Wafer processing apparatus and wafer processing method

Abstract

The present invention provides a wafer processing apparatus and a wafer processing method that can appropriately remove the chamfered portion of the first wafer when processing a bonded wafer obtained by joining a first wafer and a second wafer. [Solution] A wafer processing apparatus 1 for processing a bonded wafer W formed by joining a first wafer 10A and a second wafer 10B, comprising: a rotatable holding table 44 equipped with a holding surface 441 for suction holding the second wafer 10B of the bonded wafer W; a laser beam irradiation means 8 that positions the focal point of a laser beam on the inside adjacent to the chamfered portion formed on the outer circumference of the first wafer 10A of the bonded wafer W held on the holding table 44 and irradiates it to form a ring-shaped modified layer; a liquid supply means 20 that supplies a liquid to weaken the bonding force at the interface of the chamfered portion where the first wafer 10A and the second wafer 10B are joined; and a liquid removal means that removes the liquid supplied by the liquid supply means 20 that has spread to the back surface of the second wafer 10B.

Description

Technical Field

[0001] The present invention relates to a wafer processing apparatus and a wafer processing method.

Background Art

[0002] Wafers having a plurality of devices such as ICs and LSIs partitioned by scheduled division lines and formed on the surface are ground on the back side to a predetermined thickness, then divided into individual device chips by a dicing apparatus or a laser processing apparatus, and used in electrical equipment such as mobile phones, personal computers, and electrical components.

[0003] In addition, a chamfered portion is formed on the outer periphery of the wafer. When the back side of the wafer is ground, the chamfered portion becomes a sharp knife edge, from which cracks originate and propagate inward, causing problems such as damaging the devices formed in the region near the center, or injuring the operator by the chamfered portion that has become a knife edge. Accordingly, techniques for removing the chamfered portion of the wafer have been proposed (for example, refer to Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problem to be Solved by the Invention

[0005] However, in the technique of forming a bonded wafer by bonding a first wafer and a second wafer to improve device functions, and then grinding the back side of the first wafer, there is a problem that it is relatively difficult to remove the chamfered portion from the first wafer.

[0006] In particular, wafers bonded by siloxane bonds (Si-O-Si bonds) have strong bonding forces, and even if a laser beam with a wavelength that is transparent to the first wafer is focused and irradiated on the inside adjacent to the chamfered area to form a modified layer inside the first wafer, it is difficult to remove the chamfered area effectively by this method alone. Furthermore, it is conceivable to remove the chamfered area by cutting it with a cutting blade, but this risks damaging the other bonded wafer (the second wafer).

[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 a wafer processing method that can appropriately remove the chamfered portion of the first wafer when processing a bonded wafer obtained by joining a first wafer and a second wafer. [Means for solving the problem]

[0008] To solve the main technical problems described above, 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 rotatable holding table equipped with a holding surface for suction holding the second wafer of the bonded wafer; a laser beam irradiation means that positions 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 irradiates it to form a ring-shaped modified layer; a liquid supply means that supplies a liquid to weaken the bonding force at the interface of the chamfer formed by joining the first wafer and the second wafer; and a liquid removal means that removes the liquid supplied by the liquid supply means that has spread to the back surface of the second wafer.

[0009] The liquid removal means may be a means n that sets the holding surface of the holding table to be slightly larger than the second wafer and removes the liquid that has seeped around to the back surface of the second wafer by sucking it from the outer circumference of the holding surface. Alternatively, the liquid removal means may be a means that sets the holding surface of the holding table to be smaller than the second wafer and removes the liquid that has seeped around to the back surface of the second wafer that overhangs from the holding table by sucking it. Furthermore, the liquid removal means may be a means that sets the holding surface of the holding table to be smaller than the second wafer and removes the liquid that has seeped around to the back surface of the second wafer that overhangs from the holding table by blowing it away with air.

[0010] The liquid supply means preferably includes a liquid supply nozzle having a tip for ejecting the liquid, a planar moving means for positioning the liquid supply nozzle by moving it closer to and away from the interface of the chamfered portion in the planar direction of the bonded wafer, and a thickness-direction moving means for positioning the tip of the liquid supply nozzle by moving it in the thickness direction of the bonded wafer relative to the interface of the chamfered portion.

[0011] Preferably, the tip of the liquid supply nozzle is shaped like a hypodermic needle, the amount of liquid supplied from the tip of the liquid supply nozzle is adjusted so that it does not fall due to surface tension, and the position of the tip of the liquid supply nozzle in the planar and thickness directions is adjusted so that the liquid supplied from the tip of the liquid supply nozzle is absorbed by capillary action at the interface of the chamfered portion of the bonded wafer.

[0012] The holding table rotates at a speed at which the liquid supplied from the tip of the liquid supply nozzle is absorbed by capillary action against centrifugal force, and the liquid removal means may remove the liquid from the back surface of the second wafer by the centrifugal force. The processing apparatus may also be provided with a chamfering removal means for removing the chamfered portion from the outer circumference of the first wafer on which the modified layer is formed. The holding table may also be provided with a centering means for aligning the center of the bonded wafer held on the holding table with the center of the holding table. The first wafer and the second wafer are joined by a Si-O-Si siloxane bond, and the liquid that weakens the bonding force preferably contains either water or ammonia and is supplied from the liquid supply means, and the Si-O-Si bond is changed to a Si-OH-OH-Si bond, thereby weakening the bonding force.

[0013] According to the present invention, a wafer processing method is provided for processing a bonded wafer in which a first wafer and a second wafer are joined using the wafer processing apparatus described above, comprising: a holding step of holding the second wafer of the bonded wafer by suction using a holding table; a liquid supply step of supplying a liquid that weakens the bonding force to the interface of the chamfered portion where the first wafer and the second wafer are joined; a liquid removal step of removing the liquid supplied in the liquid supply step that has seeped to the back surface of the second wafer; 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 chamfered portion removal step of applying an external force to the first wafer to remove the chamfered portion. [Effects of the Invention]

[0014] 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, comprising: a rotatable holding table equipped with a holding surface for suction holding of the second wafer of the bonded wafer; a laser beam irradiation means that positions 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 irradiates it to form a ring-shaped modified layer; a liquid supply means that supplies a liquid to weaken the bonding force at the interface of the chamfered portion where the first wafer and the second wafer are joined; and by the liquid supply means Since the system includes a liquid removal means for removing liquid supplied and that has seeped around to the back surface of the second wafer, when processing a bonded wafer formed by joining a first wafer and a second wafer, the chamfered portion can be easily removed starting from the ring-shaped modified layer that weakens the bonding force on the outer periphery of the interface between the first wafer and the second wafer. This solves the problem of difficulty in removing the chamfered portion of the first wafer, and also eliminates the problem of contamination of the transport path by properly removing the liquid supplied when forming a bonding force reduction region at the interface. [Brief explanation of the drawing]

[0015] [Figure 1] A perspective view of the bonded wafer, which is the workpiece. [Figure 2] An overall perspective view of the processing apparatus of this embodiment. [Figure 3] Perspective view of the centering mechanism. [Figure 4] (a) Perspective view of the liquid supply means, (b) Front view showing the opening at the tip of the liquid supply nozzle shown in (a). [Figure 5] (a) Enlarged perspective view of the main part of the chamfer removal mechanism, (b) View of the enlarged perspective view of the main part shown in (a) from a diagonal downward angle. [Figure 6] (a) A perspective view showing an embodiment of the liquid supply process, and (b) A side view showing an enlarged view of the main part of the embodiment shown in (a). [Figure 7] (a) Perspective view of a modified example 1 of the liquid removal means, (b) Perspective view showing an embodiment of the liquid removal process. [Figure 8](a) A perspective view of Modification Example 2 of the liquid removing means, (b) A perspective view showing an embodiment of the liquid removing step by Modification Example 2 shown in (a). [Figure 9] (a) A perspective view of Modification Example 3 of the liquid removing means, (b) A perspective view showing an embodiment of the liquid removing step by Modification Example 3 shown in (a). [Figure 10] A conceptual diagram showing an enlarged part of an embodiment of the modified layer forming step. [Figure 11] A conceptual diagram showing a part of an embodiment of the chamfered portion removing step. [Figure 12] (a) A perspective view showing another embodiment of the chamfered portion removing step, (b) A perspective view showing a state in which the chamfered portion is removed by the embodiment shown in (a). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] Hereinafter, embodiments relating to a wafer processing apparatus and a wafer processing method configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0017] FIG. 1 shows an example of a bonded wafer W processed by the wafer processing apparatus and wafer processing method of the present embodiment. The bonded wafer W is a wafer formed by bonding a first wafer 10A and a second wafer 10B into an integral body as illustrated. The first wafer 10A is, for example, a silicon (Si) wafer with a diameter of 200 mm and a thickness of 700 μm, and a plurality of devices 12A are partitioned by planned division lines 14A and formed on the surface 10Aa. The first wafer 10A has a front surface 10Aa and a back surface 10Ab, and includes an effective region 16A near the center where the device 12A used as a product is formed, and an outer peripheral surplus region 18A surrounding the effective region 16A where a chamfered portion 17A is formed on the outer periphery.

[0018] In Figure 1, the second wafer 10B, whose back surface 10Bb is visible, has the same configuration as the first wafer 10A. A chamfered portion 17B is formed on its outer circumference, and on the front surface 10Ba facing downwards in the figure, multiple devices corresponding to the device 12A of the first wafer 10A are formed and partitioned by planned division lines. The second wafer 10B is also a silicon wafer with a diameter of 200 mm and a thickness of 700 μm.

[0019] In this embodiment, the first wafer 10A and the second wafer 10B of the bonded wafer W are joined together by bonding, for example, the surface 10Aa of the first wafer 10A and the surface 10Ba of the second wafer 10B, forming an interface 19 by siloxane bonding. Siloxane bonding 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 joined by heat treatment, a strong bond state is maintained even at high temperatures.

[0020] Figure 2 shows the wafer processing apparatus 1 of this embodiment. The illustrated processing apparatus 1 positions the focal point of a laser beam inward adjacent to the chamfered portion 17A formed on the outer circumference of the first wafer 10A of the bonded wafer W, and irradiates it to form a ring-shaped modified layer, and supplies a liquid that weakens the bonding force to the interface 19 near the chamfered portion 17A and the chamfered portion 17B where the first wafer 10A and the second wafer 10B are bonded. The processing apparatus 1 of this embodiment will be described in more detail below.

[0021] The processing apparatus 1 shown in Figure 2 comprises at least a rotatable holding table 44 including a holding surface 441 for suction-holding the second wafer 10B of the bonded wafer W described above; a laser beam irradiation means 8 that positions the focal point of a laser beam in the interior 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 irradiates it to form a ring-shaped modified layer; a liquid supply means 20 that supplies a liquid to weaken the bonding force to the interface 19 of the chamfered portions 17A and 17B where the first wafer 10A and the second wafer 10B are bonded; and a liquid removal means (to be described later) that removes the liquid supplied by the liquid supply means 20 that has spread to the back surface 10Bb of the second wafer 10B.

[0022] The processing apparatus 1 is disposed on a base 2 and includes a holding means 4 including a holding table 44, 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 on the side of the moving means 5 on the base 2 and a horizontal wall portion 3b extending horizontally from the upper end of the vertical wall portion 3a, 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, a display means M, and a control means (not shown).

[0023] As shown in Figure 2, the holding means 4 comprises a rectangular X-axis movable plate 41 mounted on the base 2 so as to be movable in the X-axis direction, and 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, on which the liquid supply means 20 is disposed together with the holding table 44. The chamfer removal means 30 described above is a means that is provided as needed and may be carried out by other means.

[0024] As shown in Figure 3, the holding table 44 is composed of a holding surface 441 formed from a porous material that allows for airflow, and a frame 442 surrounding the holding surface 441. The holding surface 441 is connected to a suction means (not shown) by a flow path through a rotating shaft 44a. By operating the suction means, negative pressure is generated on the upper surface of the holding surface 441, allowing the bonded wafer W to be held by suction on the holding table 44. The holding table 44 is rotated at an arbitrary rotational speed by an electric motor 44b (see Figure 4(a)). This electric motor 44b also functions as a liquid removal means according to the present invention, as will be described later. In the illustrated embodiment, the diameter of the holding table 44 is set to be smaller than the diameter of the bonded wafer W described above. When the bonded wafer W is placed on the holding table 44 and held by suction, the outer circumference of the bonded wafer W extends outward from the holding table 44, and the outer circumference is held in a state of so-called overhang. Note that the present invention is not limited to setting the diameter of the holding table 44 to be smaller than the diameter of the bonded wafer W. For example, as shown in Modification 1 described later, the diameter of the holding surface 411 of the holding table 44 may be set to be slightly larger than the diameter of the bonded wafer W.

[0025] As shown in Figures 2 and 3, the processing apparatus 1 of this embodiment is equipped with a centering means 43. The centering means 43 is a means for moving the bonded wafer W placed on the holding table 44 toward the center of the holding table 44 to align the rotation center of the holding table 44 with the center of the first wafer 10A that constitutes the bonded wafer W. As shown in Figure 3, the centering means 43 of this embodiment is equipped with a cylindrical member 431 surrounding the holding table 44, and the cylindrical member 431 is equipped with three centering mechanisms 45 at 120° intervals so as to sandwich the bonded wafer W placed on the holding table 44 from three sides. The centering mechanisms 45 are operated by a drive mechanism (not shown), and the drive mechanism is housed in a drive mechanism housing portion 43a formed on the outer circumference of the cylindrical member 431.

[0026] The illustrated center positioning mechanism 45 includes a lifting rod 451 that is configured to move up and down in the vertical direction (Z-axis direction) indicated by arrow R1 by the drive mechanism described above and to be rotatable, and a claw 452 that is horizontally disposed at the upper end of the lifting rod 451. The claw 452 rotates in the direction indicated by arrow R2, and the tips 452a of the three claws 452 contact the outer circumference of the bonding wafer W placed on the holding table 44 from three sides, so that the center of the bonding wafer W and the rotation center of the holding table 44 can be aligned.

[0027] 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 (partially not shown) 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. The Y-axis moving means converts the rotational motion of a motor (not shown) into linear motion via a ball screw 53 (shown in the figure) and transmits it 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.

[0028] 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 constitutes part of the laser beam irradiation means 8, is provided on the lower surface of the tip of the horizontal wall portion 3b, and focuses a laser beam of a wavelength that is transparent to at least the first wafer 10A described above and irradiates the bonded wafer W with it. Furthermore, an imaging means 7 is provided 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 position and orientation of the bonded wafer W, the processing position to be irradiated with the laser beam, etc.

[0029] The liquid supply means 20 of this embodiment will be described with reference to Figure 2 and Figure 4. Note that in Figure 4(a), the centering means 43 described above is omitted for the sake of explanation. The liquid supply means 20 is disposed on the Y-axis movable plate 42 and is a means for supplying a liquid that weakens the bonding force to the interface 19 of the chamfered portions 17A and 17B where the first wafer 10A and the second wafer 10B are joined. As shown in Figure 4, the liquid supply means 20 includes a liquid supply nozzle 21 for supplying liquid, a planar direction moving means 22 for moving the liquid supply nozzle 21 closer to and further away from the interface 19 formed adjacent to the chamfered portions 17A and 17B in the planar direction of the bonded wafer W (X-axis direction in this embodiment) to position it at a desired position, and a thickness direction moving means 23 for moving the liquid supply nozzle 21 in the thickness direction (Z-axis direction) of the bonded wafer W relative to the interface 19 to position it.

[0030] As shown in Figure 4(a), the liquid supply nozzle 21 comprises a nozzle body 212 including a tip 211 and a rear end 213. The nozzle body 212 is supported by a movable base 214 that moves in the thickness direction (Z-axis direction) by a thickness direction moving means 23. A liquid supply mechanism 24 is connected to the rear end 213 of the nozzle body 212. The liquid supply mechanism 24 comprises a liquid storage tank 241 and a pump 242 that sucks liquid from the liquid storage tank 241 and pumps it under pressure. The liquid storage tank 241 and the pump 242 are connected by a supply pipe 243. A three-way valve 244 is provided on the discharge side of the pump 242, and the three-way valve 244 and the liquid supply nozzle 21 are connected by a flexible tube 246. A water supply pipe 245 extending from the liquid storage tank 241 is connected to the three-way valve 244. The flow path of the liquid supplied from the liquid storage tank 241 is configured to be switchable by the three-way valve 244 between a flow path that goes through the supply pipe 243 and pump 242 to the liquid supply nozzle 21, and a flow path that goes through the water supply pipe 245 to the liquid supply nozzle 21 without going through the pump 242. Figure 4(b) shows a front view of the tip 211 of the liquid supply nozzle 21 as seen from the front. The tip 211 of the liquid supply nozzle 21 is formed with a narrow opening diameter like an injection needle, and as shown in the figure, the diameter of the opening 211a from which the liquid is supplied is preferably set in the range of 50 to 300 μm, and more preferably in the range of 80 to 120 μm. In this embodiment, the diameter of the opening 211a of the liquid supply nozzle 21 is set to 100 μm.

[0031] The liquid supplied by the liquid supply means 20 described above preferably contains either water or ammonia. It may be water alone, ammonia alone, or a mixture of water and ammonia. In addition, any liquid other than water or ammonia may be used, as long as it weakens the bonding force at the interface 19 of the bonded wafer W.

[0032] The planar moving means 22 and the thickness-direction moving means 23 are equipped with a drive mechanism, which is not shown in the figures. This drive mechanism consists of, for example, a pulse motor, a ball screw, and a guide rail. The planar moving means 22 moves the thickness-direction moving means 23, which supports the liquid supply nozzle 21, along an elongated hole 22a formed on the upper surface that extends in the X-axis direction. The thickness-direction moving means 23 also moves the movable base 214, which supports the liquid supply nozzle 21, vertically along an elongated hole 23a formed on the side surface that extends in the Z-axis direction. By operating the planar moving means 22, the liquid supply nozzle 21 can be positioned to approach and move away from the interface 19 of the chamfered portions 17A and 17B of the bonded wafer W. By operating the thickness-direction moving means 23, the tip 211 of the liquid supply nozzle 21 can be moved in the thickness direction of the bonded wafer W relative to the interface 19 of the chamfered portions 17A and 17B.

[0033] The processing apparatus 1 of this embodiment is equipped with a chamfer removal means 30 as shown in Figure 2. As shown in the figure, the chamfer removal means 30 includes a casing 32 extending upward from the ends of guide rails 2a, 2a on a 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 lifting mechanism (not shown) built in to raise and lower the arm 34. A motor 36 is installed 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.

[0034] Figure 5(a) shows an enlarged view of the motor 36 and chamfer removal section 38 of the chamfer removal means 30 described above, and Figure 5(b) shows the chamfer removal section 38 shown in Figure 5(a) viewed from diagonally below. As can be seen from Figure 5(b), the chamfer removal section 38 is configured in a ring shape, and multiple blades 384 (three in the illustrated embodiment) for removing the chamfer 17A of the first wafer 10A are arranged on the inner surface of the ring-shaped chamfer removal section 38. These blades 384 are thin, razor-like blades, and as the chamfer removal section 38 rotates forward and backward in the direction indicated by arrow R3 by the motor 36, they protrude inward or are retracted inside the chamfer removal section 38, as shown by arrow R4 in the figure.

[0035] The control means is composed of a computer and includes a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) for storing the control program and the like, a read-write random access memory (RAM) for temporarily storing detected values, calculation results, and the like, as well as an input interface and an output interface (details are not shown in the illustration). The control means is connected to the above-mentioned moving means 5, imaging means 7, laser beam irradiation means 8, planar moving means 22 and thickness direction moving means 23 of the liquid supply means 20, a pump 242, a three-way valve 244, a chamfer removal means 30, a display means M, etc., and is controlled as appropriate.

[0036] The wafer processing apparatus 1 of this embodiment has a configuration that is generally as described above, and the wafer processing method of this embodiment, which is carried out using the processing apparatus 1 described above, will be described in detail below.

[0037] (holding process) Once the bonded wafer W described in Figure 1 is prepared, the bonded wafer W is transported to the processing apparatus 1 described in Figure 2, and placed on the holding surface 441 of the holding table 44 with the first wafer 10A facing upwards and the second wafer 10B facing downwards, as shown in Figure 4(a). Although not shown, protective tape may be attached to the second wafer 10B side which is positioned downwards. At this point, before activating the suction means that generates negative pressure on the holding table 44, a centering process may be performed using the centering means 43 described in Figures 2 and 3 above to align the center of the first wafer 10A of the bonded wafer W with the rotation center of the holding table 44. In that case, the three centering mechanisms 45 described above are activated to move the claw 452 in the vertical direction indicated by the arrow R1 described above, and the height of the claw 452 is positioned at the height of the first wafer 10A. Next, the three claws 452 are rotated in the direction indicated by arrow R2 in Figure 3, and the tips 452a of each claw 452 contact the outer circumference of the first wafer 10A of the bonded wafer W from three directions, moving the bonded wafer W toward the rotation center of the holding table 44 by the tips 452a of the three claws 452. This brings the center of the first wafer 10A of the bonded wafer W to coincide with the rotation center of the holding table 44. Then, the suction means described above is activated to attract and hold the second wafer 10B of the bonded wafer W to the holding table 44. This completes the holding process. As described above, the centering means 43 can be arranged arbitrarily, and the centering process of aligning the center of the first wafer 10A of the bonded wafer W with the rotation center of the holding table 44 may be omitted.

[0038] (Liquid supply process / liquid removal process) After performing the holding process described above, the liquid supply process and liquid removal process described below are performed. When performing the liquid supply process, first, the moving means 5 described above is activated to position the bonded wafer W directly below the imaging means 7 and image the bonded wafer W. The image information of the bonded wafer W is transmitted to and stored in a control means (not shown). Based on this image information, the outer edge of the first wafer 10A of the bonded wafer W is detected. Next, the thickness direction moving means 23 of the liquid supply means 20 is activated to move the liquid supply nozzle 21 in the Z-axis direction shown in Figure 4, and as shown in Figure 6(a), the tip 211 of the liquid supply nozzle 21 is positioned at the height of the interface 19 where the first wafer 10A and the second wafer 10B are bonded. Although the thickness of the bonded wafer W is known, the imaging means 7 described above may be equipped with a height detection function to accurately detect the height position of the surface of the bonded wafer W, and the thickness direction moving means 23 described above may be activated based on this height position information. Next, based on the information of the outer peripheral edge of the first wafer 10A of the bonded wafer W detected by the imaging means 7, the planar moving means 22 is activated to position the tip 211 of the liquid supply nozzle 21 in a position close to the side of the interface 19 of the chamfered portions 17A and 17B. At this time, the distance between the tip 211 of the liquid supply nozzle 21 and the outer peripheral edge of the bonded wafer W is preferably set to a distance of 0 to 800 μm, more preferably 350 to 450 μm, and in this embodiment, it is set to 400 μm. This distance is such that, when liquid overflows from the tip 211 of the liquid supply nozzle 21, the liquid is drawn towards the interface 19 between the first wafer 10A and the second wafer 10B by capillary action. Furthermore, the center of the tip 211 opening 211a of the liquid supply nozzle 21 does not need to perfectly coincide with the height of the interface 19 where the first wafer 10A and the second wafer 10B are joined; it is sufficient if it is set within a range of ±150 μm from the height of the interface 19.

[0039] Next, as shown in Figure 6(b), a liquid L (water in this embodiment) that weakens the bonding force of the interface 19 is supplied from the tip 211 of the liquid supply nozzle 21 to the interface 19, and the holding table 44 is rotated at a predetermined rotational speed. In this embodiment, the procedure for supplying the liquid L from the liquid supply nozzle 21 to the interface 19 is as follows.

[0040] First, the pump 242 of the liquid supply means 20, as described in Figure 4(a), is activated to draw liquid L from the liquid storage tank 241 via the supply pipe 243 and pump it to the liquid supply nozzle 21 via the three-way valve 244 and flexible tube 246. As shown in Figure 6(b), once liquid L has been supplied from the tip 211 of the liquid supply nozzle 21 to the outer circumference of the bonded wafer W, the pump 242 is stopped and the three-way valve 244 is switched to connect the liquid storage tank 241 and the liquid supply nozzle 21 via the water supply pipe 245 without using the pump 242. As a result, the liquid L is drawn in by capillary action to the interface 19 side of the bonded wafer W, and because the holding table 44 is rotating at a low speed, liquid L that weakens the bonding force of the interface 19 is supplied to the interface 19 all around the outer circumference of the bonded wafer W. At this time, the amount of liquid L supplied from the liquid supply nozzle 21 to the interface 19 is set to an amount (for example, 2 ml / min) that is held at the interface 19 between the first wafer 10A and the second wafer 10B by surface tension.

[0041] As described above, the interface 19 in this embodiment is joined by siloxane bonds (Si-O-Si bonds), and when the liquid L is supplied to the interface 19 from the side, water molecules gradually penetrate the interface 19 from the outside, and the penetrated region changes to Si-OH-OH-Si bonds. As a result, the bonding force at the outer periphery of the interface 19 is weakened, and a bond strength reduction region 19a is formed in an annular shape on the outer periphery of the interface 19. In this embodiment, when supplying liquid L to the interface 19 of the bonded wafer W, the holding table 44 is set to a slow rotation speed (preferably 10 to 30 rpm, more preferably 15 rpm) such that the liquid L supplied from the tip 211 of the liquid supply nozzle 21 is absorbed by capillary action against centrifugal force.

[0042] By the way, in order to carry out the liquid supply process of this embodiment, the liquid supply means 20 described above is activated and liquid L is supplied to the interface 19 of the chamfered portions 17A and 17B of the bonded wafer W. However, some of the liquid L may flow around to the back surface 10Bb side of the second wafer 10B. Therefore, with the bonded force reduction region 19a described above formed, the electric motor 44b is activated to rotate the holding table 44 at a rotational speed V1 that is faster than the rotational speed of the holding table 44 when carrying out the liquid supply process described above, as shown in Figure 6(a). This causes the liquid L to flow outward from the back surface 10Bb of the second wafer 10B (in the direction indicated by arrow R5 in Figure 6(b)) due to centrifugal force, and the liquid L is removed from the back surface 10Bb of the second wafer 10B of the bonded wafer W. The means for rotating this holding table 44 at a rotational speed V1 is a liquid removal means that removes the liquid L supplied by the liquid supply means 20 that has flowed onto the back surface 10Bb of the second wafer 10B, thereby performing the liquid removal process. With this, the liquid supply process and the liquid removal process are completed.

[0043] In the above-described embodiment, the electric motor 44b that rotates the holding table 44 at a rotational speed (V1) functioned as a liquid removal means for performing the liquid removal process, but the present invention is not limited thereto.

[0044] (Modified example 1 of the liquid removal method) Figure 7 shows a holding table 44A that functions as a liquid removal means used in the liquid removal process of the present invention. The illustrated holding table 44A is installed in place of the holding table 44 of the holding means 4 described above. The holding table 44A has a holding surface 441A surrounded by a frame 442A. A suction means (not shown) is connected to the holding table 44A, and by operating the suction means, negative pressure can be generated on the holding surface 441A. As shown in Figures 7(a) and (b), the diameter of the holding surface 441A is set to be slightly larger than the diameter of the second wafer 10B. When the liquid supply process described above is carried out, the second wafer 10B is placed on the holding surface 441A of the holding table 44A so that the holding surface 441A is exposed in an annular shape on the outside of the second wafer 10B and held by suction. As a result, as shown in Figure 7(b), when liquid L is supplied from the nozzle body 212 of the liquid supply nozzle 21, any liquid L that flows around to the back surface 10Bb of the second wafer 10B is sucked out and removed at the outer circumference of the holding surface 441A, so that no liquid L remains on the back surface 10Bb side of the second wafer 10B. In this embodiment, the holding table 44A functions as a liquid removal means, and the liquid supply process and the liquid removal process are performed simultaneously.

[0045] (Modified example 2 of the liquid removal means) The liquid removal means employed in the liquid removal process of the present invention may also be a modified example 2, which includes the liquid suction means 46 shown in Figures 8(a) and 8(b). In the illustrated modified example 2, the liquid suction means 46 is positioned close to a holding table 44, the diameter of which is set to be smaller than that of the second wafer 10B. The liquid suction means 46 comprises a suction section 461 including a suction pad 462 exposed upward, and a suction passage 463 connected to the suction section 461, to which a suction means (not shown) is connected. By operating the suction means, negative pressure is generated on the suction pad 462. The height of the upper surface of the suction pad 462 is set to be the same as, or slightly lower than, the height of the upper surface of the holding surface 441 of the holding table 44. With this configuration, as shown in Figure 8(b), when the liquid supply process is performed to supply liquid L from the nozzle body 212 of the liquid supply nozzle 21 toward the interface 19 of the bonded wafer W to form a bonding force reduction region 19a, a liquid removal process can be performed to suck up and remove the liquid L that has flowed outward from the holding table 44, which rotates at a predetermined rotation speed V3, toward the back surface 10Bb of the second wafer 10B which overhangs outward, so that no liquid L remains on the back surface 10Bb side of the second wafer 10B. Note that if the modified example 2 shown in Figure 8 is adopted, the liquid removal process may be performed after the liquid supply process.

[0046] (Modified example 3 of the liquid removal method) The liquid removal means employed in the liquid removal process of the present invention may also be Modification 3, which includes the air injection means 47 shown in Figures 9(a) and (b). In the illustrated Modification 3, the air injection means 47 is positioned close to a holding table 44, the diameter of which is set to be smaller than that of the second wafer 10B. The air injection means 47 comprises an air injection section 471 including an injection hole 472 and an air passage 473 connected to the air injection section 471, and an air pumping means (not shown) is connected to the air passage 473. By operating the air pumping means, high-pressure air is injected from the injection hole 472. Preferably, the height of the upper surface of the injection hole 432 is set to be slightly lower than the height of the upper surface of the holding surface 441 of the holding table 44. With this configuration, as shown in Figure 9(b), after the liquid supply process is performed to supply liquid L from the nozzle body 212 of the liquid supply nozzle 21 toward the interface 19 of the bonded wafer W to form a bonding force reduction region 19a, a liquid removal process is performed to blow away the liquid L that has spread to the back surface 10Bb of the second wafer 10B that overhangs outward from the holding table 44, thereby removing the liquid L from the back surface 10Bb. As a result, no liquid L remains on the back surface 10Bb side of the second wafer 10B.

[0047] Although the liquid removal process can also be carried out by the modifications 1 to 3 described above, the following explanation will assume that the liquid removal process was carried out in the embodiment described with reference to Figures 4 and 6.

[0048] (Modified layer formation process) After the liquid supply and liquid removal steps described above have been performed, a modified layer formation step is performed in which the focal point of a laser beam is positioned 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 the beam is irradiated to form a ring-shaped modified layer. The modified layer formation step of this embodiment will be described in more detail with reference to Figure 10. In the wafer processing method according to the present invention, the modified layer formation step is not limited to being performed after the liquid supply and liquid removal steps described above, but may be performed simultaneously with the liquid supply and liquid removal steps, or even before the liquid supply and liquid removal steps.

[0049] When performing the modified layer formation process, the moving means 5 described above is activated to position the bonded wafer W, which is held by suction on the holding table 44, directly below the imaging means 7. The position of the outer edge where the chamfered portion 17A of the first wafer 10A is formed is detected, as well as the height of the upper surface of the back surface 10Ab of the first wafer 10A. An alignment is performed in which the processing position to be irradiated by positioning the pre-set focal point of the laser beam LB on the inside adjacent to the chamfered portion 17A formed on the outer edge of the first wafer 10A is detected, and this position is transmitted to and stored in the control means described above. Note that this alignment may be performed in conjunction with the alignment performed before the liquid supply process described above.

[0050] Based on the processing position information detected by the alignment described above, the moving means 5 is activated to move the holding table 41 so that the processing position set on 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 seen from Figure 10(a), the focal point of the laser beam LB is positioned inside the processing position on the first wafer 10A from the back surface 10Ab side of the first wafer 10A and irradiated, and the holding table 44 is rotated to form a ring-shaped modified layer 100 along the inside of the chamfered portion 17A of the first wafer 10A. In this embodiment, because a centering means 43 is provided, the center of the first wafer 10A and the rotation center of the holding table 44 coincide, so when forming the modified layer 100, it is not necessary to move the irradiation position of the laser beam LB or the holding table 44. However, if the above-described centering means 43 is not provided and the center of the first wafer 10A and the rotation center of the holding table 44 are misaligned, the direction and amount of the misalignment between the center of the first wafer 10A and the rotation center of the holding table 44 are detected by the above-described alignment, and the holding table 44 is oscillated in accordance with the amount and direction of the misalignment, thereby positioning the focal point of the laser beam at the desired processing position and forming a ring-shaped modified layer 100.

[0051] The modified layer 100 described above is preferably formed in multiple layers in the vertical direction, as shown in Figure 10. For example, the modified layer 100 shown in Figure 10 is composed of four modified layers in the vertical direction. When forming such a modified layer 100 including multiple layers, first, the focal point of the laser beam LB is positioned and irradiated so that the modified layer is formed inside the first wafer 10A, adjacent to the chamfered portion 17A, more specifically, at a predetermined distance (for example, 2.5 mm) inward from the outer peripheral edge of the first wafer 10A, for example, at a depth of 700 μm from the back surface 10Ab of the first wafer 10A, i.e., near the surface 10Aa, and the holding table 44 is rotated to form the first ring-shaped modified layer.

[0052] Subsequently, while rotating the holding table 44, the focal point is directed toward the back surface 10Ab side (upwards), and raised, for example, so that the depth to which the modified layer 100 is formed from the back surface 10Ab is 500 μm → 300 μm → 150 μm, thereby forming a ring-shaped modified layer 100 consisting of a total of four layers along the chamfered portion 17A, as shown in Figure 10. Note that the modified layer 100 shown in Figure 3(b) is shown conceptually for illustrative purposes, and the size and depth position of each layer do not correspond to the actual dimensions. With this, the modified layer formation process is completed. Note that the modified layer 100 described above is not limited to being formed of four layers, and the appropriate number of layers is set depending on the wavelength and output of the laser beam LB irradiated by the laser beam irradiation means 8, the thickness of the first wafer 10A, the material constituting the first wafer 10A, etc. Furthermore, the modified layers are not limited to being stacked vertically, but may be stacked so that they are inclined outwards as they go downwards in a cross-sectional view.

[0053] The laser processing conditions for forming the modified layer 100 described above 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

[0054] (Chamfering removal process) After the above-described modified layer formation process is carried out, a chamfer removal process is performed in which an external force is applied to the first wafer 10A to remove the chamfered portion 17A. The processing apparatus 1 of this embodiment is equipped with the above-described chamfer removal means 30, and it is possible to remove the chamfered portion 17A of the first wafer 10A using the chamfer removal means 30.

[0055] When performing the chamfer removal process, the modified layer 100 is formed on the excess outer peripheral region 18A of the first wafer 10A. Then, in order to remove the chamfer 17A, the moving means 5 is operated to position the holding table 44 below the chamfer removal section 38 of the chamfer removal means 30. Next, the arm 34 of the chamfer removal means 30 is lowered to bring the lower surface 382 of the chamfer removal section 38 into close contact with the back surface 10Ab of the first wafer 10A of the bonded wafer W. Next, the motor 36 of the chamfer removal means 30 operates the chamfer removal section 38, causing the blade 384 to protrude inward as shown by arrow R6 in Figure 11, and the blade 384 to enter the bonding force reduction region 19a formed on the outer peripheral side of the bonded wafer W. Simultaneously, the holding table 44 is rotated to break the outer peripheral excess region 18A, including the chamfered portion 17A, starting from the modified layer 100 described above.

[0056] After the outer peripheral excess region 18A, including the chamfered portion 17A, is broken, 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, and the wafer processing method of this embodiment is completed. After performing the wafer processing method of this embodiment on the bonded wafer W, it is placed in a suitable container (not shown) and transported to the next process.

[0057] Although the processing apparatus 1 of this embodiment is equipped with the chamfer removal means 30 described above, the 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, after forming the modified layer 100 described above on the first wafer 10A of the bonded wafer W, the bonded wafer W can be transported to the grinding apparatus 70 (only a portion is shown) shown in Figure 12(a), and the chamfer removal process can be carried out by grinding the back surface 10Ab of the first wafer 10A.

[0058] As shown in the figure, the grinding apparatus 70 includes a grinding means 72 for grinding and thinning a bonded wafer W held by suction on a chuck table 71. The grinding means 72 includes a rotary spindle 72a that is rotated by a rotary drive mechanism (not shown), a wheel mount 72b attached to the lower end of the rotary spindle 72a, and a grinding wheel 72c attached to the lower surface of the wheel mount 72b, with a plurality of grinding wheels 72d arranged in an annular pattern on the lower surface of the grinding wheel 72c.

[0059] After the modified layer W, which has been formed by the modified layer formation process, is transported to the grinding apparatus 70, the second wafer 10B is placed on the chuck table 71 with the back surface 10Ab of the first wafer 10A facing upwards and then held in place by suction.

[0060] Next, the rotating spindle 72a of the grinding means 72 is rotated at, for example, 6000 rpm in the direction indicated by arrow R7 in Figure 12(a), while the chuck table 71 is rotated at, for example, 300 rpm in the direction indicated by arrow R8. 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 0.1 μm / second, indicated by arrow R9. As a result, an external force is applied to the first wafer 10A, and as shown in Figure 12(b), the outer peripheral excess region 18A including the chamfered portion 17A where the bonding force reduction region 19a is formed is removed with the modified layer 100 as the starting point for separation, and a bonded wafer W is formed with the chamfered portion 17A removed, as shown on the left side in the figure. In other words, the process of applying an external force by performing grinding with the grinding device 70 described above becomes the chamfered portion removal process.

[0061] As described above, once the chamfered portion 17A has been removed from the first wafer 10A, grinding may be continued as necessary. Specifically, the grinding wheel 72c is fed downwards as indicated by arrow R9 at a grinding feed rate of, for example, 1.0 μm / second, and grinding is carried out while measuring the thickness of the bonded wafer W with a contact or non-contact measuring gauge (not shown) until the desired thickness is reached. Once the back surface 10Ab of the first wafer 10A has been ground by a predetermined amount and the bonded wafer W has reached the desired thickness, the grinding means 72 is stopped and retracted upwards to complete the grinding process. After the grinding process is completed, cleaning, drying, etc., are carried out as appropriate, details of which are omitted.

[0062] The chamfer removal process is not limited to being carried out by the chamfer removal means 30 and grinding device 70 described above. For example, the chamfer 17A may be removed by applying an external force to the first wafer 10A by spraying high-pressure air from the side toward the interface 19.

[0063] Although the bonded wafer W described above was formed by bonding a first wafer 10A and a second wafer 10B by siloxane bonding, the bonded wafer processed by the processing apparatus and wafer processing method of the present invention is not limited to wafers bonded by siloxane bonding. For example, the first wafer 10A and the second wafer 10B may be bonded by SiCN bonding via nitride bonding, by TEOS bonding which changes tetraethyl orthosilicate molecules into a solid with Si-O-Si bonding, or by ThOx bonding by silicon oxide film (SiO2) formed by oxidizing the surface of a silicon wafer by heating it in an oxygen atmosphere. In any case of bonding, the bonding force at the interface of the chamfered portions 17A and 18B can be weakened by the liquid supply step with the liquid L described above. Furthermore, the processing apparatus and wafer processing method of the present invention can also be applied to bonded wafer W that has been bonded after applying O2 plasma treatment or N2 plasma treatment as a pretreatment to the bonding surface forming the interface 19. [Explanation of symbols]

[0064] 1: Processing equipment 2: Base 3: Frame 4: Holding means 41:X-axis movable plate 42: Y-axis movable plate 43: Centering method 43a: Drive mechanism housing 431: Cylindrical member 44: Holding Table 44a: Rotation axis 44b: Electric motor 441: Holding surface 442: Frame 45: Center positioning mechanism 451: Lifting rod 452: Nails 452a: Tip 5: Means of transportation 5a:X-axis movement means 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: Effective area 17A: Chamfered part 18A: Outer perimeter surplus area 10B: Second wafer 17B: Chamfered part 19: Interface 19a: Bonding force reduction area 20:Fluid supply means 21: Fluid supply nozzle 211: Tip 211a:Aperture 212: Nozzle body 213: Rear end 22: Planar movement means 23: Means for moving in the thickness direction 24:Liquid supply mechanism 241: Liquid storage tank 242: Pump 243: Supply pipe 244: Three-way valve 245: Mizuhiki pipe 246 Flexible Tube 30: Chamfer removal means 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 100: Modified layer W: Bonded wafer

Claims

1. A wafer processing apparatus for processing a bonded wafer formed by joining a first wafer and a second wafer, A rotatable holding table with a holding surface for suction holding of 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 chamfered portion 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, A liquid supply means for supplying a liquid that weakens the bonding force at the interface of the chamfered portion where the first wafer and the second wafer are joined, A wafer processing apparatus comprising: a liquid removal means for removing liquid supplied by the liquid supply means that has seeped to the back surface of a second wafer.

2. The wafer processing apparatus according to claim 1, wherein the liquid removal means is configured such that the holding surface of the holding table is set to be slightly larger than that of the second wafer, and the liquid that has seeped around to the back surface of the second wafer is sucked out from the outer circumference of the holding surface to remove it.

3. The wafer processing apparatus according to claim 1, wherein the liquid removal means is configured such that the holding surface of the holding table is smaller than that of the second wafer, and the liquid that has seeped around to the back surface of the second wafer that overhangs from the holding table is sucked up and removed.

4. The wafer processing apparatus according to claim 1, wherein the liquid removal means is configured such that the holding surface of the holding table is smaller than that of the second wafer, and the liquid that has seeped around to the back surface of the second wafer that overhangs from the holding table is blown away with air to remove it.

5. The wafer processing apparatus according to claim 1, wherein the liquid supply means comprises a liquid supply nozzle having a tip for ejecting the liquid, a planar moving means for positioning the liquid supply nozzle by moving it toward and away from the interface of the chamfered portion in the planar direction of the bonded wafer, and a thickness direction moving means for moving the tip of the liquid supply nozzle toward the interface of the chamfered portion in the thickness direction of the bonded wafer.

6. The tip of the liquid supply nozzle is shaped like a hypodermic needle, and the amount of liquid supplied from the tip of the liquid supply nozzle is adjusted so that it does not fall due to surface tension. The wafer processing apparatus according to claim 5, wherein the position of the tip of the liquid supply nozzle in the planar direction and the thickness direction is adjusted to a position in which the liquid supplied from the tip of the liquid supply nozzle is absorbed by capillary action at the interface of the chamfered portion of the bonded wafer.

7. The holding table rotates at a speed at which the liquid supplied from the tip of the liquid supply nozzle is absorbed by capillary action against centrifugal force. The wafer processing apparatus according to claim 5, wherein the liquid removal means removes the liquid from the back surface of the second wafer by centrifugal force.

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

9. The wafer processing apparatus according to claim 1, wherein a centering means is provided to align the center of a bonded wafer held on the holding table with the center of the holding table.

10. The first wafer and the second wafer are joined by a Si-O-Si siloxane bond. The wafer processing apparatus according to claim 1, wherein the liquid that weakens the bonding force contains either water or ammonia and is supplied from the liquid supply means, and the bonding force is weakened by changing the Si-O-Si bond to a Si-OH-OH-Si bond.

11. A wafer processing method for processing a bonded wafer obtained by joining a first wafer and a second wafer using the wafer processing apparatus described in claim 1, A holding step in which the second wafer of the bonded wafer is held in place by a holding table through suction, A liquid supply step involves supplying a liquid to weaken the bonding force at the interface of the chamfered portion where the first wafer and the second wafer are joined, A liquid removal step is performed to remove any liquid that has seeped into the back surface of the second wafer during the liquid supply step. 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. A chamfering removal step involves applying an external force to the first wafer to remove the chamfered portion, A wafer processing method comprising the above.

Images