Wafer processing apparatus and wafer processing method

Abstract

The present invention provides a wafer processing apparatus that positions the focal point of a laser beam on the inner side adjacent to the chamfered portion of the first wafer and irradiates it to form a modified layer, thereby facilitating the removal of the chamfered portion. [Solution] A laser processing apparatus 1 for a bonded wafer W formed by joining a first wafer 10A and a second wafer 10B, comprising: a holding table 44 for holding the second wafer of the bonded wafer; a laser beam irradiation means 8 for positioning the focal point of a laser beam on the inside adjacent to the chamfered portion formed on the outer circumference of the first wafer of the bonded wafer held on the holding table and irradiating it to form a ring-shaped modified layer; and a fluid supply means 6 for supplying a fluid that weakens the bonding force to the interface of the chamfered portion where the first wafer and the second wafer are joined. The fluid supply means includes a liquid reservoir 61 into which the chamfered portion of the bonded wafer, into which the ring-shaped modified layer is formed, allows a fluid that weakens the bonding force to penetrate to the interface of the chamfered portion.

Description

Technical Field

[0001] The present invention relates to a wafer processing apparatus and a wafer processing method for processing a bonded wafer in which a first wafer and a second wafer are bonded together.

Background Art

[0002] A wafer on which a plurality of devices such as ICs and LSIs are partitioned by a dicing line and formed on the surface is ground on the back surface to form a predetermined thickness, and then divided into individual device chips by a dicing device or a laser processing device, and is used in electric devices such as mobile phones and personal computers.

[0003] In addition, a chamfer is formed on the outer periphery of the wafer. When the back surface of the wafer is ground, the chamfer becomes a sharp knife edge, and cracks occur from the knife edge and reach the inside, damaging the device, or the operator may be injured when handling the wafer. Therefore, a technique for removing the chamfer of the wafer has been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technique of bonding a first wafer and a second wafer to improve the function of the device, and then grinding the back surface of the first wafer to form a desired thickness, there is a problem that it is relatively difficult to remove the chamfer from the first wafer.

[0006] In other words, wafers bonded by siloxane bonds or the like have strong bonding forces, and even if a laser beam with a wavelength that penetrates the wafer is focused on the inside adjacent to the chamfered area and irradiated to form a modified layer inside the first wafer, it is difficult to remove the chamfered area. Furthermore, when removing the chamfered area to be removed from the first wafer by cutting with a cutting blade, there is a problem that the second wafer may be damaged.

[0007] The present invention has been made in view of the above facts, and its main technical problem is to provide a wafer processing apparatus and wafer processing method that can solve the problem that when processing a bonded wafer formed by joining a first wafer and a second wafer, even if the focal point of a laser beam with a wavelength that is transparent to the first wafer is positioned on the inside adjacent to the chamfered portion of the first wafer and irradiated to form a modified layer, it is difficult to remove the chamfered portion. [Means for solving the problem]

[0008] To solve the above-mentioned main technical problems, the present invention provides a wafer processing apparatus for processing a bonded wafer formed by joining a first wafer and a second wafer, comprising: a holding table for holding the second wafer of the bonded wafer; a laser beam irradiation means for positioning the focal point of a laser beam on the inside adjacent to a chamfered portion formed on the outer circumference of the first wafer of the bonded wafer held on the holding table and irradiating it to form a ring-shaped modified layer; and a fluid supply means for supplying a fluid that weakens the bonding force to the interface of the chamfered portion where the first wafer and the second wafer are joined, wherein the fluid supply means includes a liquid reservoir for immersing the chamfered portion of the bonded wafer, on which the ring-shaped modified layer is formed, and introducing a fluid that weakens the bonding force to the interface of the chamfered portion.

[0009] It is preferable that a chamfering removal means is provided to remove the chamfered portion from the outer circumference of the first wafer on which the modified layer is formed. Furthermore, it is preferable that the first wafer and the second wafer are joined by Si-O-Si siloxane bonds, and the fluid that weakens the bonding force contains at least one of water or ammonia, and that the action of the fluid changes the Si-O-Si bond to a Si-OH-OH-Si bond, thereby weakening the bonding force at the interface. It is also preferable that a pressurizing means is provided to apply pressure to the fluid introduced into the liquid reservoir.

[0010] Furthermore, the present invention provides a wafer processing method for processing a bonded wafer formed by joining a first wafer and a second wafer, comprising: a preparation step of preparing the wafer processing apparatus described above; a holding step of holding the second wafer of the bonded wafer on the holding table of the wafer processing apparatus; a modified layer formation step of positioning the focal point of a laser beam on the inside adjacent to the chamfered portion formed on the outer circumference of the first wafer of the bonded wafer held on the holding table and irradiating it to form a ring-shaped modified layer; and a fluid supply step of immersing the chamfered portion of the bonded wafer on which the ring-shaped modified layer has been formed using a fluid supply means of the wafer processing apparatus and introducing a fluid that weakens the bonding force at the interface of the chamfered portion, wherein the fluid supply step involves immersing the chamfered portion of the bonded wafer on which the ring-shaped modified layer has been formed in a liquid reservoir arranged to surround the holding table and supplying a fluid that weakens the bonding force at the interface of the chamfered portion.

[0011] Furthermore, the wafer processing method of the present invention preferably includes a pressurization step in which pressure is applied to the fluid after the fluid supply step. [Effects of the Invention]

[0012] The wafer processing apparatus of the present invention is a wafer processing apparatus for processing a bonded wafer formed by joining a first wafer and a second wafer, and includes a holding table for holding the second wafer of the bonded wafer, a laser beam irradiation means for positioning the focal point of a laser beam on the inside adjacent to a chamfer formed on the outer circumference of the first wafer of the bonded wafer held on the holding table and irradiating it to form a ring-shaped modified layer, and a fluid supply means for supplying a fluid that weakens the bonding force to the interface of the chamfer formed by joining the first wafer and the second wafer, wherein the fluid supply means includes a liquid reservoir for immersing the chamfer formed on the bonded wafer and allowing the fluid that weakens the bonding force to penetrate to the interface of the chamfer, thereby weakening the bonding force in the region corresponding to the chamfer at the interface of the bonded wafer, making it possible to easily remove the chamfer of the first wafer starting from the ring-shaped modified layer, and thus solving the problem of difficulty in removing the chamfer. Furthermore, there is no need to remove the chamfered portion using a cutting blade, and the problem of scratching the second wafer to which the first wafer is bonded is avoided.

[0013] Furthermore, the wafer processing method of the present invention is a wafer processing method for a bonded wafer formed by joining a first wafer and a second wafer, comprising: a preparation step of preparing the wafer processing apparatus described above; a holding step of holding the second wafer of the bonded wafer on the holding table of the wafer processing apparatus; a modified layer formation step of positioning the focal point of a laser beam on the inside adjacent to the chamfer formed on the outer circumference of the first wafer of the bonded wafer held on the holding table and irradiating it to form a ring-shaped modified layer; and the formation of the ring-shaped modified layer by a fluid supply means of the wafer processing apparatus. The bonding process includes a fluid supply step of immersing the chamfered portion of the bonded wafer and introducing a fluid that weakens the bonding force at the interface of the chamfered portion. In this fluid supply step, the chamfered portion of the bonded wafer, on which a ring-shaped modified layer has been formed, is immersed in a liquid reservoir arranged to surround a holding table, and a fluid that weakens the bonding force at the interface of the chamfered portion is supplied. As a result, the bonding force in the area corresponding to the chamfered portion at the interface of the bonded wafer is weakened, making it possible to easily remove the chamfered portion of the first wafer starting from the ring-shaped modified layer, thus resolving the problem of difficulty in removing the chamfered portion. Furthermore, there is no need to remove the chamfered portion using a cutting blade, and the problem of damaging the second wafer on which the first wafer is bonded is avoided. [Brief explanation of the drawing]

[0014] [Figure 1] This is a perspective view of a bonded wafer processed by the processing apparatus of this embodiment. [Figure 2] This is an overall perspective view of the laser processing apparatus of this embodiment. [Figure 3] (a) An enlarged perspective view of the fluid supply means installed in the laser processing apparatus shown in Figure 2, and (b) A partially enlarged cross-sectional view of the fluid supply means shown in (a). [Figure 4] (a) A perspective view showing how a ring-shaped modified layer is formed on a bonded wafer using the laser processing apparatus shown in Figure 2. (b) An enlarged cross-sectional view of a part of the embodiment shown in (a). [Figure 5] This is a plan view showing the radially modified layer formed on the first wafer. [Figure 6] (a) A perspective view showing how a bonding force reduction region is formed at the interface of the bonding wafer by the fluid supply process, and (b) An enlarged cross-sectional view of a part of the embodiment shown in (a). [Figure 7] This is a perspective view showing how the chamfered portion is removed from the outer circumference of the first wafer. [Figure 8] (a) A perspective view showing an enlarged view of the motor and chamfer removal part of the chamfer removal means attached to the laser processing apparatus shown in Figure 2; (b) A perspective view of the chamfer removal part shown in (a) viewed from diagonally below; (c) A conceptual diagram showing how the chamfer is removed by the chamfer removal means. [Figure 9] This is a perspective view showing a grinding process performed on a bonded wafer from which the chamfered portion has been removed. [Figure 10] (a) A perspective view showing a grinding process performed to remove the chamfered portion, and (b) A perspective view showing a process in which the chamfered portion of the first wafer of the bonded wafer is removed and grinding is performed. [Modes for carrying out the invention]

[0015] Hereinafter, embodiments relating to a wafer processing apparatus and a wafer processing method constructed based on the present invention will be described in detail with reference to the attached drawings.

[0016] FIG. 1 shows an example of a bonded wafer W processed by the wafer processing apparatus and the wafer processing method of the present embodiment. The illustrated bonded wafer W is a bonded wafer in which a first wafer 10A and a second wafer 10B are bonded together. The first wafer 10A is, for example, a silicon (Si) wafer having a diameter of 300 mm and a thickness of 775 μm, and a plurality of devices 12A are formed on a surface 10Aa partitioned by a dicing line 14A. The first wafer 10A has a surface 10Aa and a back surface 10Ab, and includes a central device region 16A where devices 12A used as products are formed, and an outer peripheral surplus region 18A surrounding the device region 16A where chamfer portions 17A are formed on the outer periphery.

[0017] The second wafer 10B also has the same configuration as the first wafer 10A, and chamfer portions 17B are formed on the outer periphery. Although not shown, on a surface 10Ba facing the lower surface side in the figure, a plurality of devices corresponding to the devices 12A of the first wafer 10A are partitioned by dicing lines and formed, which is a silicon wafer having a diameter of 300 mm and a thickness of 775 μm. The width in which the chamfer portions 17A and 17B are formed is, for example, 0.6 to 6 mm, and the width of the chamfer portions 17A and 17B of the bonded wafer W of the present embodiment is formed to be 5 mm.

[0018] In the present embodiment, the first wafer 10A and the second wafer 10B of the bonded wafer W are bonded together, for example, by bonding the surface 10Aa of the first wafer 10A and the surface 10Ba of the second wafer 10B to form an interface 20 by a siloxane bond. The siloxane bond is a Si-O-Si bond in which silicon (Si) and oxygen (O) are alternately bonded, and since the first wafer 10A and the second wafer 10B are bonded by heat treatment, a strong bonding state is maintained even at high temperatures.

[0019] Referring to Figure 2, a laser processing apparatus 1 configured according to the present invention and suitable for carrying out the wafer processing method of the present invention will be described. The illustrated laser processing apparatus 1 includes a holding table 44 for holding the second wafer 10B of the bonded wafer W described above, a laser beam irradiation means 8 for positioning the focal point of a laser beam on the inside adjacent to the chamfered portion 17A formed on the outer circumference of the first wafer 10A of the bonded wafer W held on the holding table 44 and irradiating it to form a ring-shaped modified layer, and a fluid supply means 6 for supplying a fluid L to weaken the bonding force to the interface 20 of the chamfered portions 17A and 17B where the first wafer 10A and the second wafer 10B are bonded.

[0020] The laser processing apparatus 1 is disposed on a base 2 and, in addition to the above configuration, includes a holding means 4 including a holding table 44 for holding the bonded wafer W, a moving means 5 for moving the holding means 4, an imaging means 7 for imaging the bonded wafer W held on the holding table 44 of the holding means 4 and performing alignment, a frame 3 consisting of a vertical wall portion 3a erected to the side of the moving means 5 and a horizontal wall portion 3b extending horizontally from the upper end of the vertical wall portion 3a, a display means M disposed on the frame 3, a chamfering portion removal means 30 for removing the chamfered portion 17A from the outer circumference of the first wafer 10A on which the modified layer is formed, and a control means (not shown).

[0021] As can be seen from Figure 2, the holding means 4 comprises a rectangular X-axis movable plate 41 mounted on a base 2 so as to be movable in the X-axis direction, a rectangular Y-axis movable plate 42 disposed on the X-axis movable plate 41 so as to be movable in the Y-axis direction, and a substantially cylindrical support column 43 fixed to the upper surface of the Y-axis movable plate 42, with the holding table 44 disposed at the upper end of the support column 43. As can be seen from Figure 3(a), the holding table 44 is composed of a holding surface 44a formed of a breathable material and a frame 44b surrounding the holding surface 44a and connected to a suction means (not shown), and is configured to be rotatable by a rotational drive means (not shown). A liquid reservoir 61, which constitutes the fluid supply means 6, is disposed on the holding table 44, and the liquid reservoir 61 is configured to be open at the top and surround the holding table 44.

[0022] Returning to Figure 2 and continuing the explanation, the moving means 5 includes an X-axis moving means 5a that moves the holding means 4 in the X-axis direction, and a Y-axis moving means 5b that moves the holding means 4 in the Y-axis direction which is perpendicular to the X-axis direction. The X-axis moving means 5a converts the rotational motion of the motor 51 into linear motion via a ball screw 52 and transmits it to the X-axis movable plate 41, moving the X-axis movable plate 41 in the X-axis direction along a pair of guide rails 2a, 2a arranged on the base 2 along the X-axis direction. Details of the Y-axis moving means 5b are not shown, but it has a similar configuration to the X-axis moving means 5a described above, transmitting the rotational motion of the motor to the Y-axis movable plate 42, moving the Y-axis movable plate 42 along a pair of guide rails 41a, 41a arranged on the X-axis movable plate 41 along the Y-axis direction.

[0023] The optical system constituting the laser beam irradiation means 8 is housed inside the horizontal wall portion 3b of the frame 3. A light concentrator 81, which is part of the laser beam irradiation means 8, is disposed on the lower surface of the tip of the horizontal wall portion 3b, and focuses a laser beam of a wavelength that is penetrating to the first wafer 10A of the bonded wafer W and irradiates the bonded wafer W with it. Furthermore, an imaging means 7 is disposed at a position adjacent to the light concentrator 81 in the X-axis direction. The imaging means 7 is a camera that images the bonded wafer W held on the holding table 44 of the holding means 4 and detects the processing position to be irradiated with the laser beam.

[0024] As can be seen from Figures 2 and 3(a), adjacent to the liquid reservoir 61, which is arranged to surround the holding table 44, is a fluid supply pump 63 that supplies a fluid L to the storage section 6a of the liquid reservoir 61 to weaken the bonding force at the interface 20 of the chamfered sections 17A and 17B, and a supply pipe 63a that guides the fluid L discharged from the fluid supply pump 63 to the liquid reservoir 61. Also adjacent to the liquid reservoir 61 is a drain pump 64 that discharges the fluid L stored in the storage section 6a of the liquid reservoir 61 to the outside, and a drain pipe 64a that discharges the fluid L from the liquid reservoir 61 via the drain pump 64. The fluid L supplied from the fluid supply pump 63 is preferably a fluid containing at least one of water or ammonia, and may be a mixture of water and ammonia.

[0025] The fluid supply pump 63 and the drain pump 64 are arranged on the Y-axis movable plate 42 and move in the X-axis and Y-axis directions together with the support column 43 and the holding table 44 by operating the moving means 5 described above. As shown in Figures 3(a) and (b), an annular cover member 62 is provided at the bottom of the liquid reservoir tank 61, and the supply pipe 63a and the drain pipe 64a described above are connected to the bottom 61a of the liquid reservoir tank 61 via the cover member 62. The holding table 44, which constitutes the upper surface of the support column 43, is arranged to protrude upward from the center of the bottom 61a of the liquid reservoir tank 61, and an annular sealing member 6b is provided between the bottom 61a of the liquid reservoir tank 61 and the support column 43. The holding table 44 is rotatably supported by a rotational drive means (not shown) and is configured to be rotatable relative to the liquid reservoir tank 61 which is fixed to the Y-axis movable plate 42 by a fixing means (not shown). Because the sealing member 6b described above is provided, even if the holding table 44 rotates while fluid L is stored in the storage section 61a of the liquid reservoir tank 61, the fluid L is prevented from leaking out of the liquid reservoir tank 61. As shown in Figure 3(b), a suction passage 43a connected to a suction means (not shown) is formed inside the support column 43. By operating the suction means, a negative pressure Vm can be generated on the holding surface 44a of the holding table 44.

[0026] The laser processing apparatus 1 of this embodiment has a configuration that is generally as described above, and the wafer processing method of this embodiment, which will be described below, is performed by the laser processing apparatus 1. The laser processing method described below is a laser processing method that forms a ring-shaped modified layer on the inside adjacent to the chamfered portion 17A formed on the outer circumference of the first wafer 10A of the bonded wafer W described above.

[0027] In carrying out the wafer processing method of this embodiment, a preparatory step is performed to prepare a laser processing apparatus 1 which includes the above-described holding table 44, a laser beam irradiation means 8, and a fluid supply means 6 that supplies a fluid L to weaken the bonding force to the interface 20 of the chamfered portions 17A and 17B where the first wafer 10A and the second wafer 10B of the bonded wafer W held on the holding table 44 are joined. The fluid supply means 6 is equipped with a liquid reservoir 61 into which the chamfered portions 17A and 17B of the bonded wafer W, which has a ring-shaped modified layer formed thereon, are immersed and the fluid L to weaken the bonding force is introduced into the interface 20 of the chamfered portions 17A and 17B.

[0028] Once the laser processing apparatus 1 described above is prepared, the bonded wafer W described above is transported to the laser processing apparatus 1 by a transport means (not shown) and a holding process is performed in which the second wafer 10B of the bonded wafer W is held on the holding table 44. In this holding process, the second wafer 10B of the bonded wafer W transported to the laser processing apparatus 1 is placed on the holding table 44 with the back surface 10Ab of the first wafer 10A facing upwards, and a suction means (not shown) is activated to hold the bonded wafer W on the holding table 44 by suction. Although not shown, protective tape may be attached to the back surface 10Bb side of the second wafer 10B, which is positioned downwards when placed on the holding table 44. By applying the protective tape, even when the bonded wafer W is immersed in the liquid reservoir 61 with the fluid L stored therein, as described later, the fluid L is prevented from being sucked out from the holding surface 44a of the holding table 44.

[0029] Next, if necessary, alignment is performed using the imaging means 7 installed in the laser processing apparatus 1. The bonded wafer W is imaged by this alignment, and the position of the outer edge where the chamfered portion 17A of the first wafer 10A is formed and the height of the upper surface of the back surface 10Ab of the first wafer 10A are detected. The processing position to be irradiated by positioning the focal point of the laser beam LB in the region corresponding to the inner outer peripheral excess region 18A adjacent to the chamfered portion 17A formed on the outer periphery of the first wafer 10A is detected. In this embodiment, the diameter of the bonded wafer W is 300 mm, and the processing position is detected as a radius of 145 mm from the center point of the first wafer 10A.

[0030] Once the alignment is performed as described above, the laser beam irradiation means 8 described above is used to position the focal point of the laser beam at the processing position detected by the alignment and irradiate it to perform a modified layer formation process to form a ring-shaped modified layer.

[0031] More specifically, based on the positional information of the processing position detected by the alignment described above, the moving means 5 described above is activated to move the holding table 44, and as shown in Figure 4(a), the processing position set on the outer circumference of the first wafer 10A of the bonded wafer W is positioned directly below the concentrator 81 of the laser beam irradiation means 8. Next, as can be understood from Figure 4(b) in addition to Figure 4(a), the laser beam irradiation means 8 is activated to position the focal point of a laser beam LB with a wavelength that is transparent to the first wafer 10A inside the processing position on the first wafer 10A from the back surface 10Ab side of the first wafer 10A and irradiate it, and the holding table 44 is rotated in the direction indicated by arrow R1 in Figure 4(a) to form a ring-shaped modified layer 100 all around along the inside of the chamfered portion 17A of the first wafer 10A.

[0032] In this embodiment, it is preferable to form the modified layer 100 in multiple layers in the vertical direction. For example, in the modified layer 100 shown in Figure 4(b), the focal point of the laser beam LB is positioned at a location set so that the modified layer is formed at a depth of 650 μm from the back surface 10Ab near the interface 20, inside the inner part adjacent to the chamfered portion 17A of the first wafer 10A, and the holding table 44 is rotated to form the first ring-shaped modified layer along the chamfered portion 17A. Subsequently, while rotating the chuck table 34, the depth of the focal point from the back surface 10Ab is raised three times from 500 μm → 350 μm → 200 μm, thereby forming a total of four ring-shaped modified layers (not shown) in the vertical direction along the chamfered portion 17A. The modified layer 100 formed by the laser beam irradiation means 8 is not limited to being formed in four layers as described above, but is appropriately set depending on the thickness of the first wafer 10A, the material constituting the first wafer 10A, the wavelength and output of the laser beam LB irradiated by the laser beam irradiation means 8, etc. This completes the wafer processing method of this embodiment.

[0033] The laser processing conditions for forming the modified layer 100 are set, for example, as follows. Wavelength: 1099 nm or 1342 nm Repeat frequency: 80kHz Average output: 2.0W Holding table rotation speed: 60 rpm

[0034] In the modified layer formation process described above, in addition to the modified layer 100, a radial modified layer 110 may be formed extending from the region where the modified layer 100 is formed toward the outer peripheral edge where the chamfered portion 17A is formed, for example, as shown in Figure 5. The illustrated modified layer 110 is formed, for example, by irradiating a laser beam LB under the same laser processing conditions as when forming the modified layer 100 described above, and is formed at multiple locations (four locations in the illustrated embodiment) at equal intervals on the outer periphery of the first wafer 10A. By forming this modified layer 110, when the chamfered portion 17A is removed from the first wafer 10A, the chamfered portion 17A is more finely divided, and the removal of the chamfered portion 17A is achieved more effectively.

[0035] As described above, after forming the ring-shaped modified layer 100 on the outer circumference of the first wafer 10A, a fluid supply process is carried out by the fluid supply means 6 described above, in which the chamfered portions 17A and 17B of the bonded wafer W on which the modified layer 100 is formed are immersed and a fluid L that weakens the bonding force is introduced into the interface 20 of the chamfered portions 17A and 17B. More specifically, the fluid supply pump 63 of the fluid supply means 6 described above is operated to supply a predetermined amount of fluid L to the storage portion 6a of the liquid reservoir tank 61 via the supply pipe 63a, as shown in Figure 6(a). At this time, the drain pump 64 is stopped and the fluid L is not drained from the drain pipe 64a. The predetermined amount of fluid L is the amount to which the chamfered portions 17A and 17B of the bonded wafer W held on the holding table 44 are immersed and a sufficient amount of fluid L that weakens the bonding force is supplied to the interface 20 of the bonded wafer W, as shown in Figure 6(b).

[0036] The interface 20 in this embodiment is joined by siloxane bonds (Si-O-Si bonds), and when the above-mentioned fluid L is supplied to the interface 20 from the side, water molecules gradually penetrate the interface 20, and the penetrated area changes to Si-OH-OH-Si bonds. By performing this fluid supply process, the bonding force of the interface 20 is weakened, and as shown in Figure 6(b), an annular bonding force reduction region 22 is formed on the outer circumference of the interface 20 of the bonded wafer W, from the outer edges of the chamfered portions 17A and 17B, in the region where the modified layer 100 is formed, where the bonding force is weaker than that of the siloxane bonds. Once the bonding force reduction region 22 has been formed as described above, the above-mentioned drainage pump 64 is operated to drain the fluid L from the liquid reservoir tank 61. With this, the wafer processing method of this embodiment is completed.

[0037] Although not shown in the figures, the above-described embodiment may also include a pressurizing means for applying pressure to the fluid L introduced into the liquid reservoir 61. This pressurizing means can be configured, for example, by providing a lid member that closes the top of the liquid reservoir 61 to make the storage section 6a airtight, and by providing an air pump that introduces compressed air into the space formed between the fluid L and the lid member when the fluid L is stored in the liquid reservoir 61. By providing such a pressurizing means, after performing the above-described fluid supply step and supplying a predetermined amount of fluid L to the storage section 6a, the pressurizing means can be activated to perform a pressurizing step that applies pressure to the fluid L in the liquid reservoir 61. By performing this pressurizing step, the fluid L is promoted to enter the interface 20 of the chamfered portions 17A and 17B of the bonded wafer W, and an annular bond strength reduction region 22, which has a weaker bond strength compared to the siloxane bond, is formed more efficiently at the interface 20 of the bonded wafer W. The pressurizing means is not limited to the pressurizing means described above. For example, it may be implemented by a nozzle that pressurizes fluid L from the side and applies a water flow to the interface 20 of the chamfered portions 17A and 17B of the bonded wafer W within the liquid reservoir 61. When such a nozzle is installed, it is not necessary for the liquid reservoir 61 to be a sealed structure. However, when the fluid L is ejected from the nozzle onto the bonded wafer W, it is preferable to rotate the holding table 44 using the rotary drive means described above to eject the fluid L around its entire circumference.

[0038] If the above wafer processing method is carried out using the laser processing apparatus 1 described above, and a modified layer 100 is formed on the outer circumference of the first wafer 10A and a bonding force reduction region 22 is formed on the outer circumference of the interface 20 of the bonded wafer W, then a chamfer removal step can be carried out to remove the chamfered portion 17A, including the outer circumference excess region 18A, from the outer circumference of the first wafer 10A, as shown in Figure 7. In the bonded wafer W, since the modified layer 100 described above is formed on the first wafer 10A and the bonding force reduction region 22 is formed, the chamfered portion 17A can be easily removed from the first wafer 10A by applying a simple external force. The laser processing apparatus 1 of this embodiment is equipped with a chamfered portion removal means 30 as shown in Figures 2 and 8, and the chamfered portion 17A can be removed by the chamfered portion removal means 30.

[0039] As shown in Figure 2, the chamfer removal means 30 includes a casing 32 extending upward from the ends of the guide rails 2a, 2a on the base 2, and an arm 34 that is supported by the casing 32 so as to be able to move up and down and extends in the X-axis direction. The casing 32 has a built-in lifting mechanism (not shown) for raising and lowering the arm 34. A motor 36 is disposed at the tip of the arm 34, and a chamfer removal part 38 is connected to the lower surface of the motor 36, which is rotationally driven by the motor 36 about an axis that extends in the vertical direction.

[0040] Figure 8(a) shows an enlarged view of the motor 36 and chamfered portion removal section 38 of the chamfered portion removal means 30 described above, and Figure 8(b) shows the chamfered portion removal section 38 shown in Figure 8(a) viewed from diagonally below. As can be seen from Figure 8(b), the chamfered portion removal section 38 is configured in a ring shape, and a plurality of blades 384 for removing the chamfered portion 17A of the first wafer 10A described above are arranged on the inner surface of the ring-shaped chamfered portion removal section 38. These blades 384 are thin, razor-like blades, and as the chamfered portion removal section 38 is driven by the motor 36 and rotates forward and backward in the direction indicated by arrow R2 in the figure, they protrude inward as indicated by arrow R3 in the figure, or are housed inside the chamfered portion removal section 38.

[0041] As described above, after forming the modified layer 100 on the outer peripheral excess region 18A of the first wafer 10A, the X-axis moving means 5a and Y-axis moving means 5b are operated to position the holding table 44 holding the bonded wafer W below the chamfered portion removal unit 38 in order to remove the chamfered portion 17A. Next, the arm 34 is lowered so that the lower surface 382 of the chamfered portion removal unit 38 shown in Figure 8(b) is brought into close contact with the back surface 10Ab of the first wafer 10A of the bonded wafer W. Then, the motor 36 of the chamfered portion removal means 30 operates the chamfered portion removal unit 38 so that the blade 384 protrudes inward as shown by arrow R3 in Figure 8(c). This allows the blade 384 to enter the bonding force reduction region 22 formed at the interface 20 of the bonded wafer W, and the holding table 44 to rotate, thereby fracturing the outer peripheral excess region 18A, including the chamfered portion 17A, starting from the modified layer 100.

[0042] As described above, after the chamfered portion 17A is broken off from the first wafer 10A, the motor 36 is operated to house the blade 384 inside the chamfered portion removal section 38, and the arm 34 of the chamfered portion removal means 30 is raised, so that the chamfered portion 17A is removed from the first wafer 10A of the bonded wafer W. Once the chamfered portion 17A has been removed from the first wafer 10A of the bonded wafer W in this way, a grinding process is performed to grind the back surface 10Ab of the first wafer 10A to form the desired thickness, if necessary.

[0043] When performing the grinding process, the bonded wafer W from which the chamfered portion 17A has been removed is transported to the grinding apparatus 70 (partially shown) shown in Figure 9. As shown in the figure, the grinding apparatus 70 is equipped with a grinding means 72 for grinding and thinning the bonded wafer W which is held by suction on the chuck table 71. The grinding means 72 includes a rotating spindle 72a which is rotated by a rotational drive mechanism (not shown), a wheel mount 72b attached to the lower end of the rotating spindle 72a, and a grinding wheel 72c attached to the lower surface of the wheel mount 72b, and a plurality of grinding wheels 72d are arranged in an annular shape on the lower surface of the grinding wheel 72c.

[0044] Once the bonded wafer W is transported to the grinding apparatus 70, as shown in Figure 9, it is placed on the chuck table 71 with the second wafer 10B side facing downwards, and a suction means (not shown) is activated to hold it in place. Next, the rotating spindle 72a of the grinding means 72 is rotated at, for example, 6000 rpm in the direction indicated by arrow R4 in Figure 9, while the chuck table 71 is rotated at, for example, 300 rpm in the direction indicated by arrow R5. Then, grinding water is supplied onto the back surface 10Ab of the first wafer 10A by a grinding water supply means (not shown), and a grinding feed means (not shown) is activated to bring the grinding wheel 72d into contact with the back surface 10Ab of the first wafer 10A, and the grinding wheel 72c is fed downwards at, for example, a grinding feed speed of 1.0 μm / second, in the direction indicated by arrow R6. In this process, the thickness of the bonded wafer W can be measured using a contact-type or non-contact-type measuring gauge (not shown) while grinding is performed, allowing the wafer to be thinned until the desired thickness is reached.

[0045] Once the back surface 10Ab of the first wafer 10A has been ground by a predetermined amount to form the bonded wafer W to the desired thickness, the grinding means 72 is stopped and retracted upward to complete the grinding process. After the grinding process is completed, cleaning, drying, and other treatments are carried out as appropriate, although the details are omitted.

[0046] According to the laser processing apparatus 1 and wafer processing method of the above-described embodiment, a ring-shaped modified layer 100 is formed by the modified layer formation process, and a bonding force reduction region 22 is formed on the outer circumference of the interface 20 of the bonded wafer W joined by siloxane bonds, thereby reducing the bonding force. The chamfered portion 17A of the first wafer 10A can be easily removed starting from the ring-shaped modified layer 100, thus resolving the problem of difficulty in removing the chamfered portion 17A. Furthermore, there is no need to remove the chamfered portion 17A using a cutting blade, and the problem of damaging the second wafer 10B to which the first wafer 10A is joined is avoided.

[0047] The present invention is not limited to the embodiments described above. Although the laser processing apparatus 1 in the embodiments described above is equipped with a chamfer removal means 30, the laser processing apparatus 1 does not necessarily have to be equipped with the chamfer removal means 30. If the chamfer removal means 30 is not provided, for example, it is possible to perform a chamfer removal process to remove the chamfer 17A by applying external force to the bonded wafer W by grinding the back surface 10Ab of the first wafer 10 of the bonded wafer W. More specifically, after forming the modified layer 100 described above on the first wafer 10A of the bonded wafer W, the bonded wafer W is transported to the grinding apparatus 70 as shown in Figure 10(a), and placed on the chuck table 71 with the second wafer 10B side facing downwards and the back surface 10Ab of the first wafer 10A facing upwards, and held by suction.

[0048] Next, the rotating spindle 72a of the grinding means 72 is rotated at, for example, 6000 rpm in the direction indicated by arrow R4 in Figure 10(a), while the chuck table 71 is rotated at, for example, 300 rpm in the direction indicated by arrow R5. Then, grinding water is supplied onto the back surface 10Ab of the first wafer 10A by a grinding water supply means (not shown), and a grinding feed means (not shown) is activated to bring the grinding wheel 72d into contact with the back surface 10Ab of the first wafer 10A, and the grinding wheel 72c is fed downwards at, for example, a grinding feed rate of 1.0 μm / second, indicated by arrow R6. As a result, an external force is applied to the back surface 10Ab of the first wafer 10A, and the excess outer peripheral region 18A including the chamfered portion 17A is removed, with the modified layer 100 as the starting point for separation. In this case, it is preferable that a radially shaped modified layer 110 is formed as described above, and the chamfered portion 17A is appropriately divided on the outer circumference starting from the radially shaped modified layer 110 and removed well from the first wafer 10A. When grinding the back surface 10Ab of the first wafer 10A of the bonded wafer W with the grinding device 70, rough grinding is first performed with a grinding wheel suitable for rough grinding, and the chamfered portion 17A is removed starting from the modified layers 100 and 110, and rough grinding is performed until a predetermined thickness is reached, and then finish grinding of the back surface 10Ab of the first wafer 10A is performed with a grinding wheel suitable for finish grinding.

[0049] As described above, once the back surface 10Ab of the first wafer 10A is ground by a predetermined amount to obtain the desired thickness of the bonded wafer W, the grinding means 72 is stopped and retracted upward, completing the grinding process, and a bonded wafer W of the desired thickness with the chamfered portion 17A removed can be obtained, as shown on the left side of Figure 10(b). After the grinding process is completed, cleaning, drying, etc., are carried out as appropriate, details of which are omitted. In this way, the grinding device 70 also makes it possible to easily remove the chamfered portion 17A of the first wafer 10A starting from the ring-shaped modified layer 100, similar to the embodiment described earlier, thus resolving the problem of difficulty in removing the chamfered portion 17A. Furthermore, there is no need to remove the chamfered portion 17A using a cutting blade, and the problem of scratching the second wafer 10B to which the first wafer 10A is bonded is avoided.

[0050] Although the bonded wafer W described above was formed by joining a first wafer 10A and a second wafer 10B by siloxane bonding, the bonded wafer processed by the wafer processing apparatus and wafer processing method of the present invention is not limited to wafers joined by siloxane bonding. For example, the bonded wafer may be formed by joining the first wafer 10A and the second wafer 10B by SiCN bonding through nitride bonding, by TEOS bonding by changing tetraethyl orthosilicate molecules into a solid with Si-O-Si bonding, or by oxidizing the surface of a silicon wafer in an oxygen atmosphere to bond it by ThOx bonding through a silicon oxide film (SiO2). In any case, the bonding force can be weakened by the fluid L described above. Furthermore, the wafer processing apparatus and wafer processing method of the present invention can also be applied to bonded wafers W that have been bonded by applying O2 plasma treatment or N2 plasma treatment as a pretreatment to the bonding surface forming the interface 20. [Explanation of Symbols]

[0051] 1: Laser processing equipment 2: Base 3:Frame body 4: Holding means 41:X-axis movable plate 42: Y-axis movable plate 43: Strut 44: Holding Table 44a: Holding surface 44b:Frame body 5: Means of transportation 5a:X-axis movement means 5b: Y-axis movement means 6:Fluid supply means 61: Liquid reservoir 62: Cover component 63: Fluid supply pump 64: Drainage pump 7: Imaging means 8: Laser beam irradiation means 81: Light concentrator 10A: First wafer 10Aa: Surface 10Ab: Reverse side 12A: Device 14A: Planned division line 16A: Device area 17A: Chamfered section 18A: Outer perimeter surplus area 10B: Second wafer 17B: Chamfered section 20: Interface 22: Bonding force reduction area 30: Means for removing chamfered portion 32: Casing 34: Arm 36: Motor 38: Chamfered part removal part 382: Bottom surface 384: Blade 70: Grinding equipment 71: Chuck Table 72: Grinding methods 72d: Grinding wheel

Claims

1. A wafer processing apparatus for processing a bonded wafer formed by joining a first wafer and a second wafer, A holding table for holding the second wafer of the bonded wafer, A laser beam irradiation means that positions the focal point of a laser beam on the inner side adjacent to the chamfer formed on the outer circumference of the first wafer of the bonded wafer held on the holding table, and irradiates it to form a ring-shaped modified layer, The system includes a fluid supply means for supplying a fluid that weakens the bonding force at the interface of the chamfered portion where the first wafer and the second wafer are joined, The fluid supply means is a wafer processing apparatus that includes a liquid reservoir for immersing the chamfered portion of a bonded wafer, on which a ring-shaped modified layer is formed, and introducing a fluid that weakens the bonding force at the interface of the chamfered portion.

2. A wafer processing apparatus according to claim 1, wherein a chamfer removal means is provided for removing a chamfered portion from the outer circumference of a first wafer on which a modified layer has been formed.

3. The first wafer and the second wafer are joined by a Si-O-Si siloxane bond. The fluid that weakens the bonding force includes at least one of water or ammonia. The wafer processing apparatus according to claim 1, wherein the action of the fluid changes the Si-O-Si bond to a Si-OH-OH-Si bond, thereby weakening the bonding force at the interface.

4. The wafer processing apparatus according to claim 1, further comprising pressurizing means for applying pressure to the fluid introduced into the liquid reservoir tank.

5. A wafer processing method comprising processing a bonded wafer formed by joining a first wafer and a second wafer, A preparation step for preparing a wafer processing apparatus as described in any one of claims 1 to 4, A holding step in which the second wafer of the bonded wafer is held on the holding table of the wafer processing equipment, A modified layer formation step involves positioning the focal point of a laser beam on the inner side adjacent to the chamfered portion formed on the outer circumference of the first wafer of the bonded wafer held on the holding table, and irradiating it to form a ring-shaped modified layer. The process includes a fluid supply step in which a fluid that weakens the bonding force is introduced into the interface of the chamfered portion of a bonded wafer, which has a ring-shaped modified layer formed on it, by a fluid supply means of a wafer processing apparatus, The fluid supply step is a wafer processing method comprising immersing the chamfered portion of a bonded wafer, on which a ring-shaped modified layer has been formed, in a liquid reservoir arranged to surround a holding table, and supplying a fluid that weakens the bonding force to the interface of the chamfered portion.

6. The wafer processing method according to claim 5, further comprising a pressurization step of applying pressure to the fluid after the fluid supply step.

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