Wafer processing method

Abstract

To provide a wafer processing method that can suppress detachment of a portion of an outer peripheral surplus area surrounding a device area during grinding of a bonded wafer.SOLUTION: A wafer processing method includes a bonding wafer forming step 101 of bonding one surface of a first wafer having a device area and an outer peripheral surplus area on one surface to one surface of a second wafer to form a bonding wafer, a dividing step 102 of forming a plurality of annular modified layers along an outer peripheral edge of the device area of the first wafer in a thickness direction by a laser beam, and diving annular modified layers into an outer peripheral annular portion corresponding to the outer peripheral surplus area and a central region corresponding to the device region, an outer peripheral annular portion separation step 103 of peeling off the outer peripheral annular portion from the second wafer and separating the outer peripheral annular portion from the second wafer by applying ultrasonic waves to the bonded wafer immersed in liquid, and a grinding step 104 of grinding the first wafer from the other surface to a finish thickness.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a wafer processing method. [Background technology]

[0002] TSV (Through-Silicon Via) wafers enable the connection of the electrodes of two chips by bonding them together using through-hole electrodes. For example, 3D NAND flash memory is manufactured using this technology. TSV wafers are ground to thin them down to reduce their back surface, but in this case, they are ground while still bonded to a support wafer (silicon, glass, ceramics, etc.) that serves as the base.

[0003] Usually, the outer peripheral side of a wafer is chamfered to have an R-shape, so when the wafer is ground to an extremely thin thickness, the outer peripheral side of the wafer becomes a so-called knife edge, and the edge is likely to chip during grinding. If the edge chips during grinding, the chips may extend to the device and cause damage to the device. As a countermeasure against this, a so-called edge trimming technique has been developed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4895594 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the edge trimming technology shown in Patent Document 1 has a problem that chipping that reaches the device and damages the device occurs when cutting the outer periphery of the front side of the wafer in a ring shape. In addition, there is a problem that a large amount of cutting waste is generated, so the device is easily contaminated. In addition, a method has been devised to prevent the edge chipping of the wafer that occurs during grinding from extending to the device by forming a modified layer with a laser beam along the outer periphery of the device area after bonding the wafers, but the problem remains that the outer periphery excess area breaks off in a ring or arc shape during grinding and accumulates in the processing chamber of the grinding device.

[0006] The present invention has been made in consideration of such problems, and its object is to provide a wafer processing method that can suppress the detachment of a portion of the outer peripheral excess region surrounding the device region during grinding of a bonded wafer. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the wafer processing method of the present invention includes a bonded wafer forming step of bonding one surface of a first wafer, the one surface of which has a device region in which devices are formed and a peripheral excess region surrounding the device region and has a chamfered peripheral edge, to one surface of a second wafer to form a bonded wafer; irradiating a laser beam of a wavelength that is transparent to the first wafer along the peripheral edge of the device region of the first wafer of the bonded wafer, to form a plurality of annular modified layers along the peripheral edge in the thickness direction of the wafer, and bonding the first wafer in a state bonded to the second wafer to form a peripheral annular portion corresponding to the peripheral excess region and the device region. a dividing step of dividing the first wafer into a first region and a second region corresponding to the first region, a peripheral annular portion separating step of peeling the peripheral annular portion from the second wafer by applying ultrasonic waves to the bonded wafer immersed in a liquid through the liquid or by supplying a chemical liquid to an interface at the outer periphery of the bonded wafer after the dividing step, and a grinding step of grinding the first wafer from the other surface to thin the first wafer to a finish thickness after the peripheral annular portion separating step, wherein the first wafer and the second wafer are TSV wafers, and the device includes an electrode pad provided on one surface of the device, and a through electrode having one end connected to the electrode pad and the other end extending toward the other surface. and in the dividing step, a position of at least one of the modified layers formed in the thickness direction is a position in the thickness direction between the one end and the other end of the through electrode. It is characterized by the above.

[0008] The dividing step may further include a preliminary dividing step of, after dividing the outer peripheral annular portion and the central region, irradiating the outer peripheral annular portion with the laser beam to form a plurality of modified layers in the thickness direction of the first wafer, and dividing the outer peripheral annular portion into a plurality of arc-shaped portions. Preferably, in the preliminary cutting step, the position of at least one of the modified layers formed in the thickness direction is a position in the thickness direction between the one end and the other end of the through electrode. stomach.

[0009] The dividing step may further include an interface processing step of irradiating a laser beam having a wavelength that is transparent to the first wafer or the second wafer along the interface where the first wafer and the second wafer are bonded together in the outer peripheral annular portion, to form a modified layer at the interface, which will serve as a starting point for peeling. Effect of the Invention

[0010] The present invention can suppress separation of a portion of the outer circumferential excess region surrounding the device region during grinding of the bonded wafer. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing an example of a wafer to be processed by a wafer processing method according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the wafer shown in FIG. [Diagram 3] FIG. 3 is an enlarged perspective view of a device on the wafer shown in FIG. [Figure 4] FIG. 4 is a flowchart showing a flow of the wafer processing method according to the embodiment. [Diagram 5] FIG. 5 is a perspective view showing one state of the bonded wafer forming step shown in FIG. [Figure 6] FIG. 6 is a perspective view showing a state after FIG. 5 in the bonded wafer forming step shown in FIG. [Figure 7] FIG. 7 is a cross-sectional view of the wafer shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view that illustrates one state of the dividing step illustrated in FIG. [Figure 9] FIG. 9 is a cross-sectional view that illustrates one state of the preliminary cutting step in the cutting step illustrated in FIG. [Figure 10] FIG. 10 is a plan view that illustrates the wafer after the preliminary cutting step. [Figure 11] FIG. 11 is a cross-sectional view that illustrates one state of an interface processing step in the dividing step illustrated in FIG. [Figure 12] FIG. 12 is a plan view that typically shows the wafer after the interface processing step. [Figure 13] FIG. 13 is a cross-sectional view that illustrates an example of the outer circumferential annular portion removing step illustrated in FIG. [Figure 14]FIG. 14 is a cross-sectional view that illustrates an example of the grinding step illustrated in FIG. [Figure 15] FIG. 15 is a plan view that illustrates the wafer after the grinding step illustrated in FIG. [Figure 16] FIG. 16 is a cross-sectional view that illustrates an example of an outer circumferential annular portion removing step in a wafer processing method according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0013] [Embodiment] A method for processing a wafer 10 according to an embodiment of the present invention will be described with reference to the drawings. First, the configuration of the wafer 10, which is the object of processing in the embodiment, will be described. FIG. 1 is a perspective view showing an example of the wafer 10, which is the object of processing in the method for processing a wafer 10 according to the embodiment. FIG. 2 is a cross-sectional view of the wafer 10 shown in FIG. 1. FIG. 3 is an enlarged perspective view showing a device 18 of the wafer 10 shown in FIG. 1.

[0014] As shown in Fig. 1, the wafer 10 is a disk-shaped semiconductor wafer, an optical device wafer, or the like, with a substrate 11 made of silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), or the like. The wafer 10 has a chamfered outer periphery 12. In the embodiment, the outer periphery 12 of the wafer 10 is formed in a cross-sectional arc shape extending from a front surface 13 to a back surface 14 of the substrate 11 such that the center in the thickness direction protrudes most toward the outer periphery. The wafer 10 also includes a device region 15 on the front surface 13 side of the substrate 11, and an outer periphery excess region 16 surrounding the device region 15.

[0015] The device region 15 has a plurality of planned division lines 17 set in a grid pattern on the surface 13 of the substrate 11, and devices 18 formed in each region partitioned by the planned division lines 17. The peripheral surplus region 16 is a region that surrounds the device region 15 all around and in which no devices 18 are formed.

[0016] In the embodiment, the device 18 constitutes a 3D NAND flash memory, but the present invention is not limited thereto. As shown in Fig. 3, the device 18 includes an electrode pad 19 and a through electrode 20 connected to the electrode pad 19. At least one electrode pad 19 (in the embodiment, a plurality of electrode pads 19) is provided on the surface of the device 18.

[0017] In the embodiment, the through electrodes 20 are provided in one-to-one correspondence with the electrode pads 19. One end of the through electrodes 20 is connected to the corresponding electrode pads 19, extends from the corresponding electrode pads 19 toward the rear surface 14 of the substrate 11, and is embedded in the substrate 11. Note that the length from the front surface 13 of the substrate 11 to the other end of the through electrodes 20 is equal to the finished thickness 21 of the wafer 10 in the embodiment, but may be longer than the finished thickness 21 in the present invention.

[0018] The through electrodes 20 penetrate the back surface 14 of the substrate 11 when the substrate 11 is thinned and the devices 18 are individually separated from the wafer 10. The wafer 10 of the embodiment is a so-called TSV wafer in which the individually separated devices 18 have through electrodes. Note that the wafer of the present invention is not limited to a TSV wafer having through electrodes as in the embodiment, and may be a device wafer without through electrodes.

[0019] Next, a processing method of the wafer 10 according to the embodiment will be described. The processing method of the wafer 10 according to the embodiment is a method of bonding the front surface 13 sides of a pair of wafers 10 to each other and thinning one of the wafers 10 (wafer 10-1) to a finishing thickness 21. In the following description, when the wafers 10 of the pair of wafers 10 are to be distinguished from each other, the one wafer 10 is referred to as a first wafer 10-1 and the other wafer 10 is referred to as a second wafer 10-2. When there is no distinction, the other wafer 10-2 is simply referred to as a wafer 10. In the embodiment, the other wafer 10-2 that is not thinned is a TSV wafer similar to the wafer 10-1, but in the present invention, it may be a simple substrate wafer without a pattern. FIG. 4 is a flowchart showing the flow of the processing method of the wafer 10 according to the embodiment. The processing method of the wafer 10 includes a bonded wafer forming step 101, a dividing step 102, an outer circumferential ring part removing step 103, and a grinding step 104.

[0020] (Bonded wafer formation step 101) FIG. 5 is a perspective view showing one state of the bonded wafer forming step 101 shown in FIG. 4. FIG. 6 is a perspective view showing one state of the bonded wafer forming step 101 shown in FIG. 4 after FIG. 5. FIG. 7 is a cross-sectional view of the wafer 10 shown in FIG. 6. The bonded wafer forming step 101 is a step of bonding one surface of a first wafer 10-1 to one surface of a second wafer 10-2 to form a bonded wafer 1. In the bonded wafer forming step 101 of the embodiment, a surface 13 of the first wafer 10-1 is bonded to a surface 13 of the second wafer 10-2.

[0021] In the bonded wafer formation step 101, an adhesive layer 22 is laminated on one of the front surface 13 of the first wafer 10-1 and the front surface 13 of the second wafer 10-2. In the embodiment, the adhesive layer 22 is laminated on the front surface 13 of the second wafer 10-2. Note that, although the adhesive layer 22 is a double-sided tape having adhesive layers laminated on the front and back surfaces of a base layer in the embodiment, the adhesive layer 22 is not limited to the double-sided tape in the present invention and may be, for example, an oxide film.

[0022] In the bonded wafer forming step 101, first, the surface 13 of the first wafer 10-1 and the surface 13 of the second wafer 10-2 are opposed to each other with a gap therebetween, as shown in Fig. 5. Next, the surface 13 of the first wafer 10-1 and the surface 13 of the second wafer 10-2 are bonded together, as shown in Fig. 6 and Fig. 7. In this way, the bonded wafer 1 is formed.

[0023] (Dividing step 102) Fig. 8 is a cross-sectional view showing a schematic diagram of one state of the dividing step 102 shown in Fig. 4. The dividing step 102 is carried out after the bonded wafer forming step 101. The dividing step 102 is a step of dividing the first wafer 10-1 in a state where the first wafer 10-1 is bonded to the second wafer 10-2 of the bonded wafer 1 into an outer circumferential annular portion corresponding to the outer circumferential excess region 16 and a central region corresponding to the device region 15.

[0024] In the dividing step 102, a laser beam 30 is applied to a position where the outer peripheral annular portion and the central region of the first wafer 10-1 are to be divided, to form a modified layer 23 that serves as a separation starting point. The laser beam 30 is a laser beam having a wavelength that is transparent to the first wafer 10-1 of the bonded wafer 1. The modified layer 23 means a region in which the density, refractive index, mechanical strength or other physical properties are different from those of the surrounding area. The modified layer 23 is, for example, a melting process region, a crack region, a dielectric breakdown region, a refractive index change region, a region where these regions are mixed, etc. The modified layer 23 has a lower mechanical strength, etc. than other parts of the wafer 10.

[0025] In the dividing step 102, a modified layer 23 is formed on the first wafer 10-1 by stealth dicing using a laser processing device 35. The laser processing device 35 includes a chuck table 36, a laser beam application unit 38 that irradiates a laser beam 30 toward the wafer 10 held on a holding surface 37 of the chuck table 36, and a moving unit that moves the chuck table 36 and the laser beam application unit 38 relatively.

[0026] In the dividing step 102, first, the back surface 14 side of the second wafer 10-2 of the bonded wafer 1 is sucked and held on the holding surface 37 of the chuck table 36, and then the moving unit moves the chuck table 36 to a processing position. Next, the laser beam application unit 38 is vertically opposed from the back surface 14 side of the first wafer 10-1 toward the outer periphery of the device region 15, and then the focal point 31 of the laser beam 30 is set inside the first wafer 10-1.

[0027] In the dividing step 102, the first wafer 10-1 is then irradiated with a laser beam 30 from a laser beam application unit 38 while rotating the chuck table 36 about an axis parallel to the vertical direction. That is, the laser beam 30 is irradiated along the outer periphery of the device region 15 of the first wafer 10-1 to form a continuous dotted modified layer 23 in an annular shape along the outer periphery.

[0028] In this case, in the dividing step 102, the height of the focal point 31 of the laser beam 30 is changed and the laser beam 30 is irradiated multiple times, or a laser beam having multiple focal points spaced apart in the thickness direction of the first wafer 10-1 is irradiated, thereby forming multiple modified layers 23 in the thickness direction of the first wafer 10-1. Cracks extend from the modified layer 23, and the first wafer 10-1 is divided into an outer peripheral annular portion corresponding to the outer peripheral excess region 16 and a central region corresponding to the device region 15 by connecting the modified layer 23 and the crack. In the dividing step 102 of the embodiment, a preliminary dividing step and an interface processing step described below are further performed. In the dividing step 102, it is sufficient to form at least the modified layer 23 shown in FIG. 8 and divide the first wafer 10-1 into an outer peripheral annular portion and a central region, and in the present invention, both the preliminary dividing step and the interface processing step described below may not be performed.

[0029] (Preliminary cutting step) Fig. 9 is a cross-sectional view showing a state of the preliminary cutting step in the cutting step 102 shown in Fig. 4. Fig. 10 is a plan view showing the wafer 10 after the preliminary cutting step. The preliminary cutting step is a step of cutting the outer peripheral annular portion into a plurality of arc-shaped portions after the outer peripheral annular portion and the central region are cut.

[0030] In the preliminary cutting step, first, the laser beam application unit 38 is vertically opposed from the back surface 14 side of the first wafer 10-1 toward a predetermined position on the outer periphery of the device region 15, and then the focal point 31 of the laser beam 30 is set inside the first wafer 10-1.

[0031] In the preliminary cutting step, the laser beam 30 is irradiated onto the first wafer 10-1 from the laser beam application unit 38 while the chuck table 36 and the laser beam application unit 38 are moved relatively by the moving unit. At this time, the chuck table 36 is moved so that the focal point 31 of the laser beam 30 moves toward the radially outer side of the first wafer 10-1. That is, the laser beam 30 is irradiated in the radial direction onto the outer circumferential annular portion corresponding to the outer circumferential excess region 16, thereby forming a dotted modified layer 24 that is continuous in the radial direction.

[0032] In this case, in the preliminary cutting step, the height of the focal point 31 of the laser beam 30 is changed and the laser beam 30 is irradiated multiple times, or a laser beam having multiple focal points spaced apart in the thickness direction of the first wafer 10-1 is irradiated, thereby forming multiple modified layers 24 in the thickness direction of the first wafer 10-1. Cracks extend from the modified layers 24, and the peripheral annular portion corresponding to the peripheral excess region 16 of the first wafer 10-1 is cut into multiple arc-shaped portions by connecting the modified layers 24 with the cracks.

[0033] (Interface processing step) Fig. 11 is a cross-sectional view showing a schematic state of an interface processing step in the dividing step 102 shown in Fig. 4. Fig. 12 is a plan view showing a schematic state of the wafer 10 after the interface processing step. The interface processing step is a step of forming a modified layer 25, which becomes a peeling starting point, at the interface where the first wafer 10-1 and the second wafer 10-2 are bonded together.

[0034] In the interface processing step, first, the laser beam application unit 38 is vertically opposed from the back surface 14 side of the first wafer 10-1 toward a predetermined position in the peripheral excess region 16, and then the focal point 31 of the laser beam 30 is set at the interface between the first wafer 10-1 and the second wafer 10-2.

[0035] In the interface processing step, next, the chuck table 36 is rotated around an axis parallel to the vertical direction while the laser beam 30 is irradiated from the laser beam application unit 38 onto the interface between the first wafer 10-1 and the second wafer 10-2. That is, the laser beam 30 is irradiated along a predetermined radial position of the outer peripheral excess region 16 of the first wafer 10-1 to form a continuous dotted modified layer 25 in an annular shape.

[0036] In the interface processing step, the position of the focal point 31 of the laser beam 30 is then changed in the radial direction of the wafer 10 to irradiate the wafer with the laser beam 30 multiple times, or a laser beam having multiple focal points in the radial direction is irradiated to form multiple modified layers 25 in the radial direction of the interface. This separates the outer circumferential annular portion corresponding to the outer circumferential excess region 16 of the first wafer 10-1 from the second wafer 10-2 along the interface.

[0037] In the embodiment, in the cutting step 102, the preliminary cutting step and the interface processing step, the laser beam 30 is irradiated from the back surface 14 side of the first wafer 10-1, but in the present invention, the laser beam 30 may be irradiated from the back surface 14 side of the second wafer 10-2.

[0038] (Outer Circumferential Ring Section Removal Step 103) Fig. 13 is a cross-sectional view showing a schematic example of the outer circumferential annular portion separating step 103 shown in Fig. 4. The outer circumferential annular portion separating step 103 is performed after the dividing step 102. The outer circumferential annular portion separating step 103 is a step of peeling the outer circumferential annular portion of the first wafer 10-1 from the second wafer 10-2 and separating it from the bonded wafer 1.

[0039] In the outer circumferential ring-shaped portion detaching step 103 of the embodiment, the outer circumferential ring-shaped portion of the first wafer 10-1 is detached from the second wafer 10-2 by applying ultrasonic waves to the bonded wafer 1 immersed in the liquid 40 through the liquid 40. The liquid 40 is, for example, pure water or a chemical solution containing hydrofluoric acid or the like.

[0040] In the outer circumferential annular portion removing step 103 of the embodiment, first, the bonded wafer 1 is immersed inside a container 41 filled with a liquid 40. At this time, in the embodiment, the bonded wafer 1 is placed on a mounting surface 43 of an ultrasonic vibration source 42 provided on the bottom surface of the container 41.

[0041] Next, the ultrasonic vibration source 42 is driven to generate ultrasonic waves. As a result, ultrasonic waves are applied to the bonded wafer 1 through the liquid 40. When ultrasonic waves are applied to the bonded wafer 1, the outer circumferential annular portion corresponding to the outer circumferential excess region 16 of the first wafer 10-1 is peeled off from the second wafer 10-2.

[0042] Specifically, the outer circumferential ring portion of the first wafer 10-1 is peeled off from the second wafer 10-2, with the modified layer 25 formed at the interface between the first wafer 10-1 and the second wafer 10-2 as the separation starting point. Then, with the modified layers 23 and 24 as the separation starting points, each of the arc-shaped portions of the outer circumferential ring portion of the first wafer 10-1 is detached from the central region corresponding to the device region 15 of the first wafer 10-1.

[0043] (Grinding step 104) Fig. 14 is a cross-sectional view showing an example of the grinding step 104 shown in Fig. 4. Fig. 15 is a plan view showing the wafer 10 after the grinding step 104 shown in Fig. 4. The grinding step 104 is performed after the outer circumferential annular portion removing step 103. The grinding step 104 is a step of grinding the first wafer 10-1 from the other surface to thin it down to the finishing thickness 21. In the grinding step 104 of the embodiment, grinding is performed from the back surface 14 of the first wafer 10-1.

[0044] In the grinding step 104, the back surface 14 of the first wafer 10-1 held on the holding surface 52 of the chuck table 51 is ground by a grinding device 50. The grinding device 50 includes the chuck table 51, a spindle 53 which is a rotating shaft member, a grinding wheel 54 attached to the lower end of the spindle 53, a grinding stone 55 attached to the lower surface of the grinding wheel 54, and a grinding water supply unit 56. The grinding wheel 54 rotates on an axis parallel to the axis of the chuck table 51.

[0045] In the grinding step 104, first, the back surface 14 side of the second wafer 10-2 of the bonded wafer 1 is suction-held on the holding surface 52 of the chuck table 51. Next, while the chuck table 51 is rotated about its axis, the grinding wheel 54 is rotated about its axis. Grinding water 57 is supplied from the grinding water supply unit 56, and the grinding wheel 55 of the grinding wheel 54 is brought closer to the chuck table 51 at a predetermined feed rate, whereby the back surface 14 of the first wafer 10-1 is ground by the grinding wheel 55.

[0046] In the grinding step 104, the grinding device 50 grinds and thins the first wafer 10-1 to the finishing thickness 21. In the grinding step 104, when the grinding device 50 grinds and thins the first wafer 10-1 to the finishing thickness 21, the other end of the through electrode 20 is exposed or about to be exposed on the back surface 14 side. Note that FIG. 14 omits the devices 18 and through electrodes 20 of the second wafer 10-2, and FIG. 15 omits the other end of the through electrode 20.

[0047] As described above, in the processing method for the wafer 10 according to each embodiment, after forming the bonded wafer 1, the modified layers 23, 24, 25 that become the separation starting points are formed by the laser beam 30, so there is less risk of cutting debris adhering to the device 18 compared to edge trimming during cutting. Also, since the outer circumferential surplus region 16 portion is detached from the bonded wafer 1 before grinding to the finishing thickness 21, there is an effect that the outer circumferential surplus region 16 portion will not detach during grinding and accumulate in the processing chamber.

[0048] The present invention is not limited to the above embodiment. In other words, various modifications can be made without departing from the gist of the present invention. For example, the outer circumferential ring portion removing step 103 of the processing method of the wafer 10 may be performed as shown in the following modified example.

[0049] 16 is a cross-sectional view showing an example of an outer circumferential ring-shaped portion separating step 103 in the modified example of the processing method for the wafer 10. In the outer circumferential ring-shaped portion separating step 103 in the modified example, a chemical solution 60 is supplied to the interface of the outer circumferential edge 12 of the bonded wafer 1 to separate the outer circumferential ring-shaped portion of the first wafer 10-1 from the second wafer 10-2.

[0050] In the outer circumferential annular portion removing step 103 of the modified example, a chemical liquid 60 is supplied to the interface of the outer circumferential edge 12 of the bonded wafer 1 by a chemical liquid supply unit 61. The chemical liquid 60 is, for example, hydrofluoric acid.

[0051] In the outer peripheral annular portion detachment step 103 of the modified example, first, the back surface 14 side of the second wafer 10-2 of the bonded wafer 1 is suction-held on the holding surface 63 of the chuck table 62. Next, while the chuck table 62 is rotated about its axis, a chemical liquid 60 is supplied from the radially outer side of the outer peripheral edge 12 of the bonded wafer 1 toward the interface by the chemical liquid supply unit 61. This melts the oxide film at the interface, and the outer peripheral annular portion corresponding to the outer peripheral excess region 16 of the first wafer 10-1 is peeled off from the second wafer 10-2. After the outer peripheral annular portion of the first wafer 10-1 is peeled off, the bonded wafer 1 is washed with pure water or the like. [Explanation of symbols]

[0052] 1 Bonded wafer 10 wafers 10-1 First wafer 10-2 Second wafer 11 Substrate 12 Outer rim 13 Surface 14 Back side 15 Device Area 16 Surplus outer area 17 Division line 18 Devices 19 Electrode Pads 20 Through electrode 21 Finished thickness 22 Adhesive layer 23, 24, 25 Modification layer 30 Laser Beam 40 liquid 50 Grinding Equipment 60 Chemical Solution

Claims

1. a bonded wafer forming step of bonding one surface of a first wafer, the one surface of the first wafer having a device region in which devices are formed and a peripheral excess region surrounding the device region and a chamfered peripheral edge, to one surface of a second wafer to form a bonded wafer; a dividing step of irradiating a laser beam having a wavelength that is transparent to the first wafer of the bonded wafer along an outer periphery of the device region of the first wafer to form a plurality of annular modified layers along the outer periphery in a thickness direction of the wafer, and dividing the first wafer in a state bonded to the second wafer into an outer periphery annular portion corresponding to the outer periphery excess region and a central region corresponding to the device region; an outer circumferential ring-shaped portion separating step of applying ultrasonic waves to the bonded wafer immersed in a liquid through the liquid or supplying a chemical liquid to an interface at an outer circumferential edge of the bonded wafer, thereby peeling the outer circumferential ring-shaped portion from the second wafer and separating the outer circumferential ring-shaped portion from the bonded wafer after the dividing step is performed; a grinding step of grinding the first wafer from the other side thereof to a finish thickness after the outer circumferential annular portion removing step is performed; Equipped with The first wafer and the second wafer are the device is a TSV wafer including an electrode pad provided on one surface of the device, and a through electrode having one end connected to the electrode pad and the other end extending toward the other surface; In the dividing step, a position of at least one of the modified layers formed in the thickness direction is a position in the thickness direction between the one end and the other end of the through electrode. Wafer processing method.

2. The dividing step further includes a preliminary dividing step of, after dividing the outer peripheral annular portion and the central region, irradiating the outer peripheral annular portion with the laser beam to form a plurality of modified layers in a thickness direction of the first wafer, and dividing the outer peripheral annular portion into a plurality of arc-shaped portions; In the preliminary cutting step, a position of at least one of the modified layers formed in the thickness direction is a position in the thickness direction between the one end and the other end of the through electrode. The wafer processing method according to claim 1 .

3. The dividing step further includes an interface processing step of irradiating a laser beam having a wavelength that is transparent to the first wafer or the second wafer along an interface where the first wafer and the second wafer are bonded together in the outer peripheral annular portion, to form a modified layer that serves as a peeling starting point at the interface.

3. The wafer processing method according to claim 1 or 2.

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