back surface 11b of the wafer 11 using a grinding apparatus 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 circular separation 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 where the grinding wheel 34 hits is easily impacted and chipped. However, since the outer peripheral surplus region 19 exists in 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.

  After the back grinding process, a wafer support process for supporting the wafer 11 with the annular frame F through the dicing tape T is performed. In this wafer support step, as shown in FIG. 7, the back surface 11b of the wafer 11 with the protective tape 23 attached to the front surface 11a is attached to the dicing tape T whose outer peripheral portion is attached 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.

  After the wafer 11 is supported by the annular frame F via the dicing tape T, the adhesive force of the protective tape 23 is reduced by irradiating ultraviolet rays from the back side of the protective tape 23 as shown in FIG. As shown, the protective tape 23 is peeled from the wafer 11.

  The wafer holding process shown in FIG. 7, the ultraviolet irradiation process shown in FIG. 8, and the protective tape peeling process shown in FIG. 9 are combined to transfer the wafer 11 having the device region 17 and the outer peripheral surplus region 19 to the dicing tape T. This is called a replacement process.

  Next, the wafer 11 is sucked and held by the chuck table 10 of the cutting apparatus as shown in FIG. 3 through the dicing tape T, and the cutting blade 18A is cut into the wafer 11 while rotating at high speed in the direction of arrow A as shown in FIG. At the same time, a chuck table (not shown) is processed and fed in the direction of the arrow X1 to cut the device region 17 and the outer peripheral surplus region 19 along the planned division line 13 to form the cutting groove 40.

  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).

  In the wafer dividing step of the present embodiment, the dividing line 13 of the device region 17 is cut with the cutting blade 18A together with the outer peripheral surplus region 19 in a state where the outer peripheral surplus region 19 surrounds the device region 17, so Microvibration generated on the outer periphery of the device 17 is suppressed, and the device region 17 is not chipped.

  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 pick-up process, the dicing tape T is expanded in the radial direction by a tape expansion device 42 as shown in FIG. 11, and the device 15 is picked up after widening the gap between devices to be picked up.

  As shown in FIG. 11A, 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. 11A, the moving cylinder 46 descends with respect to the fixed cylinder 44 as shown in FIG. 11B, 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.

DESCRIPTION OF SYMBOLS 10 Chuck table 11 Semiconductor wafer 12 Cutting unit 15 Device 17 Device area 18 Cutting blade 19 Outer peripheral area 20 Circular cutting groove 22 Chamfer 23 Protective tape 24 Chuck table 26 Grinding wheel 34 Grinding wheel T Dicing tape F Annular frame 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 sticking step of sticking a protective tape having an adhesive layer on the surface, the adhesive strength of which decreases by irradiating ultraviolet rays, to the surface of the wafer;
A first wafer holding step of sucking and holding the protective tape side with a first chuck table;
By cutting a wafer into a circular shape by positioning a cutting blade on the back surface of the wafer corresponding to the boundary between the device region of the wafer held by the first chuck table and the outer peripheral surplus region, the device region and the outer periphery A wafer separation process for separating the surplus area;
A second wafer holding step for sucking and holding the protective tape side of the wafer on which the wafer separation step has been performed by a second chuck table;
Grinding a back surface corresponding to the device region of the wafer held by the second chuck table and a back surface corresponding to the outer peripheral surplus region to form a wafer to a predetermined thickness; and
After carrying out the back surface grinding step, the back surface of the wafer is attached to a dicing tape having an adhesive layer whose adhesive strength is reduced by irradiating ultraviolet rays, and the outer peripheral portion of the dicing tape is attached to an annular frame. A wafer support step for supporting the wafer with the annular frame;
After irradiating ultraviolet rays from the back surface of the protective tape to reduce the adhesive strength of the protective tape, the protective tape is peeled off from the surface of the wafer, and a wafer having the device region and the outer peripheral region is applied to the dicing tape. A transfer process to transfer,
A third wafer holding step of sucking and holding the wafer via the dicing tape by a third chuck table after the transfer step is performed;
The device region of the wafer is cut by cutting the device region and the outer peripheral surplus region along the division line in a state where the outer peripheral surplus region of the wafer held by the third chuck table surrounds the device region. A wafer splitting process for splitting into individual devices;
A wafer processing method characterized by comprising:

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