Method for processing wafers and method for manufacturing device chips

Abstract

The present invention provides a wafer processing method that enables the uniform formation of a resin layer on the ground surface of a wafer after grinding. [Solution] The wafer processing method includes a chamfer removal step of removing at least a portion of the chamfered portion 8 of the first wafer 2 in an annular shape along the outer circumference of the first wafer 2; a bonding step of bonding the first surface 2a of the first wafer 2 to the second wafer 26; a grinding step of grinding the second surface 2b of the first wafer 2 with a grinding wheel 50 equipped with grinding wheels 52 arranged in an annular shape after the chamfer removal step and the bonding step; a corner processing step of processing the corner portion 2c of the outer peripheral edge on the second surface 2b side of the first wafer 2 that was ground in the grinding step so that the thickness gradually decreases toward the radially outward direction; and a resin layer forming step of forming a resin layer by applying a liquid resin to the second surface 2b of the first wafer 2 after the corner processing step.

Description

Technical Field

[0001] The present invention relates to a wafer processing method and a device chip manufacturing method.

Background Art

[0002] Some wafers, in which a plurality of devices are formed on a first surface, are provided with a chamfered portion at the outer peripheral edge thereof. When the second surface side of the wafer provided with the chamfered portion is ground to thin the wafer, the chamfered portion becomes a sharp edge. This causes a problem that cracks are likely to extend inward from the outer periphery of the wafer, increasing the risk of device damage. Accordingly, a known technique removes the chamfered portion in advance to prevent sharp edges from being generated even when the wafer is ground (see, for example, Patent Document 1). Also, for a bonded wafer in which a first wafer and a second wafer are bonded together, the chamfered portion of the first wafer is removed in advance, and then the first wafer is ground and thinned.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when a liquid resin is applied to the ground surface of a wafer after grinding to form a resin layer, there is a problem in that the thickness of the resin layer is not uniform. As shown in Figure 1, in the wafer W after grinding, the corner W3 between the ground surface W1 and the side surface W2 is at a right angle. Due to the influence of surface tension acting on the liquid resin, the resin layer R bulges at the outer edge of the wafer W, forming a portion Ra with a relatively large thickness of resin layer R and a portion Rb with a relatively small thickness of resin layer R. If the thickness of the resin layer R is not uniform, for example, if the resin layer R is a resist film, exposure defects or an increase in the time required to remove the resist film may occur.

[0005] The object of the present invention is to provide a wafer processing method and a device chip manufacturing method that can uniformly form a resin layer on the ground surface of the wafer after grinding. [Means for solving the problem]

[0006] According to the present invention, the following wafer processing method is provided that solves the above problems. That is, A wafer processing method for processing a first wafer having a first surface and a second surface opposite to the first surface, and having a chamfered portion formed on its outer edge, A chamfer removal step of removing at least a portion of the chamfered portion of the first wafer in an annular shape along the outer circumference of the first wafer, A bonding step of bonding the first surface of the first wafer to the second wafer, A grinding step is performed after the chamfer removal step and the bonding step, in which the second surface of the first wafer is ground with a grinding wheel equipped with annularly arranged grinding wheels, A corner processing step is performed on the corner of the outer edge of the second surface side of the first wafer that was ground in the grinding step, such that the thickness gradually decreases toward the radially outward direction. A wafer processing method is provided, which includes a resin layer forming step, after the corner processing step, a step of forming a resin layer by applying a liquid resin to the second surface of the first wafer.

[0007] Preferably, the joining step is performed after the chamfer removal step. The joining step may also be performed before the chamfer removal step.

[0008] In the corner processing step, it is preferable to process the corner with the grinding wheel by moving the grinding wheel and the first wafer relative to each other. Alternatively, in the corner processing step, the corner may be processed with the cutting blade by moving an annular cutting blade having a cutting edge on its outer circumference relative to the first wafer. In the corner processing step, the second surface of the first wafer may be polished and the corner processed using a polishing pad.

[0009] According to the present invention, the following method for manufacturing a device chip is provided that solves the above problems. That is, A method for manufacturing chips, A chamfer removal step of a first wafer having a first surface on which devices are formed in each of a plurality of regions demarcated by a plurality of division lines, and a second surface opposite to the first surface, and having a chamfer formed at its outer edge, wherein at least a portion of the chamfer is removed in an annular manner along the outer edge of the first wafer, A bonding step of bonding the first surface of the first wafer to the second wafer, A grinding step is performed after the chamfer removal step and the bonding step, in which the second surface of the first wafer is ground with a grinding wheel equipped with annularly arranged grinding wheels, A corner processing step is performed on the corner of the outer edge of the second surface side of the first wafer that was ground in the grinding step, such that the thickness gradually decreases toward the radially outward direction. A resin layer forming step is performed after the corner processing step, by applying a liquid resin to the second surface of the first wafer to form a resin layer. A method for manufacturing a device chip is provided, which includes, after the resin layer formation step, a division step of dividing the first wafer and the second wafer along the planned division line of the first wafer to manufacture a device chip. [Effects of the Invention]

[0010] The wafer processing method of the present invention is A wafer processing method for processing a first wafer having a first surface and a second surface opposite to the first surface, and having a chamfered portion formed on its outer edge, A chamfer removal step of removing at least a portion of the chamfered portion of the first wafer in an annular shape along the outer circumference of the first wafer, A bonding step of bonding the first surface of the first wafer to the second wafer, A grinding step is performed after the chamfer removal step and the bonding step, in which the second surface of the first wafer is ground with a grinding wheel equipped with annularly arranged grinding wheels, A corner processing step is performed on the corner of the outer edge of the second surface side of the first wafer that was ground in the grinding step, such that the thickness gradually decreases toward the radially outward direction. The process includes a resin layer forming step, in which a liquid resin is applied to the second surface of the first wafer after the corner processing step to form a resin layer. This allows for the uniform formation of a resin layer on the ground surface of the wafer after grinding.

[0011] The method for manufacturing a device chip of the present invention is: A chamfer removal step of a first wafer having a first surface on which devices are formed in each of a plurality of regions demarcated by a plurality of division lines, and a second surface opposite to the first surface, and having a chamfer formed at its outer edge, wherein at least a portion of the chamfer is removed in an annular manner along the outer edge of the first wafer, A bonding step of bonding the first surface of the first wafer to the second wafer, A grinding step is performed after the chamfer removal step and the bonding step, in which the second surface of the first wafer is ground with a grinding wheel equipped with annularly arranged grinding wheels, A corner processing step is performed on the corner of the outer edge of the second surface side of the first wafer that was ground in the grinding step, such that the thickness gradually decreases toward the radially outward direction. after the corner processing step, a resin layer forming step of forming a resin layer by applying a liquid resin to the second surface of the first wafer, and after the resin layer forming step, a dividing step of dividing the first wafer and the second wafer along the predetermined dividing lines of the first wafer to manufacture device chips, so that the resin layer can be uniformly formed on the ground surface of the ground wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] [Figure 1] A schematic diagram in the case where a resin layer is formed on a ground surface of a wafer according to the related art. [Figure 2] A perspective view of a first wafer. [Figure 3] (a) A schematic diagram showing a chamfered portion removing step, and (b) a perspective view of the first wafer in which a part of a chamfered portion is annularly removed along the outer periphery. [Figure 4] (a) A schematic diagram showing a bonding step, and (b) a cross-sectional view of a bonded wafer in which the first wafer and a second wafer are bonded together. [Figure 5] (a) A schematic diagram showing a grinding step, and (b) a perspective view of the bonded wafer after the grinding step. [Figure 6] (a) A schematic diagram in the case where a corner processing step is performed by a grinding wheel, (b) a partial cross-sectional view of the bonded wafer in which an inclined surface is formed at a corner portion, and (c) a partial cross-sectional view of the bonded wafer in which a curved surface is formed at a corner portion. [Figure 7] A schematic diagram in the case where the corner processing step is performed by a cutting blade. [Figure 8] A schematic diagram in the case where the corner processing step is performed by a polishing pad. [Figure 9] (a) A schematic diagram showing the resin layer forming step, (b) a partial cross-sectional view of the bonded wafer in the case where a resin layer is formed on the bonded wafer having the inclined surface at the corner portion, and (c) a partial cross-sectional view of the bonded wafer in the case where a resin layer is formed on the bonded wafer having the curved surface at the corner portion. [Figure 10](a) Schematic diagram of the case where the bonding step is performed before the chamfer removal step, (b) cross-sectional view of the bonded wafer, (c) Schematic diagram of the case where the chamfer removal step is performed after the bonding step. [Figure 11] (a) A partial cross-sectional view of a cutting blade with a first side surface inclined; (b) A partial cross-sectional view of a cutting blade with both the first and second side surfaces inclined; (c) A partial cross-sectional view of a first wafer in which a portion of the chamfered area has been removed in an annular manner along the outer circumference by the cutting blade shown in (a) or (b); (d) A partial cross-sectional view of a bonded wafer after a grinding step has been performed on the first wafer shown in (c); (e) A partial cross-sectional view of a bonded wafer after a corner processing step has been performed on the bonded wafer shown in (d); (f) A partial cross-sectional view of a bonded wafer after a resin layer formation step has been performed on the bonded wafer shown in (e). [Figure 12] (a) Partial cross-sectional view of a bonded wafer, (b) Schematic plan view of the bonded wafer shown in (a) when the chamfer removal step is performed on the first wafer, (c) Partial cross-sectional view of a bonded wafer in which the entire chamfer of the first wafer has been removed in an annular shape along the outer circumference by the method shown in (b), (d) Partial cross-sectional view of a bonded wafer when the grinding step is performed on the bonded wafer shown in (c), (e) Partial cross-sectional view of a bonded wafer when the corner processing step is performed on the bonded wafer shown in (d), and (f) Partial cross-sectional view of a bonded wafer when the resin layer formation step is performed on the bonded wafer shown in (e). [Figure 13] (a) A schematic diagram showing the chamfer removal step performed on the first wafer before bonding by irradiation with a laser beam, and (b) A schematic diagram showing the chamfer removal step performed on the first wafer of the bonding wafer by irradiation with a laser beam. [Modes for carrying out the invention]

[0013] Hereinafter, preferred embodiments of the wafer processing method and device chip manufacturing method according to the present invention will be described with reference to the drawings.

[0014] [Wafer 1, Part 2] Figure 2 shows a disc-shaped first wafer 2 processed by the method of the present invention. The first wafer 2 has a circular first surface 2a and a circular second surface 2b opposite to the first surface 2a. The first wafer 2 can be formed from a semiconductor material such as silicon or silicon carbide. The first surface 2a of the first wafer 2 is divided into multiple regions by a plurality of division lines 4, and a device 6 such as an IC (Integrated Circuit) is formed in each of the divided regions. In addition, a chamfered portion 8 and a notch 10 indicating the crystal orientation are formed on the outer edge of the first wafer 2.

[0015] [Chamfered area removal step] In this embodiment, first, a chamfer removal step is performed in which at least a portion of the chamfered portion 8 of the first wafer 2 is removed in an annular shape along the outer circumference of the first wafer 2.

[0016] (Cutting device 12) The chamfer removal step can be performed, for example, using the cutting device 12 shown in Figure 3(a). The cutting device 12 includes a chuck table 14 for holding the workpiece and a cutting unit 16 for cutting the workpiece held on the chuck table 14.

[0017] (Chuck table 14 of cutting device 12) A disc-shaped suction chuck 18 is positioned at the upper end of the chuck table 14. The suction chuck 18 is made of a porous material such as porous ceramics and is connected to a suction pump (not shown). The chuck table 14 generates a suction force on the upper surface of the suction chuck 18 using the suction pump, and holds the workpiece placed on the upper surface of the chuck table 14 by suction. The chuck table 14 is also rotatable about an axis Z1 that passes through the center of the suction chuck 18 and extends in the Z-axis direction.

[0018] (Cutting unit 16 of cutting device 12) The cutting unit 16 includes a spindle housing 20 that is movable in the Y-axis and Z-axis directions, a spindle 22 supported by the spindle housing 20 so as to be rotatable about an axis Y1 extending in the Y-axis direction, and an annular cutting blade 24 fixed to the tip of the spindle 22. The cutting edge on the outer circumference of the cutting blade 24 may be made of abrasive grains such as diamond bonded by a bonding material such as a metal bond or a resin bond. The thickness of the cutting edge of the cutting blade 24 is preferably such that at least a portion of the chamfered portion 8 of the first wafer 2 can be removed in an annular shape along the outer circumference of the first wafer 2 (for example, about 2 mm to 3 mm).

[0019] In the chamfer removal step, first, the first wafer 2 is held by suction on the upper surface of the chuck table 14 with the first surface 2a facing upwards. At this time, the center of the first wafer 2 is aligned with the axis Z1. Next, the spindle housing 20 or the chuck table 14 is moved to position the cutting blade 24 above the chamfer 8 of the first wafer 2. Then, the cutting blade 24 is rotated in the direction indicated by arrow R1 in Figure 3(a). Then, the cutting edge of the cutting blade 24 is driven into the chamfer 8 of the first wafer 2 to a depth greater than or equal to a predetermined finished thickness, and cutting fluid (e.g., pure water) is supplied while the chuck table 14 is rotated in the direction indicated by arrow R2 in Figure 3(a). This allows a portion of the chamfer 8 (in the example shown in Figure 3(b), a portion on the first surface 2a side) to be removed in an annular shape along the outer circumference of the first wafer 2. In Figure 3(b), the portion where a portion of the chamfer 8 has been removed is indicated by reference numeral 8a.

[0020] [Joining step] After performing the chamfer removal step, a bonding step is performed to bond the first surface 2a of the first wafer 2 to the second wafer 26, as shown in Figures 4(a) and 4(b).

[0021] The configuration of the second wafer 26 bonded to the first wafer 2 may be the same as that of the first wafer 2. In this embodiment, as shown in Figure 4(a), the disc-shaped second wafer 26 has a circular first surface 26a and a circular second surface 26b opposite to the first surface 26a. The diameter of the second wafer 26 is the same as that of the first wafer 2. The material of the second wafer 26 is the same as that of the first wafer 2 (for example, silicon or silicon carbide). The first surface 26a of the second wafer 26 is divided into multiple regions by a plurality of division lines 28, and a device 30 is formed in each of the divided regions. A chamfered portion 32 is formed on the outer edge of the second wafer 26, and a notch 34 indicating the crystal orientation is formed therein. Furthermore, the second wafer 26 does not have to have the same configuration as the first wafer 2. For example, the device 30 may not be formed on the first surface 26a, or the material, diameter, etc. of the second wafer 26 may differ from those of the first wafer 2.

[0022] In the bonding step, the first surface 2a of the first wafer 2 and the first surface 26a of the second wafer 26 are bonded together. When bonding, the notch 10 of the first wafer 2 and the notch 34 of the second wafer 26 are aligned, and the crystal orientation of the first wafer 2 and the crystal orientation of the second wafer 26 are matched. The bonding method for the first and second wafers 2 and 26 may be a known method. Hereinafter, the bonded wafers 2 and 26 will be referred to as "bonded wafer 36".

[0023] [Grinding step] After performing the chamfer removal step, a grinding step is performed in which the second surface 2b of the first wafer 2 is ground using a grinding wheel equipped with grinding wheels arranged in an annular shape.

[0024] (Grinding device 38) The chamfer removal step can be performed, for example, using the grinding device 38 shown in Figure 5(a). The grinding device 38 includes a chuck table 40 for holding the workpiece and a grinding unit 42 for grinding the workpiece held on the chuck table 40.

[0025] (Chuck table 40 of grinding machine 38) A disc-shaped suction chuck 44 is positioned at the upper end of the chuck table 40. The suction chuck 44 is made of a porous material such as porous ceramics and is connected to a suction pump (not shown). The chuck table 40 generates a suction force on the upper surface of the suction chuck 44 using the suction pump, and holds the workpiece placed on the upper surface of the chuck table 40 by suction. The chuck table 40 is also rotatable about an axis Z2 that extends in the Z-axis direction through the center of the suction chuck 44.

[0026] (Grinding unit 42 of grinding device 38) The grinding unit 42 comprises a spindle 46 that is rotatable about an axis Z3 extending in the Z-axis direction, a disc-shaped wheel mount 48 fixed to the lower end of the spindle 46, and an annular grinding wheel 50 fastened to the lower surface of the wheel mount 48. Multiple grinding wheels 52 are fixed to the peripheral edge of the lower surface of the grinding wheel 50, arranged in an annular pattern at intervals in the circumferential direction. The grinding wheels 52 may be made of abrasive grains such as diamonds bonded together with a bonding material such as a metal bond or a resin bond.

[0027] In the grinding step, first, the second surface 2b of the first wafer 2 is turned upward, and the bonded wafer 36 is held by suction on the upper surface of the chuck table 40. At this time, the center of the first wafer 2 is aligned with the axis Z2. Next, the spindle 46 is rotated in the direction indicated by arrow R3 in Figure 5(a), and the chuck table 40 is rotated in the direction indicated by arrow R4 in Figure 5(a). Then, the spindle 46 is lowered, and the grinding wheel 52 is brought into contact with the second surface 2b of the first wafer 2, and grinding water (for example, pure water) is supplied. After that, the spindle 46 is lowered at a predetermined grinding feed rate. As a result, as shown in Figure 5(b), the second surface 2b of the first wafer 2 is ground, and the first wafer 2 can be thinned to a predetermined finished thickness. Furthermore, in the chamfer removal step, the chamfer 8 on the first surface 2a side of the first wafer 2 is removed to a depth greater than or equal to a predetermined finished thickness. Therefore, by performing the grinding step, the chamfer 8 of the first wafer 2 is completely removed.

[0028] [Corner machining step] After performing the grinding step, a corner processing step is performed on the corner portion 2c of the outer edge of the second surface 2b side of the first wafer 2 that was ground in the grinding step, so that the thickness gradually decreases toward the radially outward direction.

[0029] (Corner processing with grinding device 38) The corner processing step can be performed, for example, using the grinding device 38 described above. When performing the corner processing step using the grinding device 38, with the bonded wafer 36 held by the chuck table 40, the spindle 46 or the chuck table 40 is moved to position the grinding wheel 52 radially outward of the first wafer 2, as shown in Figure 6(a). Next, the spindle 46 is rotated in the direction indicated by arrow R3, and the chuck table 40 is rotated in the direction indicated by arrow R4. Then, the corner 2c is processed by the grinding wheel 52 of the grinding wheel 50 by moving the grinding wheel 50 and the first wafer 2 relative to each other. That is, the grinding wheel 50 is moved straight in the direction indicated by arrow A1, or the chuck table 40 is moved straight in the direction indicated by arrow A2, bringing the grinding wheel 52 into contact with the corner 2c of the outer peripheral edge on the second surface 2b side of the first wafer 2, and grinding water is supplied. As a result, as shown in Figure 6(b), the corners 2c at the outer edge can be ground down and processed (chamfered) so that the thickness of the first wafer 2 gradually decreases toward the radially outward direction.

[0030] When performing the corner processing step using the grinding device 38, instead of moving in the direction indicated by arrow A1 or arrow A2, the grinding wheel 50 is moved in the direction indicated by arrow A3 in an arc, or the chuck table 40 is moved in the direction indicated by arrow A4 in an arc, bringing the grinding wheel 52 into contact with the corner 2c of the outer peripheral edge on the second surface 2b side of the first wafer 2, and grinding water is supplied. As a result, as shown in Figure 6(c), the corner 2c of the outer peripheral edge is ground, and the corner 2c is processed (R-chamfered) so that the thickness gradually decreases toward the radially outward direction of the first wafer 2.

[0031] (Corner processing with cutting device 12) The corner processing step can also be performed using the cutting device 12 described above. When performing the corner processing step using the cutting device 12, first, the second surface 2b of the first wafer 2 is turned upward, and the bonded wafer 36 is held by suction on the upper surface of the chuck table 14. At this time, the center of the first wafer 2 is aligned with the axis Z1. Next, the spindle housing 20 or the chuck table 14 is moved to position the cutting blade 24 radially outward of the first wafer 2, as shown in Figure 7. Next, the cutting blade 24 is rotated in the direction indicated by arrow R1, and the chuck table 14 is rotated in the direction indicated by arrow R2. Then, the corner 2c is processed with the cutting edge of the cutting blade 24 by moving the cutting blade 24 and the first wafer 2 relative to each other. Specifically, the cutting blade 24 is moved straight in the direction indicated by arrow A5, or the chuck table 14 is moved straight in the direction indicated by arrow A6, bringing the cutting edge of the cutting blade 24 into contact with the corner 2c of the outer peripheral edge on the second surface 2b side of the first wafer 2, and supplying cutting fluid. This allows the corner 2c of the outer peripheral edge to be cut, and the corner 2c can be processed (C-chamfered) so that the thickness gradually decreases toward the radially outward direction of the first wafer 2 (see Figure 6(b)).

[0032] When performing the corner processing step using the cutting device 12, instead of moving in the direction indicated by arrow A5 or arrow A6, the cutting blade 24 is moved in an arc in the direction indicated by arrow A7, or the chuck table 14 is moved in an arc in the direction indicated by arrow A8, so that the cutting edge of the cutting blade 24 comes into contact with the corner 2c of the outer peripheral edge on the second surface 2b side of the first wafer 2, and cutting fluid is supplied. This cuts the corner 2c of the outer peripheral edge, and processing (R-chamfering) is performed on the corner 2c so that the thickness gradually decreases toward the radially outward direction of the first wafer 2 (see Figure 6(c)).

[0033] (polishing device 54) The corner machining step can also be performed using the polishing device 54 shown in Figure 8. The polishing device 54 includes a chuck table 56 for holding the workpiece and a polishing unit 58 for grinding the workpiece held on the chuck table 56.

[0034] (Chuck table 56 of polishing device 54) A disc-shaped suction chuck 60 is positioned at the upper end of the chuck table 56. The suction chuck 60 is made of a porous material such as porous ceramics and is connected to a suction pump (not shown). The chuck table 56 generates a suction force on the upper surface of the suction chuck 60 using the suction pump, and holds the workpiece placed on the upper surface of the chuck table 56 by suction. The chuck table 56 is also rotatable about an axis Z4 that extends in the Z-axis direction through the center of the suction chuck 60.

[0035] (Polishing unit 58 of polishing device 54) The polishing unit 58 includes a spindle 62 that is rotatable about an axis Z5 extending in the Z-axis direction, a disc-shaped pad mount 64 fixed to the lower end of the spindle 62, and a disc-shaped polishing pad 66 fixed to the lower surface of the pad mount 64. As shown in Figure 8, the diameter of the polishing pad 66 is larger than the diameter of the bonded wafer 36. The polishing pad 66 may be formed from a synthetic resin such as polyurethane containing abrasive grains such as diamond, or from a nonwoven fabric such as felt containing abrasive grains such as diamond.

[0036] (Corner processing with polishing device 54) When performing the corner processing step using the polishing device 54, first, the bonded wafer 36 is held by suction on the upper surface of the chuck table 56 with the second surface 2b of the first wafer 2 facing upwards. Next, the spindle 62 is rotated in the direction indicated by arrow R5, and the chuck table 56 is rotated in the direction indicated by arrow R6. Then, the spindle 62 is lowered, and the polishing pad 66 is pressed against the second surface 2b of the first wafer 2 to polish the second surface 2b of the first wafer 2. As a result, as shown in an enlarged view in Figure 8, the polishing pad 66 elastically deforms at the corner 2c of the outer peripheral edge on the second surface 2b side of the first wafer 2 so that it slopes downward toward the radially outward direction of the first wafer 2. As a result, the second surface 2b and the corner 2c are polished, and the corner 2c is processed (C-chamfering or R-chamfering) so that the thickness gradually decreases toward the radially outward direction of the first wafer 2. During polishing, polishing fluid may be supplied between the polishing pad 66 and the second surface 2b.

[0037] [Resin layer formation step] After performing the corner processing step, a resin layer formation step is performed in which a resin layer is formed by applying liquid resin to the second surface 2b of the first wafer 2.

[0038] (Liquid resin supply device 68) The resin layer formation step can be carried out, for example, using the liquid resin supply device 68 shown in Figure 9(a). The liquid resin supply device 68 includes a chuck table 70 for holding the workpiece and a liquid resin supply unit 72 for supplying liquid resin to the workpiece held on the chuck table 70.

[0039] (Chuck table 70 of liquid resin supply device 68) A disc-shaped suction chuck 74 is positioned at the upper end of the chuck table 70. The suction chuck 74 is made of a porous material such as porous ceramics and is connected to a suction pump (not shown). The chuck table 70 generates a suction force on the upper surface of the suction chuck 74 using the suction pump, and holds the workpiece placed on the upper surface of the chuck table 70 by suction. The chuck table 70 is also rotatable about an axis Z6 that extends in the Z-axis direction through the center of the suction chuck 74.

[0040] (Liquid resin supply unit 72 of liquid resin supply device 68) The liquid resin supply unit 72 includes a tank (not shown) for storing liquid resin, a pump (not shown) for dispensing the liquid resin from the tank, and a supply pipe 76 for supplying the liquid resin dispensed by the pump to the upper surface of the workpiece held on the chuck table 70.

[0041] In the resin layer formation step, first, the bonded wafer 36 is held by suction on the upper surface of the chuck table 70 with the second surface 2b of the first wafer 2 facing upwards. At this time, the center of the first wafer 2 is aligned with the axis Z6. Next, the outlet 76a of the supply pipe 76 of the liquid resin supply unit 72 is positioned above the center of the first wafer 2. Then, the chuck table 70 is rotated in the direction indicated by the arrow R6, and liquid resin 78 is dripped onto the first wafer 2 from the supply pipe 76 of the liquid resin supply unit 72. As a result, the liquid resin 78 that has been dripped onto the second surface 2b of the first wafer 2 is spread over the entire second surface 2b of the first wafer 2 by centrifugal force. After that, the liquid resin 78 is solidified to form a resin layer 80 on the second surface 2b of the first wafer 2 (see Figures 9(b) and 9(c)).

[0042] As described above, in this embodiment, the corner portion 2c of the outer peripheral edge on the second surface 2b side of the first wafer 2 is processed (chamfered) so that the thickness gradually decreases toward the radially outward direction of the first wafer 2. Therefore, the influence of surface tension acting on the liquid resin 78 is reduced. Accordingly, according to this embodiment, a uniform resin layer 80 can be formed on the ground surface (second surface 2b) of the first wafer 2 after grinding.

[0043] If a resist film is formed as the resin layer 80, exposure is performed using an appropriate photomask, followed by development and etching in sequence, after which the resin layer 80 as a resist film is removed from the second surface 2b of the first wafer 2.

[0044] [Splitting Steps] After performing the resin layer formation step, the first wafer 2 and the second wafer 26 are separated along the planned separation line 4 of the first wafer 2, and a separation step is performed to manufacture a device chip.

[0045] The splitting step can be performed, for example, using the cutting device 12 described above. However, the thickness of the cutting blade 24 should be smaller than the width of the planned splitting line 4. Although the splitting step is not shown in the diagram, when performing the corner processing step using the cutting device 12, first, the second surface 2b of the first wafer 2 is turned upward, and the bonded wafer 36 is held by suction on the upper surface of the chuck table 14. Next, the bonding wafer 36 is imaged with the imaging unit (not shown) of the cutting device 12, and the planned splitting line 4 of the first wafer 2 is aligned in the X-axis direction based on the image of the bonding wafer 36 captured by the imaging unit. The imaging unit has a camera (for example, an infrared camera) capable of imaging the inside of the first wafer 2 and detecting the planned splitting line 4. Next, the cutting blade 24 is positioned above the planned splitting line 4 aligned in the X-axis direction. Then, the cutting edge of the cutting blade 24, which is rotating at high speed, is made to cut into the planned splitting line 4 aligned in the X-axis direction, and cutting fluid is supplied while the chuck table 14 is fed in the X-axis direction. In this way, the bonded wafer 36 is cut along the planned division line 4.

[0046] Next, the cutting blade 24 is indexed and fed in the Y-axis direction by the distance of the division line 4 in the Y-axis direction, and the cutting of the bonded wafer 36 with the cutting blade 24 is repeated. In this way, the bonded wafer 36 is cut along all of the division line 4 aligned in the X-axis direction. Next, the chuck table 14 is rotated 90 degrees, and the cutting and indexing of the bonded wafer 36 are repeated alternately. In this way, the bonded wafer 36 is cut along all of the division line 4 that are orthogonal to the division line 4 that was cut earlier. In this manner, the bonded wafer 36 is divided along the division line 4 of the first wafer 2, and a device chip is manufactured.

[0047] The splitting step can also be performed using a laser processing device. When performing the splitting step using a laser processing device, the focal point of a laser beam with a wavelength that absorbs the bonded wafer 36 is positioned on the upper surface of the bonded wafer 36, and the laser beam is irradiated along the planned splitting line 4 of the first wafer 2 to perform ablation processing, thereby splitting the bonded wafer 36 along the planned splitting line 4. Alternatively, the focal point of a laser beam with a wavelength that transmits the bonded wafer 36 is positioned inside the bonded wafer 36, and the laser beam is irradiated along the planned splitting line 4 of the first wafer 2 to form a modified layer inside the bonded wafer 36 along the planned splitting line 4, and then the bonded wafer 36 is split by applying an external force to the bonded wafer 36.

[0048] [First variation] The present invention is not limited to the embodiments described above and is capable of various modifications. In the embodiments described above, an example was given in which the joining step is performed after the chamfer removal step, but conversely, the joining step may be performed before the chamfer removal step. That is, as shown in Figures 10(a) and 10(b), after joining the first wafer 2 and the second wafer 26, which do not have the chamfer 8 removed, the entire chamfer 8 of the first wafer 2 may be removed using the cutting device 12, as shown in Figure 10(c). In this case, the chamfer 8 is removed completely from the second surface 2b side to the first surface 2a side.

[0049] [Second variation] In the embodiment described above, the outer edge of the first wafer 2 after the chamfer removal step was perpendicular to the first surface 2a and the second surface 2b, but it does not have to be perpendicular to the first surface 2a and the second surface 2b. For example, if the chamfer removal step is performed using a cutting blade 24 in which the first side surface 24b is inclined with respect to the outer edge 24a (see Figure 11(a)), or a cutting blade 24 in which both the first side surface 24b and the second side surface 24c are inclined with respect to the outer edge 24a (see Figure 11(b)), the outer edge of the first wafer 2 will be inclined with respect to the first surface 2a and the second surface 2b, as shown in Figure 11(c). After the chamfer removal step is performed, the bonding step and the grinding step are performed in order, as shown in Figure 11(d). In Figure 11(d), the portion ground in the grinding step is shown by a dashed line. Next, as shown in Figure 11(e), a corner processing step is performed to form inclined surfaces (two-stage inclined surfaces) with different angles relative to the first surface 2a and the second surface 2b on the outer edge of the first wafer 2. Then, as shown in Figure 11(f), when the resin layer formation step is performed, the effect of surface tension acting on the liquid resin 78 is further reduced by the two-stage inclined surfaces. Therefore, the uniformity of the thickness of the resin layer 80 can be further improved. Although Figure 11(f) shows two-stage inclined surfaces, three-stage inclined surfaces may also be used. Furthermore, in the second modified example, R-chamfering may also be performed in the corner processing step.

[0050] [Third variation] Furthermore, as shown in Figures 12(a) and 12(b), when the chamfer removal step is performed after the bonding step, if the chamfer removal step is performed with the axis Y1 of the cutting blade 24 separated from the center C of the first wafer 2 in the X-axis direction, the outer edge of the first wafer 2 becomes a curved surface, as shown in Figure 12(c). In this case as well, when the grinding step, corner processing step and resin layer formation step are performed (see Figures 12(d) to 12(f)), the effect of surface tension acting on the liquid resin 78 is further reduced by the curved and inclined surfaces. Therefore, the uniformity of the thickness of the resin layer 80 can be further improved. In addition, R chamfering may be performed in the corner processing step to make the outer edge of the first wafer 2 a two-stage curved surface. Also, in Figure 12(c), processing is performed only on the first wafer 2 in the chamfer removal step, but the cutting blade 24 may be made to cut all the way to the second wafer 26.

[0051] [Fourth variation] Regarding the chamfer removal step, although a cutting device 12 is used in the above embodiment, a laser processing device 82 shown in Figures 13(a) and 13(b) may also be used. The laser processing device 82 includes a chuck table 84 for holding the workpiece and a laser irradiation unit 86 for irradiating the workpiece held in the chuck table 84 with a laser beam LB.

[0052] (Chuck table 84 of laser processing machine 82) A disc-shaped suction chuck 88 is positioned at the upper end of the chuck table 84. The suction chuck 88 is made of a porous material such as porous ceramics and is connected to a suction pump (not shown). The chuck table 84 generates a suction force on the upper surface of the suction chuck 88 using the suction pump, and holds the workpiece placed on the upper surface of the chuck table 84 by suction. The chuck table 84 is also rotatable about an axis Z7 that extends in the Z-axis direction through the center of the suction chuck 88.

[0053] (Laser irradiation unit 86 of laser processing device 82) The laser irradiation unit 86 includes an oscillator (not shown) that emits a laser beam LB with a wavelength that is penetrating to the first wafer 2, and a focuser 90 that focuses the laser beam LB emitted by the oscillator.

[0054] The chamfer removal step using the laser processing device 82 may be performed before or after the bonding step. When the chamfer removal step is performed using the laser processing device 82 before the bonding step, first, the first wafer 2 is held by suction on the upper surface of the chuck table 84 with the first surface 2a facing upwards. At this time, the center of the first wafer 2 is aligned with the axis Z7. Next, while rotating the chuck table 84 in the direction indicated by arrow R7, a laser beam LB with a wavelength that is transparent to the first wafer 2 is irradiated onto the first wafer 2 to form a ring-shaped modified layer 92 along the outer edge of the first wafer 2. Next, the focusing position of the laser beam LB is changed and the laser beam LB is irradiated onto the first wafer 2 in the same manner as above. By repeating the change in focusing position and irradiation with the laser beam LB in this manner, multiple ring-shaped modified layers 92 are formed as shown in Figure 13(a), and the overall shape of the modified layer 92 is made L-shaped in cross-section. When the chamfer removal step is performed using the laser processing device 82 after the bonding step, multiple ring-shaped modified layers 92 are formed by repeatedly changing the focusing position and irradiating with the laser beam LB, as shown in Figure 13(b), and the overall shape of the modified layer 92 is made into an I-shaped cross-section extending in the vertical direction. Subsequently, when the grinding step is performed, at least a portion of the chamfer 8 of the first wafer 2 is removed in an annular shape along the outer circumference of the first wafer 2 along the modified layer 92.

[0055] As described above, in this embodiment, the corner portion 2c of the outer peripheral edge on the second surface 2b side of the first wafer 2 is processed (chamfered) so that the thickness gradually decreases toward the radially outward direction, thereby reducing the influence of surface tension acting on the liquid resin 78. Therefore, according to this embodiment, a uniform resin layer 80 can be formed on the ground surface (second surface 2b) of the first wafer 2 after grinding. [Explanation of Symbols]

[0056] 2: First wafer 2a: 1st page 2b: 2nd side 2c: Corner 4: Planned division lines 6: Devices 8: Chamfered section 24: Cutting blade 26: Second wafer 26a: 1st page 26b: 2nd side 28: Planned division line 30: Devices 32: Chamfered section 50: Grinding Wheel 52: Grinding Wheel 66: Polishing pad 78: Liquid resin 80: Resin layer

Claims

1. A wafer processing method for processing a first wafer having a first surface and a second surface opposite to the first surface, and having a chamfered portion formed on its outer peripheral edge, A chamfer removal step of removing at least a portion of the chamfered portion of the first wafer in an annular shape along the outer circumference of the first wafer, A bonding step of bonding the first surface of the first wafer to the second wafer, A grinding step is performed after the chamfer removal step and the bonding step, in which the second surface of the first wafer is ground with a grinding wheel equipped with annularly arranged grinding wheels, A corner processing step is performed on the corner of the outer edge of the second surface side of the first wafer that was ground in the grinding step, such that the thickness gradually decreases toward the radially outward direction. A wafer processing method comprising: a resin layer forming step, after the corner processing step, a step of forming a resin layer by applying a liquid resin to the second surface of the first wafer.

2. The wafer processing method according to claim 1, wherein the bonding step is performed after the chamfer removal step.

3. The wafer processing method according to claim 1, wherein the bonding step is performed before the chamfer removal step.

4. A wafer processing method according to any one of claims 1 to 3, wherein in the corner processing step, the corner is processed with the grinding wheel by moving the grinding wheel and the first wafer relatively.

5. A wafer processing method according to any one of claims 1 to 3, wherein in the corner processing step, the corner is processed with the cutting blade by moving the annular cutting blade having a cutting edge on its outer circumference relatively with the first wafer.

6. A wafer processing method according to any one of claims 1 to 3, wherein in the corner processing step, the second surface of the first wafer is polished and the corner is processed with a polishing pad.

7. A method for manufacturing chips, A chamfer removal step of a first wafer having a first surface on which devices are formed in each of a plurality of regions demarcated by a plurality of division lines, and a second surface opposite to the first surface, and having a chamfer formed at its outer edge, wherein at least a portion of the chamfer is removed in an annular manner along the outer circumference of the first wafer, A bonding step of bonding the first surface of the first wafer to the second wafer, A grinding step is performed after the chamfer removal step and the bonding step, in which the second surface of the first wafer is ground with a grinding wheel equipped with annularly arranged grinding wheels, A corner processing step is performed on the corner of the outer edge of the second surface side of the first wafer that was ground in the grinding step, such that the thickness gradually decreases toward the radially outward direction. A resin layer forming step is performed after the corner processing step, by applying a liquid resin to the second surface of the first wafer to form a resin layer. A method for manufacturing a device chip, comprising: a resin layer formation step, followed by a division step of dividing the first wafer and the second wafer along the planned division line of the first wafer to manufacture a device chip.

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