Processing method for wafer

Abstract

To provide a processing method for a wafer, preventing a crack occurring from a thin step part when a rear face of a wafer is ground to be thinned and enabling bonding of the wafer using the contour of the wafer as a reference when constituting a bonded wafer by stacking the wafer on the other wafer.SOLUTION: A processing method for a wafer comprising on a front face a device region 10A in which a plurality of devices are defined by predetermined dividing lines and an outer peripheral excessive region 10B with which a chamfered part 10C is formed on an outer periphery and which encloses the device region, forms an annular groove having a depth corresponding to a predetermined thickness on the front face of the wafer between the device region and the outer peripheral excessive region, before grinding a rear face of the waver to finish the wafer into the predetermined thickness. The method further includes: a step of disposing a substrate having a contour corresponding to a contour of the wafer on the front face of the wafer; a wafer holding step of holding the side of the substrate on a chuck table of a grinding device and exposing the rear face of the wafer; and a grinding step of grinding the rear face of the wafer to finish the wafer into the predetermined thickness.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for processing a wafer having a device region partitioned by a dicing line on a surface and an outer peripheral surplus region formed with a chamfer on the outer periphery and surrounding the device region.

Background Art

[0002] A wafer on which a plurality of devices such as ICs and LSIs are partitioned by dicing lines and formed on the surface is ground on the back surface to a predetermined thickness and then diced by a dicing device into individual device chips for use in electric devices such as mobile phones and personal computers.

[0003] A grinding device includes a chuck table for holding a wafer, grinding means rotatably provided with a grinding wheel having an annularly arranged grinding stone for grinding the wafer held on the chuck table, feeding means for feeding the grinding means, and measuring means for measuring the thickness of the wafer, and can process the wafer to a desired thickness.

[0004] However, a chamfer is formed on the outer periphery of the wafer. When the back surface of the wafer is ground and thinned, the chamfer becomes a sharp knife edge, cracks occur from the outer periphery and progress into the device region, damaging the device, and there is also a risk that the operator may be injured.

[0005] Therefore, the applicant has proposed a technique for removing the chamfer before grinding the back surface of the wafer (see Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, if the chamfered portion is completely removed from the outer periphery of the wafer, when laminating and bonding the wafers to form a bonded wafer with other wafers, a problem arises in that it becomes difficult to bond the wafers based on the outer shape of the wafer.

[0008] Also, the above problem can be avoided by providing a step with a depth corresponding to the finished thickness of the wafer from the outer periphery of the wafer and performing processing to leave a part of the chamfered portion. However, since the thickness of the stepped portion where the step is formed becomes thin, a load is applied to the stepped portion during bonding, and there is a problem that cracks occur from the outer periphery of the wafer and damage the device. In addition, when grinding the back surface of the wafer on which the stepped portion is formed, the stepped portion gradually becomes thinner, and when the finished thickness of the wafer is reached, cracks enter from the thinned stepped portion, and there is also a problem of damaging the device.

[0009] The present invention has been made in view of the above facts, and its main technical problem is to solve the problem that cracks enter from the thinned stepped portion and damage the device when the back surface of the wafer is ground and thinned, and to enable bonding based on the outer shape of the wafer when laminating and bonding the wafers to form a bonded wafer with other wafers. The object is to provide a method for processing a wafer.

Means for Solving the Problems

[0010] In order to solve the above main technical problem, according to the present invention, there is provided a method for processing a wafer having, on its surface, a device region partitioned by a planned division line and an outer peripheral surplus region formed with a chamfered portion on the outer periphery and surrounding the device region, the method including: an annular groove forming step of forming, on the surface of the wafer, an annular groove having a depth corresponding to the predetermined thickness at a boundary portion between the device region and the outer peripheral surplus region before grinding the back surface of the wafer to finish it to the predetermined thickness; a substrate disposing step of disposing a substrate having an outer shape corresponding to the outer shape of the wafer on the surface of the wafer; a wafer holding step of holding the substrate side on a chuck table of a grinding device to expose the back surface of the wafer; and a grinding step of grinding the back surface of the wafer to finish it to the predetermined thickness.

[0011] In the annular groove forming step, it is preferable to position a cutting blade at a boundary portion between the device region and the outer peripheral surplus region and form a cut annular groove at a depth corresponding to the predetermined thickness. Further, the substrate is preferably a protective member including either another wafer constituting a bonded wafer or a protective tape.

Effects of the Invention

[0012] The wafer processing method of the present invention is a wafer processing method having, on the surface, a device region in which a plurality of devices are partitioned by a dicing planned line and an outer peripheral surplus region in which a chamfered portion is formed on the outer periphery and surrounds the device region. The method includes an annular groove forming step of forming an annular groove having a depth corresponding to the predetermined thickness on the surface of the wafer at the boundary between the device region and the outer peripheral surplus region before grinding the back surface of the wafer to finish it to a predetermined thickness, a substrate disposing step of disposing a substrate having an outer shape corresponding to the outer shape of the wafer on the surface of the wafer, a wafer holding step of holding the substrate side on a chuck table of a grinding device and exposing the back surface of the wafer, and a grinding step of grinding the back surface of the wafer to finish it to a predetermined thickness. Therefore, when laminating and bonding a wafer that has been ground and thinned to a predetermined thickness to another wafer to form a bonded wafer, it is possible to perform the bonding based on the outer shape of the wafer. Further, even if a chamfered portion is left in the outer peripheral surplus region of the wafer, when laminating and bonding the wafer to another wafer to form a bonded wafer, the problem of the wafer being damaged due to a load being applied and the device being damaged is avoided. Furthermore, when grinding the back surface of the wafer, the step portion formed in the chamfered portion becomes thinner, and the problem of cracks entering from the step portion and damaging the wafer can also be avoided.

Brief Description of the Drawings

[0013]

Figure 1

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Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of a wafer processing method configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0015] In FIG. 1(a), as an example of a workpiece processed by the wafer processing method of the present embodiment, a silicon wafer 10 is shown. The illustrated wafer 10 has a diameter of, for example, 300 mm and a thickness of 700 μm, and a plurality of devices 12 are partitioned and formed on the surface 10a by division lines 14 for division. The wafer 10 has a device region 10A from the center where the above-described plurality of devices 12 are formed and an outer peripheral surplus region 10B surrounding the device region 10A on the surface 10a. In addition to FIG. 1(a), as shown in FIG. 1(b), a chamfered portion 10C formed in a curved surface shape is formed on the outer periphery of the outer peripheral surplus region 10B. In FIG. 1(a), an annular division line 16 (shown by a two-dot chain line) that divides the above-described device region 10A and outer peripheral surplus region 10B is described, but the division line 16 is described for convenience of explanation and is not actually attached to the surface 10a of the wafer 10. If the above-described wafer 10 is prepared as a workpiece, the wafer processing method of the present embodiment is carried out according to the procedure described below.

[0016] (Annular Groove Forming Step) When implementing the wafer processing method of the present embodiment, before grinding the back surface 10b of the wafer 10 to finish it to a predetermined thickness, an annular groove forming step is performed to form an annular groove with a depth corresponding to the predetermined thickness at the boundary between the above-described device region 10A and the outer peripheral surplus region 10B on the front surface 10a of the wafer 10. Note that the predetermined thickness is the finished thickness when grinding the back surface 10b of the wafer 10 in the grinding step described later, and is, for example, 400 μm.

[0017] To perform the annular groove forming step, the wafer 10 is transported to the cutting device 30 shown in FIG. 2 (only a part is shown). The cutting device 30 includes at least a cutting means 31 and a chuck table 32. The cutting means 31 includes a rotary shaft housing 33, a rotary shaft 34 rotatably held by the rotary shaft housing 33, and a cutting blade 35 fixed to the tip of the rotary shaft 34. An electric motor (not shown) for rotationally driving the rotary shaft 34 is disposed on the rear end side of the rotary shaft housing 33, and a suction means (not shown) is connected to the chuck table 32 to generate a negative pressure on the holding surface of the chuck table 32.

[0018] After transporting the wafer 10 to the above-described cutting device 30, the wafer 10 is placed on the chuck table 32 with the front surface 10a side facing upward, and the above-described suction means is operated to suck and hold it. Next, as shown in FIG. 2, the cutting blade 35 rotated at high speed in the direction indicated by the arrow R1 is positioned at the boundary between the device region 10A and the outer peripheral surplus region 10B and fed in, and the chuck table 32 is rotated in the direction indicated by the arrow R2 to form an annular groove 100 at the boundary between the device region 10A and the outer peripheral surplus region 10B. Note that the boundary is set on the annular dividing line 16 that divides the above-described device region 10A and the outer peripheral surplus region 10B, or in the outer peripheral surplus region 10B, between the dividing line 16 and the outer peripheral end where the chamfered portion 10C is formed, and is set, for example, about 2 mm inside from the outer peripheral end of the wafer 10.

[0019] As shown in FIGS. 3(a) and 3(b), an annular groove 100 is formed annularly along the boundary between the device region 10A and the outer peripheral surplus region 10B, and the annular groove forming step is completed. The depth of the annular groove 100 is set corresponding to a predetermined thickness, but it is preferably set to the finished thickness (400 μm) when the wafer 10 is ground in the grinding step described later, or a dimension slightly larger than the finished thickness. Further, the width of the annular groove 100 in the present embodiment is, for example, 40 μm. In the above-described embodiment, the annular groove 100 is formed along the boundary between the device region 10A and the outer peripheral surplus region 10B by the cutting device 30, but the method of forming the annular groove 100 is not limited thereto. For example, the annular groove 100 may be formed by irradiating the wafer 10 with a laser beam having a wavelength with absorbability and performing ablation processing along the boundary.

[0020] (Substrate Arrangement Step) As described above, when the annular groove forming step is completed, as shown in FIG. 4, a substrate 20 having an outer shape corresponding to the outer shape of the wafer 10 is prepared and arranged on the surface 10a of the wafer 10 to perform the substrate arrangement step of integrating them.

[0021] In the substrate arrangement step, as the substrate 20 arranged on the surface 10a of the wafer 10, for example, a resin protection tape having an adhesive force on the adhesion surface is selected, but the substrate in the present invention is not limited thereto. As the substrate in the present invention, a wafer having the same dimensions as the wafer 10 and having a plurality of devices formed on the surface partitioned by division planned lines may be used, and it may be laminated with the wafer 10 to form a bonded wafer. Further, for example, a rigid circular plate made of glass or steel may be used. At this time, the substrate 20 is selected to have an outer shape (diameter) corresponding to the outer shape (diameter) of the wafer 10 as described above, and can be bonded based on the outer shape of the wafer 10 and the outer shape of the substrate 20.

[0022] (Wafer Holding Process and Grinding Process) As described above, if the substrate placement process is carried out, then, in order to carry out the wafer holding process and the grinding process described later, it is transported, for example, to a grinding apparatus 1 as shown in FIG. 5.

[0023] The grinding apparatus 1 includes at least a chuck table 3 that holds the above-described wafer 10, a grinding means 4 that grinds the back surface 10b of the wafer 10 held by the chuck table 3, and a feed means 5 that feeds the grinding means 4 in the Z-axis direction (vertical direction).

[0024] As understood from FIG. 5, the chuck table 3 includes a holding surface 3a that sucks and holds the wafer 10, and a frame body 3b that supports and surrounds the holding surface 3a. The holding surface 3a is constituted by a porous member having air permeability, and a suction means (not shown) is connected to the frame body 3b. By operating the suction means, a negative pressure can be generated on the holding surface 3a to suck and hold the wafer 10.

[0025] The chuck table 3 is configured to be rotatable by a rotation drive means (not shown), and is moved by an X-axis movement means (not shown) housed inside the apparatus housing 2 to an arbitrary position in the X-axis direction, for example, a loading / unloading position for loading and unloading the wafer 10 on the front side in the figure, and a grinding position where grinding is performed directly below the grinding means 4.

[0026] The grinding means 4 includes a rotation shaft 4a, a grinding wheel 4b disposed at the lower end of the rotation shaft 4a, a plurality of grinding wheels 4c annularly disposed on the lower surface of the grinding wheel 4b, an electric motor 4d that rotates the rotation shaft 4a, a support portion 4e that supports the grinding means 4, and a Z-axis movement base 4f that is supported together with the support portion 4e in the Z-axis direction so as to be movable up and down on the vertical wall portion 2a of the apparatus housing 2. The feed means 5 converts the rotational movement of the pulse motor 5a into a linear movement via a ball screw 5b rotated by the pulse motor 5a and transmits it to the Z-axis movement base 4f, making it possible to move the grinding means 4 to an arbitrary position in the Z-axis direction (vertical direction).

[0027] Grinding water L is supplied from a grinding water supply source (not shown) to the upper end portion 4a' of the rotating shaft 4a, and via the inside of the rotating shaft 4a, it is supplied to the wafer 10 held by the chuck table 3 and the grinding wheel 4c that grinds the wafer 10. The grinding apparatus 1 includes control means (not shown), and each of the above-described operating parts is controlled by a control signal instructed from the control means.

[0028] The grinding apparatus 1 generally has the configuration as described above, and the wafer holding step and the grinding step performed using the grinding apparatus 1 shown in the drawings will be described below.

[0029] If the wafer 10, which is formed by disposing the substrate 20 on the surface 10a and integrating them, is transported to the grinding apparatus 1, then as shown in FIG. 5, the chuck table 3 is moved to the loading / unloading position on the front side, and as shown in FIG. 6, with the substrate 20 side facing downward, the back surface 10b of the wafer 10 is exposed upward and placed on the holding surface 3a of the chuck table 3, and suction means (not shown) is operated to hold it (wafer holding step).

[0030] Next, the above-described X-axis moving means is operated to position the chuck table 3 that sucks and holds the wafer 10 at a grinding position where grinding is performed directly below the grinding means 4. Then, as shown in FIG. 7, the rotating shaft 4a of the grinding means 4 is rotated in the direction indicated by the arrow R3 at a predetermined rotational speed (for example, 6000 rpm), and the chuck table 3 is rotated in the direction indicated by the arrow R4 at a predetermined rotational speed (for example, 300 rpm) by operating rotational driving means (not shown).

[0031] Next, the above-described feeding means 5 is operated to lower the grinding means 4 in the direction indicated by the arrow R5, bring the grinding wheel 4c into contact with the back surface 10b of the wafer 10, and operate the above-described grinding water supply means to supply the grinding water L to the grinding wheel 4c and the back surface 10b of the wafer 10 via the rotating shaft 4a. Then, while operating a thickness measuring means (not shown) to measure the thickness of the wafer 10, the wafer 10 is ground and thinned until it reaches a predetermined thickness (400 μm) while the grinding means 4 is fed at a predetermined speed (for example, 1.0 μm / second) (grinding step). Thus, the method for processing a wafer according to the present embodiment is completed.

[0032] When the above-described grinding step is performed by the grinding apparatus 1 of the present embodiment, as shown in FIG. 8(a), an annular groove 100 appears on the back surface 10b side so as to separate a central region 10A' corresponding to the device region 10A and an outer peripheral region 10B' corresponding to the outer peripheral surplus region 10B while being integrally held by the substrate 20. In addition to FIG. 8(a), as understood from FIG. 8(b), a chamfered portion 10C of the outer peripheral region 10B' remains in a state where the entire wafer 10 is integrally held by the substrate 20. Therefore, according to the above-described embodiment, when grinding the back surface 10b of the wafer 10, the step portion formed in the chamfered portion 10C becomes thinner, and a crack enters from the step portion, thereby avoiding the problem of damaging the wafer 10.

[0033] Further, according to the above-described embodiment, even when the grinding step is performed, the outer peripheral surplus region 10B of the wafer 10 is separated from the device region 10A by the annular groove 100 while the chamfered portion 10C remains in the outer peripheral region 10B' of the wafer 10. Therefore, when laminating the above-described wafer 10 on another wafer to form a bonded wafer, for example, if a protective tape is attached to the back surface 10b side of the wafer 10 and the substrate 20 disposed on the front surface 10a is peeled off, it becomes possible to bond the wafer 10 to another wafer based on the outer shape of the wafer 10, and when laminating the wafer 10 on another wafer to form a bonded wafer, the problem of damaging the wafer 10 and damaging the device 12 due to a load being applied is avoided.

[0034] Furthermore, when the substrate 20 is another wafer laminated on the wafer 10 to form a bonded wafer, after the above-described grinding process is completed, by removing the outer peripheral region 10B' separated by the annular groove 100, the chamfered portion 10C on the wafer 10 side that constitutes the bonded wafer is removed. In that case, in the substrate disposition process, since another wafer having an outer shape corresponding to the outer shape of the wafer 10 is prepared as the substrate 20, a bonded wafer can be formed by bonding based on the outer shape of the wafer 10 and the outer shape of the substrate 20. Even when the back surface 10b of the wafer 10 is ground by the grinding process for such a bonded wafer, the step portion formed in the chamfered portion 10C becomes thin, and cracks enter from the step portion, damaging the wafer 10. This problem is avoided.

Description of Signs

[0035] 1: Grinding device 2: Device housing 3: Chuck table 4: Grinding means 4a: Rotation axis 4b: Grinding wheel 4c: Grinding stone 4d: Electric motor 4e: Support portion 4f: Z-axis movement base 5: Feeding means 10: Wafer 10a: Front surface 10b: Back surface 10A: Device region 10A': Central region 10B: Outer peripheral surplus region 10B': Outer peripheral region 10C: Chamfered portion 12: Device 14: Scribing line 16: Division line 20: Substrate 30: Cutting device 31: Cutting means 32: Chuck table 33: Rotating shaft housing 34: Rotating shaft 35: Cutting blade 100: Annular groove

Claims

1. A method for processing a wafer having a device region partitioned by a division planned line on a surface thereof and an outer peripheral surplus region formed with a chamfered portion on the outer periphery and surrounding the device region, an annular groove forming step of forming an annular groove having a depth corresponding to the predetermined thickness on the surface of the wafer at a boundary portion between the device region and the outer peripheral surplus region before grinding the back surface of the wafer to finish it to the predetermined thickness; a substrate disposing step of disposing a substrate having an outer shape corresponding to the outer shape of the wafer on the surface of the wafer; a wafer holding step of holding the substrate side on a chuck table of a grinding device to expose the back surface of the wafer; a grinding step of grinding the back surface of the wafer to finish it to the predetermined thickness; A method for processing a wafer, comprising the above steps.

2. The method for processing a wafer according to claim 1, wherein in the annular groove forming step, a cutting blade is positioned at a boundary portion between the device region and the outer peripheral surplus region and a cut annular groove is formed at a depth corresponding to the predetermined thickness.

3. The method for processing a wafer according to claim 1, wherein the substrate is a protective member including either another wafer constituting a bonded wafer or a protective tape.

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