Stacked wafer processing method

Abstract

To provide a method of processing a stacked wafer without reducing the quality of a first wafer even when a region corresponding to projected dicing lines is removed from a second wafer and the projected dicing lines formed on the surface of the first wafer is exposed.SOLUTION: There is provided a method of processing a stacked wafer including a first wafer and a second wafer stacked on a surface of the first wafer, the first wafer having a plurality of devices formed on the surface that are demarcated by a plurality of projected dicing lines. The method includes: a modified layer forming step of positioning a focused spot of a laser beam having a wavelength with transmissivity inside two sides defining the projected dicing lines, and applying the laser beam to the second wafer from an upper surface side of the second wafer, thereby forming at least two strips of modified layers inside the second wafer along the projected dicing lines; a tape affixing step of affixing a tape to the upper surface of the second wafer; and a projected dicing line exposing step of peeling off the tape from the upper surface of the second wafer to remove, from the second wafer, end materials which correspond to the projected dicing lines and in which the modified layers are formed along the projected dicing lines, thereby exposing the projected dicing lines formed on the surface of the first wafer.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for processing a laminated wafer in which a second wafer is laminated on the front surface of a first wafer having a plurality of devices formed on the front surface thereof by partitioning along planned division lines. [Background technology]

[0002] Wafers, on whose surface multiple devices such as ICs and LSIs are formed, are divided along planned dividing lines. These are then separated into individual device chips using a dicing machine or laser processing machine. These are then used in electrical equipment such as mobile phones and personal computers.

[0003] In addition, a stacked wafer such as an SOI wafer in which a second wafer is stacked on the surface of a first wafer having a plurality of devices partitioned by planned dividing lines is also divided along the planned dividing lines to form two layers of device chips (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-230971 A Summary of the Invention [Problem to be solved by the invention]

[0005] When processing the above-mentioned laminated wafer, a processing step may be performed in which the area of ​​the second wafer corresponding to the dividing line is removed to expose the dividing line formed on the surface of the first wafer. In this case, if a cutting blade is used to remove the area corresponding to the dividing line from the second wafer, there is a problem that the cutting blade contacts the first wafer, resulting in a deterioration in quality. To address this, it is necessary to adjust the cutting depth of the cutting blade so as not to contact the first wafer while removing the area on the second wafer side, but this is actually very difficult. In addition, when cutting the second wafer with a cutting blade, there is also a problem that cutting water penetrates from the cutting groove of the second wafer to the first wafer side, resulting in a deterioration in device quality.

[0006] The present invention has been made in consideration of the above-mentioned facts, and its main technical object is to provide a processing method for stacked wafers that does not cause a decrease in quality, even when the area corresponding to the planned dividing line is removed from the second wafer to expose the planned dividing line formed on the surface of the first wafer. [Means for solving the problem]

[0007] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a method for processing a stacked wafer in which a second wafer is stacked on a surface of a first wafer having a plurality of devices partitioned and formed on a surface thereof by a dividing line, the method comprising: a modified layer forming step of irradiating the second wafer with a focused point of a laser beam having a transparent wavelength positioned inside two sides that define the dividing line from an upper surface side of the second wafer to form at least two modified layers on the second wafer along the dividing line; a tape adhering step of adhering a tape to the upper surface of the second wafer; and a dividing line exposing step of peeling the tape from the upper surface of the second wafer to remove from the second wafer an end material corresponding to the dividing line on which the modified layer has been formed along the dividing line, thereby exposing the dividing line formed on the surface of the first wafer. and a thinning step of thinning the upper surface of the second wafer by grinding or polishing the upper surface of the second wafer before the modified layer forming step. A method for processing stacked wafers is provided. Further, according to the present invention, there is provided a method for processing stacked wafers in which a second wafer is stacked on a surface of a first wafer having a plurality of devices formed on the surface and partitioned by a planned dividing line, the method including a modified layer forming step of irradiating the second wafer with a focal point of a laser beam having a transparent wavelength positioned inside two sides that define the planned dividing line from the upper surface side of the second wafer to form at least two modified layers on the second wafer along the planned dividing line, a tape adhering step of adhering a tape to the upper surface of the second wafer, and a dividing line exposing step of peeling the tape from the upper surface of the second wafer to remove from the second wafer the scrap material corresponding to the planned dividing line on which the modified layer has been formed along the planned dividing line, thereby exposing the planned dividing line formed on the surface of the first wafer, and a thinning step of grinding or polishing the upper surface of the second wafer to thin it after the modified layer forming step.

[0008] The tape adhering step may include an ultraviolet-curable tape adhering step of adhering an ultraviolet-curable tape, the adhesive strength of which is reduced by irradiation with ultraviolet rays, to the upper surface of the second wafer, and an ultraviolet irradiation step of irradiating an area of ​​the ultraviolet-curable tape other than the area corresponding to the planned division line with ultraviolet rays to reduce the adhesive strength. The tape used in the tape adhering step may be a thermocompression tape containing polyolefin, and the thermocompression tape laid on the upper surface of the second wafer may be heated and pressed to be adhered. Effect of the Invention

[0010] The method for processing stacked wafers of the present invention is a method for processing stacked wafers in which a second wafer is stacked on a surface of a first wafer having a plurality of devices formed on the surface and partitioned by a planned dividing line, and includes a modified layer forming step of irradiating the second wafer with a focused point of a laser beam having a wavelength having transparency from the upper surface side of the second wafer, positioned inside two sides that define the planned dividing line, to form at least two modified layers on the second wafer along the planned dividing line; and a tape attaching step of attaching a tape to the upper surface of the second wafer. Since the method includes a bonding step and a dividing line exposing step of removing the tape from the upper surface of the second wafer and removing from the second wafer the scrap material corresponding to the dividing line where the modified layer has been formed along the dividing line to expose the dividing line formed on the surface of the first wafer, the area corresponding to the dividing line of the first wafer can be removed from the second wafer without using a cutting blade, eliminating the problem of quality degradation caused by the cutting blade coming into contact with the first stacked wafer 1. In addition, since no cutting water is used when removing the area corresponding to the dividing line of the first wafer, the problem of quality degradation caused by cutting water is also eliminated. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is an exploded perspective view of a laminated wafer which is a workpiece of the present embodiment. [Diagram 2] FIG. 1 is a perspective view showing an embodiment of a thinning step. [Diagram 3] FIG. 2 is an overall perspective view of the laser processing device. [Figure 4] FIG. 4 is a perspective view showing an embodiment of a modified layer forming step. [Diagram 5] FIG. 11 is a perspective view showing another embodiment of the thinning step. [Figure 6] FIG. 2 is a perspective view showing an embodiment of an ultraviolet-curing tape application step in the tape application process. [Figure 7] FIG. 2 is a perspective view showing an embodiment of an ultraviolet ray irradiation step in the tape attachment process. [Figure 8] FIG. 11 is a perspective view showing an embodiment of a division line exposing step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a laminated wafer processing method according to the present invention will be described in detail with reference to the accompanying drawings.

[0013] FIG. 1 shows a perspective view of a laminated wafer W, which is a workpiece in this embodiment. The laminated wafer W is a laminated wafer in which a second wafer 20 is laminated on a first wafer 10, as shown in an exploded view at the top of FIG. 1. The first wafer 10 is, for example, a silicon wafer, and as shown in FIG. 1, a plurality of devices 12 are formed on a surface 10a partitioned by a division line 14. The second wafer 20 is, for example, a silicon wafer, like the first wafer 10, and a plurality of devices (not shown) are partitioned by a division line on the surface 20a side facing downward. When the first wafer 10 and the second wafer 20 are laminated, as shown in the figure, the surface 20a side of the second wafer 20 is bonded to the surface 10a of the first wafer 10 to form an integrated wafer. The dividing lines 14 formed on the surface 10a of the first wafer 10 and the dividing lines formed on the surface 20a of the second wafer 20 are formed at corresponding positions. Therefore, when the first wafer 10 and the second wafer 20 are integrated, the positions of the notches formed on both wafers are aligned, and the wafers are bonded together (see the lower part of FIG. 1), and the wafers are stacked and integrated so that the dividing lines 14 of the first wafer 10 and the dividing lines of the second wafer 20 are completely aligned. An oxide film or the like is formed between the first wafer 10 and the second wafer 20, so that the wafers are firmly integrated. As described above, when the stacked wafers W to be processed according to this embodiment are prepared, the processing method described below is carried out.

[0014] When carrying out the laminated wafer processing method of the present embodiment, if necessary, a thinning step of grinding or polishing the upper surface, i.e., the back surface 20b, of the second wafer 20 may be carried out in advance as described below. The thinning step will be described with reference to FIG.

[0015] 2 shows a grinding device 30 used to perform the thinning process (only a part of the device is shown). The grinding device 30 includes a holding means 31 for holding the laminated wafers W, and a grinding means 32 for grinding the laminated wafers W held by the holding means 31.

[0016] The holding means 31 has, for example, a breathable holding surface (not shown) and is connected to a suction source (not shown) so that the holding surface can suction and hold the laminated wafers W. The grinding means 32 has a rotating spindle 34 rotated by a rotation drive mechanism (not shown), a wheel mount 35 attached to the lower end of the rotating spindle 34, and a grinding wheel 36 attached to the lower surface of the wheel mount 35, and a plurality of grinding stones 37 are arranged in an annular shape on the lower surface of the grinding wheel 36.

[0017] The stacked wafers W are transported to the grinding device 30, and are placed on the holding means 31 with the first wafer 10 facing downward and held by suction. As shown in the figure, the stacked wafers W are positioned below the grinding means 32. Next, the rotating spindle 34 of the grinding means 32 is rotated in the direction indicated by the arrow R1 in the figure at, for example, 6000 rpm, while the holding means 31 is rotated in the direction indicated by the arrow R2 at, for example, 300 rpm. Then, while supplying grinding water onto the back surface 20b of the second wafer 20 by a grinding water supplying means (not shown), the grinding wheel 37 is brought into contact with the back surface 20b of the second wafer 20, and the grinding wheel 36 is fed downward at a grinding feed rate of, for example, 1 μm / sec. At this time, grinding can be carried out while measuring the thickness of the stacked wafers W by a contact-type measuring gauge (not shown), and the back surface 20b of the second wafer 20 of the stacked wafers W is ground by a predetermined amount. After the predetermined amount of grinding is completed, cleaning, drying, and other processes are performed as necessary to complete the thinning process. In addition, in the above-mentioned thinning process, when the amount of thinning of the back surface 20b side of the second wafer 20 is small or when the back surface 20b side of the second wafer 20 needs to be processed into a mirror surface, instead of or in addition to the above-mentioned grinding means 32, a polishing device (not shown) may be used to polish and thin the back surface 20b side of the second wafer 20 with a polishing pad or the like. Furthermore, when the thickness of the second wafer 20 is already the desired thickness when the laminated wafer W is formed, the above-mentioned thinning process may be omitted.

[0018] Once the laminated wafers W are prepared, the modified layer forming step described below is carried out. When carrying out the modified layer forming step, as shown in Fig. 3, the laminated wafers W are held on an annular frame F via an adhesive tape T1, and are transported to a laser processing apparatus 1 shown in the figure.

[0019] 3 shows an overall perspective view of a laser processing apparatus 1 suitable for carrying out the processing method of the present invention. The laser processing apparatus 1 includes a holding means 2, a base 3, a moving means 4, a laser beam application means 6, an imaging means 7, and a control means (not shown).

[0020] The holding means 2 includes a rectangular X-axis direction movable plate 2a mounted on the base 3 so as to be movable in the X-axis direction, a rectangular Y-axis direction movable plate 2c mounted so as to be movable in the Y-axis direction along guide rails 2b and 2b on the X-axis direction movable plate 2a, a cylindrical support 2d fixed to the upper surface of the Y-axis direction movable plate 2c, and a rectangular cover plate 2g fixed to the upper end of the support 2d. A chuck table 2e is disposed on the cover plate 2g, which is a circular member extending upward through an elongated hole formed on the cover plate 2g and is configured to be rotatable by a rotation drive means (not shown). The chuck table 2e is provided with a holding surface 2f formed of a porous material having air permeability and defined by the X-axis direction and the Y-axis direction. The holding surface 2f is connected to a suction means (not shown) by a flow path passing through the support 2d. The X-axis direction is the direction indicated by the arrow X in FIG. 3, and the Y-axis direction is the direction indicated by the arrow Y, which is perpendicular to the X-axis direction. The plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

[0021] The moving means 4 includes an X-axis moving means 41 for moving the chuck table 2e of the holding means 2, the laser beam application means 6, and the imaging means 7 relatively in the X-axis direction, and a Y-axis moving means 42 for moving the chuck table 2e of the holding means 2 and the imaging means 7 relatively in the Y-axis direction. The X-axis moving means 41 includes a ball screw 44 extending in the X-axis direction on the base 3, and a motor 43 connected to one end of the ball screw 44. A nut portion (not shown) of the ball screw 44 is formed on the lower surface of the X-axis direction movable plate 2a. The X-axis moving means 41 converts the rotational motion of the motor 43 into linear motion by the ball screw 44 and transmits it to the X-axis direction movable plate 2a, and moves the X-axis direction movable plate 2a forward and backward in the X-axis direction along the guide rails 3a, 3a on the base 3. The Y-axis moving means 42 includes a ball screw 46 extending in the Y-axis direction on the X-axis direction movable plate 2a, and a motor 45 connected to one end of the ball screw 46. A nut portion (not shown) of the ball screw 46 is formed on the lower surface of the Y-axis direction movable plate 2c. The Y-axis moving means 42 converts the rotational motion of the motor 45 into linear motion by the ball screw 46 and transmits it to the Y-axis direction movable plate 2c, and moves the Y-axis direction movable plate 2c forward and backward in the Y-axis direction along the guide rails 2b, 2b on the X-axis direction movable plate 2a.

[0022] A frame 5 is erected on the rear side of the holding means 2, and includes a vertical wall 5a extending upward from the upper surface of the base 3 and a horizontal wall 5b extending horizontally. The horizontal wall 5b houses the laser beam application means 6 and an optical system of the imaging means 7. A condenser 6a constituting the laser beam application means 6 is disposed on the lower surface of the tip of the horizontal wall 5b, and the imaging means 7 is disposed at a position spaced apart from the condenser 6a in the X-axis direction. The imaging means 7 includes an infrared irradiation means for emitting infrared rays and an infrared imaging element for capturing infrared rays, in addition to an illumination means for emitting visible light and a normal imaging element for capturing visible light. The above-mentioned laser beam application means 6, the moving means 4, the imaging means 7, etc. are electrically connected to a control means (not shown), and laser processing of the workpiece is performed according to an instruction signal issued from the control means.

[0023] The stacked wafers W transported to the laser processing device 1 are placed on the chuck table 2e of the holding means 2 with the back surface 20b of the second wafer 20 facing upward, and are suction-held via the adhesive tape T1. The stacked wafers W held on the chuck table 2e are moved by the moving means 4 and positioned directly under the imaging means 7 for the alignment step. In the alignment step, the imaging means 7 is used to detect the position of the division line 14 formed on the front surface 10a of the first wafer 10 from the back surface 20b of the second wafer 20. Next, the chuck table 2e is rotated by the above-mentioned rotary drive means to align the division line 14 in the X-axis direction. As described above, the first wafer 10 and the second wafer 20 are stacked so that the dividing lines 14 of the first wafer 10 coincide with the dividing lines (not shown) formed on the front surface 20a of the second wafer 20, and therefore the dividing lines of the second wafer 20 are aligned in the X-axis direction together with the dividing lines 14 of the first wafer 10 by the alignment process. Position information of the dividing lines 14 detected by the alignment process is stored in a control means (not shown).

[0024] Based on the position information detected by the above-mentioned alignment step, the condenser 6a of the laser beam application means 6 is positioned above the processing start position corresponding to the predetermined planned dividing line 14, and a modified layer forming step is performed in which a laser beam LB having a wavelength that is transparent to the second wafer 20 is applied to form a modified layer 100 inside the second wafer 20, as shown in Fig. 4(a). This modified layer forming step will be described in more detail with reference to Fig. 4.

[0025] In the modified layer forming step in this embodiment, the focal point of the laser beam LB is positioned inside the second wafer 20, and in a region sandwiched between two sides (14a, 14a) of the adjacent devices 12 that define the planned dividing line 14 of the first wafer 10 when viewed in a plan view as shown in FIG. 4(b). Then, together with the above-mentioned chuck table 2e, the laminated wafer W is processed and fed in the X-axis direction shown in FIG. 4(a) to form the modified layer 100 inside the second wafer 20 along the planned dividing line 14 of the wafer W. Furthermore, in this embodiment, when the focal point of the laser beam LB is positioned inside the two sides to form the modified layer 100, at least two modified layers 102, 104 are formed along the two sides as shown in FIG. 4(b), resulting in a modified layer 100 consisting of two lines including the modified layers 102, 104. In this embodiment, as shown in FIG. 4(c), when the modified layers 102, 104 are formed, the modified layers are formed at a plurality of positions at different depths along the modified layers 102, 104.

[0026] As described above, when the modified layer 100 including the two modified layers 102, 104 is formed in the region inside the second wafer 20 corresponding to the predetermined dividing line 14 along the X-axis direction, the moving means 4 described above is operated to index and feed the stacked wafers W in the Y-axis direction, and the region corresponding to the adjacent unprocessed dividing line 14 in the Y-axis direction is positioned directly under the collector 6a. Then, in the same manner as described above, the focusing point of the laser beam LB is positioned in the region inside the second wafer 20 of the stacked wafers W corresponding to the dividing line 14 and irradiated, and the stacked wafers W are processed and fed in the X-axis direction to form the modified layer 100 including the two modified layers 102, 104. Similarly, the stacked wafers W are processed and fed in the X-axis direction and the Y-axis direction to form the modified layer 100 along all the dividing lines 14 along the X-axis direction inside the second wafer 20. Next, the stacked wafers W are rotated 90 degrees to align the unprocessed dividing lines 14 in a direction perpendicular to the direction along which the modified layers 100 have already been formed with the X-axis direction. Then, the focal point of the laser beam LB is positioned and irradiated in the same manner as described above into the interior of the regions of the second wafer 20 corresponding to the remaining dividing lines 14, forming modified layers 100 including two modified layers 102, 104 along the regions corresponding to all of the dividing lines 14, thereby completing the modified layer forming step.

[0027] The laser processing conditions when carrying out the modified layer forming step are set, for example, as follows. Wavelength: 1064nm Average power output: 1.0W Repetition frequency: 100kHz Machining feed speed: 100mm / sec

[0028] In the modified layer formation process of the above embodiment, the second wafer 20 is positioned inside the two sides 14a, 14a that define the planned division line 14 of the first wafer 10 and irradiated from the top surface (rear surface 20b) side to form a modified layer 100 including two modified layers 102, 104 along the planned division line 14, but the present invention is not limited to this, and it is also possible to form a modified layer including, for example, three or more modified layers.

[0029] In the above embodiment, the thinning step for thinning the back surface 20b of the second wafer 20 is performed before the modified layer forming step is performed, but the present invention is not limited to this, and may be performed after the modified layer forming step. For example, as shown in FIG. 5, the laminated wafer W subjected to the modified layer forming step is transported to a grinding device 30, and the back surface 20b of the second wafer 20 is ground by the same procedure as the thinning step, and grinding or polishing is performed until the desired thickness is obtained. In this way, by performing the thinning step after performing the modified layer forming step, an external force is applied to the region where the modified layer 100 is formed, and the second wafer 20 is divided along the modified layer 100 (modified layers 102, 104), and a fracture region 110 is formed. The region divided along the modified layer 100 by the thinning step is extremely narrow, and the grinding water used in the grinding does not infiltrate into the first wafer 10 side. In the embodiment described below, the thinning step is performed before the modified layer forming step.

[0030] After the above-mentioned modified layer forming step is performed, a tape adhering step is performed in which an adhesive tape is adhered to the upper surface (rear surface 20b) of the second wafer 20. When performing the tape adhering step, a tape T2 having approximately the same dimensions as the laminated wafer W in a plan view is prepared as shown in FIG. 6. The tape T2 to be adhered is not particularly limited, but in this embodiment, for example, an ultraviolet curing tape that is hardened by reducing its adhesive force when irradiated with ultraviolet light is selected. As the ultraviolet curing tape, for example, an ultraviolet curing tape having a polyvinyl chloride (PVC) base material can be adopted. After the above-mentioned tape T2 is prepared, an ultraviolet curing tape adhering step is performed in which the tape T2 is adhered to the rear surface 20b of the second wafer 20 of the laminated wafer W on which the modified layer 100 is formed, as shown in the figure, to integrate the two.

[0031] When an ultraviolet-curing tape is used as the above-mentioned tape T2, it is preferable to carry out an ultraviolet irradiation step as shown in FIG.

[0032] When performing the ultraviolet ray irradiation step, as shown in FIG. 7, a mask member 120 is placed on the tape T2 of the laminated wafer W held by the adhesive tape T1. The mask member 120 includes an annular frame 122 having an opening 122a corresponding to the shape of the laminated wafer W, and a lattice member 124 that masks an area corresponding to the division lines 14 of the tape T2 attached to the laminated wafer W inside the opening 122a. By placing the mask member 120 on the tape T2 of the laminated wafer W held by the adhesive tape T1, an area corresponding to the division lines 14 on the tape T2 in a plan view is masked by the lattice member 124. With the mask member 120 placed on the adhesive tape T1 in this way, the ultraviolet ray irradiation device 50 is positioned above, and ultraviolet rays P are irradiated from the ultraviolet ray irradiation surface 50a to at least the entire area of ​​the mask member 120. As a result, the ultraviolet rays P are irradiated onto the areas of the tape T2 other than the areas corresponding to the division lines 14, and the adhesive strength of the areas other than the areas corresponding to the division lines 14 is reduced.

[0033] As described above, after the tape adhering process including the ultraviolet curing tape adhering step and the ultraviolet ray irradiation step has been carried out, the division line exposing step described below is carried out.

[0034] The dividing line exposure step is performed by peeling the tape T2 attached to the back surface 20b of the second wafer 20 of the laminated wafers W upward (in the direction indicated by the arrow R3) as shown in FIG. 8. At this time, the adhesive strength of the region T2a irradiated with ultraviolet light in the ultraviolet light irradiation step described above is reduced, and the region T2a is easily peeled off from the back surface 20b of the second wafer 20. In contrast, the adhesive strength of the region T2b masked by the lattice member 124 of the mask member 120 in the ultraviolet light irradiation step described above is not reduced, and the region corresponding to the dividing line 14 of the first wafer 10 has the two modified layers 102, 104 formed to be the starting points of fracture as described above, so that the region corresponding to the dividing line 14 of the second wafer 20 is separated into scraps 22. As a result, the scrap material 22 corresponding to the intended dividing line 14, along which modified layers 102, 104 have been formed, can be removed from the second wafer 20, and the intended dividing line 14 formed on the surface 10a of the first wafer 10 can be exposed.

[0035] According to the above-described embodiment, in the method for processing stacked wafers, the areas corresponding to the planned dividing lines 14 of the first wafer 10 can be removed from the second wafer 20 without using a cutting blade, eliminating the problem of quality degradation caused by the cutting blade coming into contact with the first stacked wafer 10. In addition, since no cutting water is used when removing the areas corresponding to the planned dividing lines 14 of the first wafer 10, the problem of quality degradation caused by cutting water is also eliminated.

[0036] In the above embodiment, an ultraviolet-curable tape is used as the tape T2 to be applied in the tape application step, and an ultraviolet-curable tape application step and an ultraviolet irradiation step are performed, but the present invention is not limited to this. For example, a thermocompression tape containing polyolefin may be used as the tape T2 used in the tape application step, and the thermocompression tape laid on the upper surface of the second wafer 20 may be heated and pressed to be applied. In this case, as described above, the tape T2 is subsequently peeled off from the upper surface (back surface 20b) of the second wafer 20, and the end material 22 corresponding to the division lines 14 on which the modified layers 102, 104 are formed along the division lines 14 is removed from the second wafer 20, thereby exposing the division lines 14 formed on the front surface 10a of the first wafer 10. [Explanation of symbols]

[0037] 1: Laser processing equipment 2: Holding means 2a: X-axis movable plate 2b: Guide rail 2c: Y-axis movable plate 2d: Post 2e: Chuck table 2f: Holding surface 2g: Cover plate 3: Base 4. Transportation 41:X-axis movement means 42: Y-axis movement means 43, 45: Motor 44, 46: Ball screw 5:Frame body 5a: Vertical wall 5b:Horizontal wall part 6: Laser beam irradiation means 6a: Concentrator 7: Imaging means 10: First wafer 10a: surface 10b: Back side 12: Device 14: Planned division line 20: Second wafer 20a: Surface 20b: Back side 30: Grinding equipment 31: Holding means 32: Grinding means 36: Grinding wheel 37: Grinding wheel 50: Ultraviolet irradiation device 50a: UV irradiation surface 100: Modified layer 102, 104: Modified layer 120: Mask material 122: Circular frame 124: Lattice member T1: Adhesive tape T2: Tape W: Stacked wafer

Claims

1. A method for processing a laminated wafer in which a second wafer is laminated on a surface of a first wafer having a plurality of devices formed on the surface by partitioning the first wafer by planned division lines, comprising the steps of: a modified layer forming step of irradiating the second wafer with a laser beam having a wavelength having transparency from the upper surface side of the second wafer by positioning a focal point of the laser beam within two sides that define the planned dividing line, thereby forming at least two modified layers on the second wafer along the planned dividing line; a tape application step of applying a tape to an upper surface of the second wafer; a dividing line exposing step of removing the tape from the upper surface of the second wafer to remove from the second wafer an end material corresponding to the dividing line along which the modified layer is formed, thereby exposing the dividing line formed on the surface of the first wafer; Including, The laminated wafer processing method includes a thinning step of grinding or polishing the upper surface of the second wafer to thin it before the modified layer forming step.

2. A method for processing a stacked wafer, comprising stacking a second wafer on a surface of a first wafer having a plurality of devices formed on the surface of the first wafer partitioned by planned division lines, the method comprising: a modified layer forming step of irradiating the second wafer with a laser beam having a wavelength having transparency from the upper surface side of the second wafer by positioning a focal point of the laser beam within two sides that define the planned dividing line, thereby forming at least two modified layers on the second wafer along the planned dividing line; a tape application step of applying a tape to an upper surface of the second wafer; a dividing line exposing step of removing the tape from the upper surface of the second wafer to remove from the second wafer an end material corresponding to the dividing line along which the modified layer is formed, thereby exposing the dividing line formed on the surface of the first wafer; Including, The laminated wafer processing method further comprises, after the modified layer forming step, a thinning step of grinding or polishing the upper surface of the second wafer to thin it.

3. A method for processing a laminated wafer as described in claim 1 or 2, wherein the tape application process includes an ultraviolet-curing tape application step of applying an ultraviolet-curing tape, the adhesive strength of which decreases when irradiated with ultraviolet light, to the upper surface of the second wafer, and an ultraviolet irradiation step of irradiating ultraviolet light to areas of the ultraviolet-curing tape other than the areas corresponding to the planned division lines to reduce the adhesive strength.

4. A method for processing laminated wafers as described in claim 1 or 2, in which the tape used in the tape application step is a thermo-compression tape containing polyolefin, and the thermo-compression tape laid on the upper surface of the second wafer is heated and pressed to apply the tape.

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