Method for dividing wafer

Abstract

To provide a method for dividing a wafer that causes no flaw on the front and rear surfaces of the wafer and causes no division failure even if sufficient external force is applied to the wafer.SOLUTION: A method for dividing a wafer on which a plurality of devices are partitioned and formed on a surface by scheduled division lines is configured by including: a division start point forming step of forming a division start point by applying a laser beam with a focal point positioned on a scheduled division line; a tape sticking step of sticking a tape to each of a front surface and a back surface of the wafer to sandwich the wafer with the tape; and a division step of applying external force to the division start point through the tape to divide the wafer into individual device chips.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a method for dividing a wafer having a surface on which a plurality of devices are formed and partitioned by dividing lines. [Background technology]

[0002] A wafer having a plurality of devices such as ICs and LSIs formed on its surface along dividing lines is divided into individual device chips, which are then used in electrical equipment such as mobile phones and personal computers.

[0003] As a technique for dividing a wafer into individual device chips, a technique has been proposed in which a focal point of a laser beam having a wavelength that is transparent to the wafer is positioned inside the intended dividing line, the beam is irradiated to form a modified layer inside the intended dividing line, and then an external force is applied to the wafer to divide the wafer into individual device chips (see, for example, Patent Document 1).

[0004] In addition, a technology has been proposed in which a laser beam having a wavelength that is absorbent for the wafer is focused on the surface of the intended division line and irradiated to form grooves through ablation processing, and then an external force is applied to the wafer to divide it into individual device chips (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3408805 [Patent Document 2] Japanese Patent Application Publication No. 10-305420 Summary of the Invention [Problem to be solved by the invention]

[0006] When an external force is applied to a wafer to divide it into individual device chips using the techniques described in Patent Documents 1 and 2 above, the device chips may be chipped or may not be divided completely, resulting in problems with the quality of the device chips.

[0007] In addition, in order to apply a strong external force when dividing the wafer into individual device chips so that the division is complete, it is possible to apply the external force by placing a sheet on the upper surface of the wafer. In this case, if a roller is rolled over the sheet and pressed, a strong external force can be applied to the wafer, but the device chips move after being divided into individual chips, causing the upper sheet to twist, and there is a problem that division defects occur due to the twisted sheet.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and its main technical object is to provide a method for dividing a wafer which does not cause scratches on the front and back surfaces of the wafer and does not cause division defects even when a sufficient external force is applied to the wafer. [Means for solving the problem]

[0009] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a method for dividing a wafer having a plurality of devices formed on its surface and partitioned by planned division lines, comprising: a division starting point forming step of positioning the focal point of a laser beam on the planned division line and irradiating it to form a division starting point; a tape adhering step of closely adhering tape to the front and back surfaces of the wafer to sandwich the wafer with the tape; and a division step of applying an external force to the division starting point via the tape to divide the wafer into individual device chips.

[0010] In the splitting starting point forming step, the wavelength of the laser beam is transparent to the wafer, the focal point is positioned inside the planned splitting line and irradiated, and a modified layer is formed inside along the planned splitting line to become the splitting starting point. Also, in the splitting starting point forming step, the wavelength of the laser beam is absorbent to the wafer, the focal point is positioned on the surface corresponding to the planned splitting line and irradiated, and ablation processing is performed along the planned splitting line to form a groove to become the splitting starting point.

[0011] In the dividing step, the external force applied to the dividing starting point is (1) A wafer is placed on the pad and pressed by a roller. (2) The pressure applied when the wafer is placed on the pad and the starting point of the separation is pressed vertically from above. (3) Three-point bending stress consisting of a pair of supports positioned on either side of the splitting point and a pressing point pressing the splitting point (4) Two-point bending stress in which the wafer is cantilevered by a cantilever member and the side of the dividing starting point to be pressed is exposed from the cantilever member and pressed. It is preferable that the tape adhering step includes any one of the steps 1 and 2. Also, it is preferable that in the tape adhering step, the wafer is positioned in an opening of a frame having an opening in the center for accommodating the wafer, a tape is adhered to the frame together with the wafer, and another tape is adhered to the exposed surface of the wafer so that the wafer is sandwiched between the tape and the other tape. Furthermore, after the division step, the other tape may be peeled off to expose the wafer, and the tape adhered to the frame together with the wafer may be expanded to expand the interval between the device chips.

[0012] The tape to be attached to the front and back surfaces of the wafer is (1) Adhesive tape with an adhesive layer on the surface of the sheet (2) Thermocompression tape that exerts its adhesive power when heat is applied to the sheet (3) A composite tape in which liquid resin is applied to the sheet to give it adhesive power. In the division starting point forming step, a modified layer may be formed inside along the division lines, and a groove may be formed by performing an ablation process on the front surface or the back surface corresponding to the division lines, to form a division starting point of the wafer. Effect of the Invention

[0013] The wafer dividing method of the present invention includes a dividing starting point forming step of positioning the focal point of a laser beam on a planned dividing line and irradiating it to form a dividing starting point; a tape adhering step of closely adhering tape to the front and back surfaces of the wafer to sandwich the wafer with the tape; and a dividing step of applying an external force to the dividing starting point via the tape to divide the wafer into individual device chips. Therefore, even if a strong force is applied to divide the wafer into individual device chips, the individually divided device chips are properly held by the tape adhered to the front and back surfaces, and the tape adhered to the wafer is not twisted, so the wafer can be properly divided. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a perspective view of a wafer to be divided according to the present embodiment and a first tape to be attached to the wafer. [Diagram 2] FIG. 1A is a perspective view showing how a wafer is placed on a chuck table of a laser processing device; FIG. 1B is a perspective view showing an embodiment of a splitting start point forming step; and FIG. 1C is an enlarged cross-sectional view of a portion of a wafer on which a splitting start point (modified layer) has been formed. [Diagram 3] FIG. 1 is a perspective view showing an embodiment of a grinding process. [Figure 4] FIG. 13 is a perspective view of a wafer to be divided according to another embodiment and a first tape attached to the wafer. [Diagram 5] FIG. 2 is a perspective view showing an embodiment of forming a water-soluble resin film on the surface of a wafer. [Figure 6]FIG. 1A is an oblique view showing how a wafer is placed on a chuck table of a laser processing device; FIG. 1B is an oblique view showing another embodiment of the split start point forming process; FIG. 1C is an enlarged cross-sectional view of a portion of a wafer on which split start points (grooves) have been formed; and FIG. 1D is an oblique view of a wafer on which grooves have been formed along all of the planned split lines. [Figure 7] FIG. 11 is a perspective view showing an embodiment of a tape application step. [Figure 8] FIG. 11 is a perspective view showing another embodiment of the tape application step. [Figure 9] FIG. 1A is a perspective view showing an embodiment of Example 1 of the splitting step; FIG. 1B is a perspective view showing an embodiment of Example 2 of the splitting step; FIG. 1C is a perspective view showing an embodiment of Example 3 of the splitting step; and FIG. 1D is a perspective view showing an embodiment of Example 4 of the splitting step. [Figure 10] FIG. 11 is a perspective view showing another embodiment of a tape application step. [Figure 11] FIG. 13 is a perspective view showing an embodiment in which a wafer is supported on a frame via a first tape. [Figure 12] FIG. 13 is a conceptual diagram showing an aspect of expanding a wafer by an expanding means. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a wafer dividing method according to the present invention will be described in detail with reference to the accompanying drawings.

[0016] 1 shows a perspective view of a wafer 10 to be divided by the wafer dividing method of the present embodiment, and a first tape T1 adhered in close contact with a surface 10a of the wafer 10. The wafer 10 is, for example, a silicon substrate having a plurality of devices 12 formed on the surface 10a, partitioned by division lines 14. The first tape T1 is formed to have, for example, the same dimensions as the diameter of the wafer 10.

[0017] (Split starting point formation process) When carrying out the wafer dividing method of this embodiment, a dividing start point forming step is carried out first. When carrying out the dividing start point forming step, for example, as shown in Fig. 1, a first tape T1 is closely adhered and attached to the front surface 10a of the wafer 10 to form an integrated body. The tape to be attached to the wafer 10 is not particularly limited, but is preferably selected from the tapes shown in (1) to (3) below. (1) Adhesive tape with an adhesive layer on the surface of the sheet (2) Thermocompression tape that exerts its adhesive power when heat is applied to the sheet (3) A composite tape in which a liquid resin is applied to the adhesive surface of the sheet to give it adhesive power.

[0018] The tape shown in (1) may be, for example, a sheet having a polyolefin base on which an acrylic adhesive layer is formed, and is easy to obtain and easy to handle. The tape shown in (2) is selected from materials suitable for thermocompression bonding. The material suitable for thermocompression bonding is a material that softens and exhibits adhesiveness when heated to a temperature near the melting temperature of the selected material, and can be selected from, for example, a polyolefin-based sheet or a polyester-based sheet. When a polyolefin-based sheet is used, it can be selected from a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet. When a polyester-based sheet is used, it can be selected from a polyethylene terephthalate sheet or a polyethylene naphthalate sheet. When a thermocompression tape is used, it is laid on the attachment surface of the wafer 10, heated to a temperature near the melting temperature of the selected material, and pressed by a roller or the like (not shown). According to the thermocompression tape, there is no need to provide a special adhesive layer such as a glue on the attachment surface, and no glue remains when peeled off from the wafer 10, so it is suitable for attachment to the surface 10a on which the device 12 is formed. Furthermore, the tape shown in (3) is a composite tape that is attached to the wafer 10 by laying a liquid resin on the surface of the sheet. When a water-soluble resin is used as the liquid resin, the tape can be easily peeled off by spraying water from the outer periphery of the wafer 10. In the following explanation, the thermocompression tape shown in (2) above is used as the first tape T1 and is thermocompression-bonded to the surface 10a.

[0019] As described above, once the first tape T1 has been attached to the front surface 10a of the wafer 10, the wafer is transported to a laser processing device 20 (only a portion of which is shown) shown in Fig. 2. The laser processing device 20 includes a chuck table 21 shown in Fig. 2(a) and a laser beam application means 22 shown in Fig. 2(b). The chuck table 21 includes an X-axis feed means for feeding the chuck table 21 for processing in the X-axis direction shown in Fig. 2(b), a Y-axis feed means for feeding the chuck table 21 for processing in the Y-axis direction perpendicular to the X-axis direction, and a rotary drive means for rotating the chuck table 21 (all of which are omitted from the drawings).

[0020] As shown in Fig. 2(a), the wafer 10 transported to the laser processing device 20 is placed on the holding surface 21a of the chuck table 21 with the front surface 10a side to which the first tape T1 is attached facing downward and the back surface 10b side facing upward, and is held by suction. The wafer 10 held by the chuck table 21 is aligned using an alignment means (not shown) including at least an infrared irradiation means and an imaging means for capturing infrared light, which are arranged in the laser processing device 20, to detect the position of the division lines 14 formed on the front surface 10a side, and rotate the chuck table 21 by the rotation drive means to align the division lines 14 in a predetermined direction of the wafer 10 with the X-axis direction shown in Fig. 2(b), which is the processing feed direction. Information on the position of the detected division lines 14 is stored in a control means (not shown).

[0021] Based on the position information detected by the above alignment, the condenser 23 of the laser beam application means 22 is positioned at a processing position for the predetermined dividing line 14 in a predetermined direction, as shown in Fig. 2(b). Then, the condenser of a laser beam LB1 having a wavelength that is transparent to the wafer 10 is positioned and irradiated from the back surface 10b side of the wafer 10 inside the area corresponding to the dividing line 14, and the wafer 10 is processed and fed in the X-axis direction together with the chuck table 21 to form a modified layer 100 along the predetermined dividing line 14 of the wafer 10, as shown in Fig. 2(c).

[0022] Once the modified layer 100 has been formed along a given dividing line 14, the wafer 10 is indexed and fed in the Y-axis direction by the interval of the dividing lines 14, and adjacent unprocessed dividing lines 14 in the Y-axis direction are positioned directly under the collector 23. Then, in the same manner as described above, the focusing point of the laser beam LB1 is positioned inside the dividing line 14 of the wafer 10 and irradiated, and the wafer 10 is processed and fed in the X-axis direction to form the modified layer 100. In the same manner, the wafer 10 is processed and fed in the X-axis direction and Y-axis direction to form the modified layer 100 inside along all the dividing lines 14 along the X-axis direction.

[0023] Next, the wafer 10 is rotated 90 degrees to align the unprocessed division lines 14 perpendicular to the division lines 14 on which the modified layers 100 have already been formed, in the X-axis direction. Then, for each of the remaining division lines 14, the laser beam LB1 is irradiated by positioning the focal point inside the division line 14 in the same manner as described above, to form modified layers 100 along all the division lines 14 formed on the front surface 10a of the wafer 10. In this embodiment, the processing for forming the modified layer 100 described above is performed twice (two passes) for one division line 14. This completes the division start point forming process of this embodiment.

[0024] The processing conditions for the laser processing carried out when forming the modified layer 100 described above are set, for example, as follows. Wavelength: 1064nm Repetition frequency: 100kHz Average power output: 0.4W Machining feed speed: 1000mm / sec Number of passes: 2 passes

[0025] Before carrying out the above-mentioned dividing start point forming step, if necessary, a grinding step may be carried out in which the back surface 10b of the wafer 10 is ground to reduce the thickness so as to make the wafer 10 have a desired thickness. In this case, after the above-mentioned first tape T1 is attached to the front surface 10a of the wafer 10, the wafer 10 is transported to a grinding device 40 shown in FIG. 3 before carrying out the above-mentioned dividing start point forming step.

[0026] 3, the grinding device 40 includes at least a chuck table 41 that suction-holds the wafer 10, and grinding means 42. The grinding means 42 includes a rotating spindle 43 that is rotated by a rotation drive mechanism (electric motor) not shown, a wheel mount 44 attached to the lower end of the rotating spindle 43, and a grinding wheel 45 attached to the lower surface of the wheel mount 44, and a plurality of grinding stones 46 are arranged in an annular shape on the lower surface of the grinding wheel 45.

[0027] After the wafer 10 is transported to the grinding device 40, the wafer 10 is placed on the chuck table 41 with the first tape T1 side of the wafer 10 facing downward and the back surface 10b side of the wafer 10 facing upward, and is held by suction. Next, the rotating spindle 43 of the grinding means 42 is rotated in the direction indicated by the arrow R1 in FIG. 3 at, for example, 6000 rpm, while the chuck table 41 is rotated in the direction indicated by the arrow R2 at, for example, 300 rpm. Then, while supplying grinding water onto the back surface 10b of the wafer 10 by a grinding water supplying means (not shown), the grinding wheel 45 is lowered in the direction indicated by the arrow R3, so that the grinding stone 46 comes into contact with the back surface 10b of the wafer 10. Then, the wafer 10 is ground downward at, for example, a grinding feed speed of 1.0 μm / sec. At this time, grinding can be carried out while measuring the thickness of the wafer 10 with a contact or non-contact measuring gauge (not shown), and when the back surface 10b of the wafer 10 is ground by a predetermined amount to a desired thickness, the grinding means 40 is stopped, and the grinding step of grinding the back surface 10b of the wafer 10 is completed through cleaning, drying, etc. If this grinding step is performed before the above-mentioned split start point forming step is performed, the wafer 10 after the grinding step is carried out to the laser processing device 20 described based on Fig. 2, and the split start point forming step is performed.

[0028] The splitting start point forming step of the present invention is not limited to the above embodiment. Other embodiments of the splitting start point forming step will be described below.

[0029] FIG. 4 shows a wafer 10 on which the dividing start point forming step of the present invention is processed in another embodiment, and is, for example, the same wafer as the wafer 10 described with reference to FIG.

[0030] 4, first, a first tape T1 is attached to the back surface 10b of the wafer 10. This first tape T1 can also be selected from the tapes shown in (1) to (3) above, and in this embodiment, the description will continue assuming that the tape shown in (1) above is selected and attached.

[0031] As described above, once the first tape T1 has been attached to the back surface 10b of the wafer 10 to form an integral surface, the water-soluble resin supplying means 30 is positioned on the front surface 10a side of the wafer 10, as shown in Fig. 5. Next, while rotating the wafer 10 in the direction indicated by the arrow R4, the water-soluble resin 32 is dropped and spread on the front surface 10a of the wafer 10, forming a film of the water-soluble resin 32 over the entire front surface 10a of the wafer 10. Note that forming a film of the water-soluble resin 32 on the front surface 10a of the wafer 10 is optional and can be omitted as appropriate.

[0032] As described above, after the first tape T1 is attached to the back surface 10b of the wafer 10 and the front surface 10a is coated with the water-soluble resin 32, the wafer is transferred to a laser processing device 50 (only a part of which is shown) shown in Fig. 6. The laser processing device 50 has a configuration similar to that of the laser processing device 20 described above, and includes a chuck table 51 shown in Fig. 6(a) and a laser beam application means 52 shown in Fig. 6(b). The chuck table 51 includes an X-axis feed means for feeding the chuck table 51 in the X-axis direction shown in Fig. 6(b), a Y-axis feed means for feeding the chuck table 51 in the Y-axis direction perpendicular to the X-axis direction, and a rotary drive means for rotating the chuck table 51 (all of which are omitted from the drawings).

[0033] The wafer 10 transported to the laser processing device 50 is placed on the chuck table 51 and held by suction with the back surface 10b to which the first tape T1 is attached facing downward and the front surface 10a coated with the water-soluble resin 32 facing upward. The wafer 10 held on the chuck table 51 is aligned using an alignment means (not shown) arranged in the laser processing device 50 to detect the positions of the division lines 14 formed on the front surface 10a, and the wafer 10 is rotated by the rotation drive means to align the division lines 14 in a predetermined direction with the X-axis direction shown in FIG. 6(b). Information on the detected positions of the division lines 14 is stored in a control means (not shown).

[0034] Based on the positional information detected by the above-mentioned alignment, the collector 53 of the laser beam application means 52 is positioned at the processing start position of the planned dividing line 14 in a predetermined direction, and the focal point of the laser beam LB2 having a wavelength that is absorbent for the wafer 10 is positioned and irradiated on the surface 10a of the planned dividing line 14 of the wafer 10. At the same time, the wafer 10 is processed and fed together with the chuck table 51 in the X-axis direction to perform ablation processing along the predetermined planned dividing line 14 of the wafer 10, and a groove 110 serving as the dividing start point is formed on the surface 10a side coated with the water-soluble resin 32, as shown in Figure 6(c).

[0035] After the grooves 110 are formed along the predetermined dividing lines 14, the wafer 10 is indexed and fed in the Y-axis direction by the interval of the dividing lines 14, and the unprocessed dividing lines 14 adjacent in the Y-axis direction are positioned directly under the condenser 53. Then, in the same manner as described above, the focal point of the laser beam LB2 is positioned on the surface 10a of the wafer 10 corresponding to the dividing lines 14, and the wafer 10 is fed in the X-axis direction to form the grooves 110. Similarly, the wafer 10 is fed in the X-axis direction and the Y-axis direction to form the grooves 110 along all the dividing lines 14 along the X-axis direction. Next, the wafer 10 is rotated 90° to align the unprocessed dividing lines 14 in the direction perpendicular to the dividing lines 14 on which the grooves 110 have already been formed in the X-axis direction. Then, the focal point of the laser beam LB2 is positioned and irradiated to the remaining dividing lines 14 in the same manner as described above. As a result, grooves 110 are formed along all the dividing lines 14 formed on the front surface 10a of the wafer 10. Thereafter, pure water or the like is sprayed onto the front surface 10a of the wafer 10 to remove the water-soluble resin 32, and as shown in FIG. 6(d), a wafer 10 is obtained in which the grooves 110 are formed along the dividing lines 14 on the front surface 10a, completing the dividing start point forming step of this embodiment. In this embodiment, the laser beam LB2 is irradiated four times (four passes) along the dividing lines 14 to form grooves 110 of a desired depth. As described above, when the laser beam LB2 is irradiated onto the wafer 10 to perform the ablation process, the front surface 10a of the wafer 10 is coated with the water-soluble resin 32, so that the front surface 10a of the wafer 10 is prevented from being contaminated by debris or the like generated by the ablation process using the laser beam LB2, and the film of the water-soluble resin 32 to which the debris or the like is attached is easily removed by pure water or the like.

[0036] The processing conditions for the laser processing performed when the groove 110 is formed by the above-mentioned laser processing device 50 are set, for example, as follows. Wavelength: 355nm Repetition frequency: 10kHz Average power: 3.6W Machining feed speed: 150mm / sec Number of passes: 4 passes

[0037] As described above, after the grooves 110 are formed by performing the ablation process along all the division lines 14 formed on the front surface 10a of the wafer 10 in the division start point forming process, a grinding process may be performed as necessary to grind the back surface 10b of the wafer 10 to thin it to a desired thickness. When performing the grinding process of grinding the back surface 10b of the wafer 10, an appropriate tape is selected from the tapes shown in (1) to (3) above, and the tape is adhered to the front surface 10a. Next, the first tape T1 previously adhered to the back surface 10b of the wafer 10 is peeled off, leaving the back surface 10b exposed. Thereafter, the back surface 10b of the wafer 10 is ground in the same procedure as the grinding process described based on FIG. 3 to perform a grinding process to thin it to a desired thickness (detailed description will be omitted).

[0038] In addition, when the splitting starting point formation process performs ablation processing along all of the planned splitting lines 14 formed on the front surface 10a of the wafer 10 to form grooves 110, it is not necessarily limited to forming the grooves 110 on the front surface 10a side of the wafer 10, and the above-mentioned grooves 110 may be formed at positions corresponding to the planned splitting lines 14 on the back surface 10b side of the wafer 10.

[0039] In addition, in the above-mentioned splitting starting point formation process, only one of forming a modified layer 100 inside the wafer 10 along the planned splitting line 14 and forming a groove 110 along the surface corresponding to the planned splitting line 14 is carried out, but the present invention is not limited to this, and it is also possible to form the modified layer 100 inside along the planned splitting line 14 and perform the above-mentioned ablation processing at a position corresponding to the planned splitting line 14 on the front surface 10a or the back surface 10b to form a groove 110 as a splitting starting point for the wafer.

[0040] (Tape application process) As described above, after the division starting point forming step is performed, a tape adhering step is performed in which tape is closely attached to the front surface 10a and the back surface 10b of the wafer 10 to sandwich the wafer 10 with the tape. In the division starting point forming step described above, the first tape T1 has already been attached to the front surface 10a or the back surface 10b, and in the tape adhering step described below, the tape is attached to the other surface to which the first tape T1 is not attached, thereby completing the tape adhering step.

[0041] As described above, the wafer 10 in which the modified layer 100 is formed as a division starting point inside the division line 14 has the first tape T1 attached to the front surface 10a side in advance. As shown in FIG. 7, the second tape T2 is prepared for this wafer 10 and attached in close contact to the back surface 10b to which the first tape T1 is not attached. This sandwiches the wafer 10 between the first tape T1 and the second tape T2, completing the tape attachment process. The second tape T2 can also be appropriately selected from the tapes shown in (1) to (3) above and attached. When selecting the second tape T2, the same tape as the first tape T1 may be selected, or a different tape may be selected.

[0042] In addition, as shown in FIG. 6(d), the first tape T1 is attached to the back surface 10b side of the wafer 10 in which the groove 110 is formed as the dividing starting point. As shown in FIG. 8, the second tape T2 is prepared for this wafer 10 and is attached in close contact with the front surface 10a. This allows the wafer 10 to be sandwiched between the first tape T1 and the second tape T2, completing the tape attachment process. The second tape T2 can also be appropriately selected from the tapes shown in (1) to (3) above and attached. When selecting the second tape T2, the same tape as the first tape T1 may be selected, or a different tape may be selected. As the tape to be attached to the front surface 10a of the wafer 10, the thermocompression tape shown in (2) that does not leave any adhesive or the like after peeling is preferable.

[0043] In addition, when a grinding process is performed in which the back surface 10b of the wafer 10 is ground to a desired thickness after the groove 110 is formed on the front surface 10a of the wafer 10 by the dividing start point forming process, a tape is adhered to the front surface 10a side of the wafer 10 (this is referred to as the first tape T1), and the back surface 10b is exposed. Therefore, in this case, the above-mentioned second tape T2 is adhered to the back surface 10b of the wafer 10 in such a manner that the wafer 10 is sandwiched between the first tape T1 and the second tape T2. When selecting this second tape T2, it is possible to appropriately select and adhere it from the tapes shown in (1) to (3) above, and the same tape as the first tape T1 may be selected, or a different tape may be selected.

[0044] (splitting process) As described above, after the division starting point forming step and the tape adhering step are performed, a division step is performed in which an external force is applied to the above-mentioned division starting points via the tape to divide the wafer 10 into individual device chips. The method for performing the division step is not particularly limited, and for example, the methods of Examples 1 to 4 shown below can be selected. In the following description, a case will be described in which a modified layer 100 is formed as a division starting point inside the division line 14, and the wafer 10 having a first tape T1 attached to the front surface 10a and a second tape T2 attached to the back surface 10b is divided into individual device chips.

[0045] Example 1 After the tape application process for the wafer 10 is completed as described above, a pad 60 shown in FIG. 9(a) is prepared, and the wafer 10 is placed on the pad 60 with the first tape T1 facing upward. At this time, the predetermined dividing line 14 of the wafer 10 is positioned in the X-axis direction indicated by the arrow X in the figure. The pad 60 is a circular pad formed with a diameter larger than the wafer 10 and having elasticity, and is made of, for example, hard urethane. Next, a roller 62 as shown in the figure is prepared and positioned on the wafer 10. The roller 62 is made of a hard member (for example, a metal roller). The dividing line 14 on which the modified layer 100 is formed on the wafer 10 can be visually confirmed through the first tape T1, and the roller 62 is positioned so as to follow the dividing line 14 aligned in the X-axis direction.

[0046] Next, the roller 62 is pressed from above at one end of the wafer 10 and moved in the direction indicated by the arrow R6 (Y-axis direction in the figure) while rotating in the direction indicated by the arrow R5. This allows the wafer 10 to be applied with a pressing force accompanied by rotation, and the wafer 10 is divided with the modified layer 100 formed along the intended dividing line 14 as the dividing starting point. After the roller 62 has been moved from one end of the wafer 10 to the other end, the wafer 10 is rotated by 90°, and the roller 62 is pressed from above the wafer 10 and moved from one end to the other end while applying a pressing force accompanied by rotation to the wafer 10 in the same manner as described above. This divides the wafer 10 into individual device chips along the dividing starting points, completing the dividing process.

[0047] As described above, the wafer 10 has a dividing starting point formed by the modified layer 100, and is sandwiched by tape attached to the front surface 10a and back surface 10b of the wafer 10. Therefore, even if a strong pressing force is applied from above to divide the wafer 10 into individual device chips, the individual divided device chips are properly held by the tape attached to the front surface 10a and back surface 10b, and the tape on the surface to which the pressing force is applied is not twisted, and the wafer 10 is properly divided.

[0048] Example 2 As shown in FIG. 9(b), a pad 60 similar to that of the first embodiment is prepared, and the wafer 10 is placed on the pad 60 with the first tape T1 facing upward. Next, a wedge-shaped pressing member 63 having a straight pressing portion 63a with an acute angle downward and formed longer than the diameter of the wafer 10 is positioned above the wafer 10. Next, the pressing member 63 is pressed vertically from above as shown by the arrow R7 against the dividing line 14 on which the modified layer 100 is formed as a dividing starting point through the first tape T1 attached to the front surface 10a of the wafer 10, thereby applying a pressing force, and the wafer 10 is divided along the dividing line 14. Next, the pressing member 63 is moved in the direction shown by the arrow R8, and positioned adjacent to the dividing line 14 that has already been divided and on the dividing line 14 that has not yet been divided, and pressed vertically from above to apply a pressing force, thereby dividing the wafer 10 along the dividing line 14. By repeating these steps, the wafer 10 is divided along the division starting points (modified layers 100) of all of the division lines 14 formed in a predetermined direction. Next, the wafer 10 is rotated 90°, and in the same manner as described above, the pressing member 63 is pressed from above the wafer 10 against the division lines 14 where the division starting points are formed, and moved from one end to the other end to apply a pressing force that presses vertically from above against the division lines 14 of the wafer 10. As a result, the wafer 10 is divided into individual device chips, and the division process is completed.

[0049] As described above, the wafer 10 has a division starting point formed by the modified layer 100, and is sandwiched by tape affixed to the front surface 10a and back surface 10b of the wafer 10. Therefore, even if a strong pressing force is applied from above to divide the wafer 10 into individual device chips, the individual divided device chips are properly held by the tape affixed to the front surface 10a and back surface 10b, and the tape on the surface to which the pressing force is applied is not twisted, and the wafer 10 is properly divided into individual device chips.

[0050] Example 3 Instead of the pad 60 shown in the above-mentioned Examples 1 and 2, a support base 64 is prepared on the underside of the wafer 10, the support base 64 having a pair of fulcrums 64a, 64b aligned in the X-axis direction so as to sandwich the planned division line 14 on which the modified layer 100 is formed as the starting point of division. In addition, a wedge-shaped pressing member 63 is prepared, which is also provided in the above-mentioned Example 2 and has a straight pressing portion 63a with an acute angle on the lower side and is formed longer than the diameter of the wafer 10.

[0051] After the support base 64 and the pressing member 63 are prepared, the first tape T1 of the wafer 10 is placed on the support base 64 with the first tape T1 facing upward, so that the predetermined dividing line 14 is aligned with the center of the pair of fulcrums 64a, 64b. Next, the pressing portion 63a of the pressing member 63 shown in the figure is positioned on the dividing line 14 positioned at the center of the pair of fulcrums 64a, 64b, and pressed vertically from above as shown by the arrow R7 through the first tape T1 attached to the front surface 10a of the wafer 10. The dividing line 14 pressed by the pressing member 63 is sandwiched and supported by the fulcrums 64a, 64b of the support base 64 from the lower surface side of the wafer 10, and the dividing line 14 sandwiched between the fulcrums 64a, 64b is pressed by the pressing portion 63a of the pressing member 63, and a three-point bending stress is applied to divide the wafer.

[0052] Next, the pressing member 63 and the support base 64 are moved in the direction indicated by the arrow R8 (or moved on the wafer 10 side in the opposite direction to the arrow R8) to position the dividing line 14 adjacent to the already divided dividing line 14 and not yet divided along the center of the fulcrums 64a, 64b, and the pressing part 63a of the pressing member 63 is pressed vertically from above to apply a three-point bending stress along the dividing line 14, thereby dividing the dividing line 14. By repeating these steps, the wafer 10 is divided along the dividing starting point (modified layer 100) of the dividing line 14 formed in a predetermined direction. Next, the wafer 10 is rotated 90°, and while moving the pressing member 63 and the support base 64 in the same manner as described above, the pressing member 63 is pressed against the division lines 14 where the division start points are formed from above the wafer 10 to apply three-point bending stress, and the pressing member 63 and the support base 64 are moved from one end to the other end to apply three-point bending stress to all of the division lines 14 of the wafer 10. As a result, the wafer 10 is divided into individual device chips, and the division process is completed.

[0053] Also in the above-mentioned Example 3, tape is attached to the front surface 10a and back surface 10b of the wafer 10 to form a sandwich state, so that even if a three-point bending stress is applied to divide the wafer 10 into individual device chips, the individual divided device chips are properly held by the tape attached to the front surface 10a and back surface 10b, and the tape attached to the front surface 10a and back surface 10b of the wafer 10 does not twist, and the wafer 10 is properly divided into individual device chips.

[0054] Example 4 9(d), the present embodiment 4 uses a cantilever member 65 that cantilevers the wafer 10, and a pressing member 66. The embodiment shows a mode in which the wafer 10 cantilevered by the cantilever member 65 is pressed on the split starting point side exposed from the cantilever member 65 to apply two-point bending stress to split the wafer 10.

[0055] As shown in the figure, the cantilever member 65 has a horizontally formed gap 65a that cantilevers the wafer 10, which is sandwiched between the front surface 10a and the back surface 10b and has tape attached thereto. An opening 65b is formed in the gap 65a along the X-axis direction. The size of the gap 65a can be finely adjusted by an adjustment means (not shown), and the wafer 10 can be supported by inserting the wafer 10 into the gap 65a and narrowing the gap 65a.

[0056] When dividing the wafer 10 according to this Example 4, the first tape T1 attached to the front surface 10a of the wafer 10 is inserted into the gap 65a of the cantilever member 65 so as to face upward and cantilever the wafer 10. At this time, the division line 14 in a predetermined direction of the wafer 10 is inserted while being aligned with the X-axis direction shown in the figure, and the division line 14 on which the modified layer 100, which is the division starting point at one end on the front side in the figure, is positioned at the opening 65b of the cantilever member 65, and the one end side is exposed outward from the opening 65b of the cantilever member 65.

[0057] The pressing member 66 shown in the figure is a flat member having a pressing portion 66a with an acute angle on the lower side. The length of the pressing portion 66a is formed to be longer than the diameter of the wafer 10. As described above, after one end side of the wafer 10 on the front side in the figure is exposed from the opening 65b, the pressing member 66 is lowered in the direction indicated by the arrow R9 along the front surface 65c of the cantilever member 65. As a result, a pressing force is applied by the pressing portion 66a of the pressing member 66 along the division lines 14 of the wafer 10 supported by the opening 65b, and a two-point bending stress is applied to the division lines 14, thereby dividing the wafer 10 along the division lines 14 of the wafer 10.

[0058] After dividing the wafer 10 along the dividing lines 14 as described above, the wafer 10 is pulled out from the gap 65a of the cantilever member 65 in the direction indicated by the arrow R10 (Y-axis direction) by the distance of the dividing lines 14, and the dividing lines 14 that have not yet been divided are aligned with the openings 65b, and the pressing member 66 is lowered along the front surface 65c where the openings 65b of the cantilever member 65 are formed, in the same manner as described above, to apply two-point bending stress to the dividing lines 14 of the wafer 10 supported by the gaps 65a of the cantilever member 65, thereby dividing the wafer 10 along the dividing lines 14 of the wafer 10. By repeating these steps, the wafer 10 is divided along the dividing starting points (modified layer 100) of all the dividing lines 14 formed in a predetermined direction. Next, the wafer 10 is rotated 90°, and in the same manner as described above, the wafer 10 is supported by being sandwiched between the gaps 65a of the cantilever members 65, and a two-point bending stress is applied from above the wafer 10 along the dividing lines 14 where the dividing start points are formed by the pressing member 66 to divide the wafer 10 along the dividing lines 14, while the wafer 10 is pulled out at the intervals along the dividing lines 14, and a two-point bending stress is applied along the dividing lines 14 of the wafer 10 to divide the wafer 10. As a result, the wafer 10 is divided into individual device chips, and the dividing process is completed. Although not shown, it is preferable to provide a sandwiching member near the openings 65b of the cantilever members 65 to sandwich the wafer 10 along the dividing lines 14 when dividing the wafer 10.

[0059] In the above-mentioned Example 4, too, tape is attached to the front surface 10a and back surface 10b of the wafer 10 to form a sandwich state, so that even if two-point bending stress is applied along the intended division line 14 to divide the wafer 10 into individual device chips as described above, the individually divided device chips are properly held by the tape attached to the front surface 10a and back surface 10b, and the tape to which stress is applied by the cantilever member 65 and the pressing member 66 does not twist, and the wafer 10 is properly divided into individual device chips.

[0060] In the dividing step of the above embodiment, a modified layer 100 is formed as a dividing starting point inside the dividing line 14, and the wafer 10 having the first tape T1 attached to the front surface 10a and the second tape T2 attached to the back surface 10b is divided into individual device chips. However, the present invention is not limited to this, and even if the wafer 10 is divided into individual device chips by forming grooves 110 as dividing starting points along the dividing line 14, it is possible to divide the wafer 10 in the same manner as described above. In addition, when performing the dividing step of the above embodiments 1 to 4, an external force may be applied along the dividing line 14 with the second tape T2 side of the wafer 10 facing upward to divide the wafer 10 into individual device chips.

[0061] In the above embodiment, the tapes (first tape T1, second tape T2) adhered in close contact to the front surface 10a and back surface 10b of the wafer 10 in the tape adhering step have the same dimensions as the diameter of the wafer 10, but the present invention is not limited to this. The present invention also includes, for example, other embodiments described below.

[0062] In carrying out another embodiment described below, an annular frame F having an opening Fa capable of accommodating a wafer 10 and a third tape T3 formed to a size capable of covering the opening Fa are prepared as shown in Fig. 10. The third tape T3 can be selected from the tapes shown in (1) to (3) above, for example, and in this embodiment, the description will be given assuming that the tape shown in (1) is selected.

[0063] Once the frame F and third tape T3 described above are prepared, as shown in Fig. 10, the front surface 10a of the wafer 10 is positioned in the center of the opening Fa of the frame F with the front surface 10a facing upward, and the third tape T3 is attached to the back surface 10b of the wafer 10 and the back surface of the frame F. As a result, the wafer 10 is supported by the frame F via the third tape T3.

[0064] As described above, once the wafer 10 has been supported on the frame F via the third tape T3, a splitting starting point forming process is carried out in which a laser beam LB2 having a wavelength absorbed by the wafer 10 is irradiated along all of the planned splitting lines 14 formed on the front surface 10a of the wafer 10 with a focal point located using the same procedures and laser processing conditions as those described based on Figures 5 and 6, thereby forming grooves 110 that serve as splitting starting points (details will be omitted).

[0065] After the division starting point forming step is performed as described above, as shown in FIG. 11, the fourth tape T4 is adhered to the front surface 10a of the wafer 10. The fourth tape T4 can also be selected from the tapes shown in (1) to (3) above, and in this embodiment, for example, the thermocompression tape shown in (2) is selected. The procedure for adhering the thermocompression tape to the front surface 10a of the wafer 10 is as described in the embodiment described above, and detailed description will be omitted. As a result, the wafer 10 is sandwiched between the third tape T3 and the fourth tape T4 to form a sandwich-like body, and the tape adhering step of this embodiment is completed. The fourth tape T4 shown in the figure is formed to have the same dimensions as the wafer 10, but may be formed to have dimensions that cover the opening Fa of the frame F, similar to the third tape T3.

[0066] After the dividing start point forming step and the tape attaching step are performed as described above, the dividing step is performed. The dividing step can be performed by appropriately applying the method described with reference to Fig. 9, but considering that the wafer 10 is supported by the frame F, it is preferable to perform the dividing step by the method described with reference to Figs. 9(a) to (c).

[0067] As described above, even if the wafer 10 is supported by the annular frame F via the third tape T3, it is possible to carry out the division start point forming step, tape adhering step, and division step of the present invention. In the division start point forming step described based on Figs. 10 and 11, the wafer 10 is supported by the frame F with the front surface 10a facing upward and the third tape T3 adhered to the back surface 10b side, and the wafer 10 is irradiated from the front surface 10a side along the planned division line 14 to form the groove 110 serving as the division start point, but the present invention is not limited to this. For example, when the wafer 10 is supported by the annular frame F via the third tape T3, the back surface 10b of the wafer 10 is positioned at the opening Fa of the frame F with the back surface 10b facing upward, and the third tape T3 is adhered together with the front surface 10a of the wafer 10 and the wafer 10 is supported by the frame F. 2, a laser beam LB1 having a wavelength that is transparent to the wafer 10 may be irradiated from the back surface 10b side of the wafer 10 to position a focal point within the dividing line 14 of the wafer 10, thereby forming a modified layer 100 serving as a dividing starting point along the dividing line 14. In this case, in the tape adhering step, a fourth tape T4 is closely adhered to the back surface 10b of the wafer 10, and a tape adhering step is performed in which the wafer 10 is sandwiched between the third tape T3 and the fourth tape T4, thereby carrying out the dividing step described above.

[0068] As described above, when the wafer 10 is supported by the annular frame F via the third tape T3 and the dividing step is performed by sandwiching the wafer 10 between the third tape T3 and the fourth tape T4, after the dividing step is performed, the fourth tape T4 may be peeled off to expose the wafer 10, and the third tape attached to the frame F together with the wafer 10 may be expanded to expand the spacing between the device chips 12' (see Figure 12) formed by dividing the wafer 10.

[0069] When expanding the third tape T3, an expansion means 70, the outline of which is shown in FIG. 12, is prepared. As shown in FIG. 12, the expansion means 70 includes a cylindrical expansion drum 72a, a plurality of air cylinders 72b adjacent to the expansion drum 72a and extending upward at intervals in the circumferential direction, annular holding members 72c connected to the upper ends of the air cylinders 72b, and a plurality of clamps 72d arranged at intervals in the circumferential direction on the outer periphery of the holding member 72c. The inner diameter of the expansion drum 72a is larger than the diameter of the wafer 10, and the outer diameter of the expansion drum 72a is smaller than the inner diameter of the frame F. The holding member 72c corresponds to the diameter dimension of the frame F, and the frame F is placed on the flat upper surface of the holding member 72c.

[0070] As shown in Fig. 12, the multiple air cylinders 72b raise and lower the holding member 72c between a reference position where the upper surface of the holding member 72c is at approximately the same height as the upper end of the expansion drum 72a and an expansion position where the upper surface of the holding member 72c is located below the upper end of the expansion drum 72a. Note that, for convenience of explanation, in Fig. 12, the wafer 10 held by the illustrated third tape T3 is shown to rise and fall together with the expansion drum 72a (shown by solid lines and two-dot chain lines), but in reality, it is the holding member 72c that rises and falls.

[0071] When expanding the third tape T3 supporting the wafer 10, first, the fourth tape T4 is peeled off from the surface 10a of the wafer 10 on which the above-mentioned division process has been carried out, exposing the surface 10a of the wafer 10. Next, the surface 10a of the wafer 10 divided into individual device chips 12' is turned up, and a frame F is placed on the upper surface of the holding member 72c positioned at the reference position, and the frame F is fixed by a plurality of clamps 72d. Next, by lowering the holding member 72c to the expansion position, the wafer 10 is expanded together with the third tape T3, as shown by the two-dot chain line in FIG. 12, and the intervals between the device chips 12' of the wafer 10 attached to the third tape T3 are expanded. This makes it possible to pick up the device chips 12' divided from the wafer 10 by an appropriate pick-up means (not shown), and the picked-up device chips 12' can be transported to the next process or stored in an appropriate storage case. [Explanation of symbols]

[0072] 10: Wafer 10a: surface 10b: Back side 12: Device 12': Device chip 14: Planned division line 20: Laser processing equipment 21: Chuck table 22: Laser beam irradiation means 23: Concentrator 30: Water-soluble resin supply means 32: Water-soluble resin 40: Grinding equipment 41: Chuck table 42: Grinding means 43: Rotating spindle 45: Grinding wheel 46: Grinding wheel 50: Laser processing equipment 51: Chuck table 52: Laser beam irradiation means 53: Concentrator 60: Pad 62: Laura 63: Pressing member 63: Pressing part 64:Support base 64a: Fulcrum 65: Cantilevered member 65a: Gap 65b: Opening 65c:Front 66: Pressing member 66a: Pressing part 70: Expansion means 72a: Extended drum 72b: Air cylinder 72c: Retaining member 72d: Clamp 100: Modified layer 110: Groove T1: First Tape T2: The Second Tape

Claims

1. A method for dividing a wafer having a surface on which a plurality of devices are formed and partitioned by dividing lines, comprising the steps of: a division starting point forming step of irradiating a laser beam with a focal point positioned on a planned division line to form a division starting point; a tape application process in which tape is applied to the front and back surfaces of the wafer in intimate contact with each other to sandwich the wafer between the tapes; a dividing step of dividing the wafer into individual device chips by applying an external force to the dividing starting points via a tape; A wafer dividing method comprising the steps of:

2. In the division starting point forming step, The wavelength of the laser beam is transparent to the wafer; 2. The method for dividing a wafer according to claim 1, wherein the focal point is positioned inside the dividing line and irradiated with light, and a modified layer is formed inside along the dividing line and serves as a dividing starting point.

3. In the division starting point forming step, The wavelength of the laser beam is absorbed by the wafer, 2. A method for dividing a wafer according to claim 1, wherein the focal point is positioned on the surface corresponding to the intended dividing lines and irradiated, and ablation processing is performed along the intended dividing lines to form grooves which become dividing starting points.

4. In the division step, The external force applied to the starting point of the split is (1) Pressing force with rotation of rollers while placing a wafer on the pad (2) The pressure applied when the wafer is placed on the pad and the starting point of the division is pressed vertically from above. (3) Three-point bending stress consisting of a pair of supports positioned on either side of the splitting point and a pressing point pressing the splitting point (4) Two-point bending stress in which the wafer is cantilevered by a cantilever member and the side of the dividing starting point to be pressed is exposed from the cantilever member and pressed.

2. The method for dividing a wafer according to claim 1, comprising any one of the steps of:

5. In the tape application step, 2. A method for dividing a wafer according to claim 1, comprising the steps of: positioning the wafer in an opening of a frame having an opening in the center for accommodating the wafer; attaching a tape to the frame together with the wafer; and attaching another tape to the exposed surface of the wafer so that the wafer is sandwiched between the tape and the other tape.

6. 6. The method for dividing a wafer according to claim 5, further comprising the steps of: after the dividing step, peeling off the other tape to expose the wafer; and expanding the tape attached to the frame together with the wafer to expand the spaces between the device chips.

7. The tape to be attached to the front and back surfaces of the wafer is (1) Adhesive tape having an adhesive layer on the surface of the sheet (2) Thermocompression tape that exerts its adhesive power by applying heat to the sheet (3) Composite tape in which liquid resin is applied to the sheet to give it adhesive power 2. The method for dividing a wafer according to claim 1, wherein the method is any one of the above or a combination thereof.

8. In the division starting point forming step, 4. A method for dividing a wafer according to claim 2 or 3, further comprising forming a modified layer inside along the intended dividing lines, and performing an ablation process on the front or back surface corresponding to the intended dividing lines to form grooves, thereby forming starting points for dividing the wafer.

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