Wafer processing method

Abstract

To provide a wafer processing method that keeps processing variation of a wafer within an allowable range.SOLUTION: A wafer processing method includes: a first laying step in which a UV ray curable resin 12 is laid on a glass substrate 10; a first laminate formation step in which a wafer 2 is opposed and pressed against the UV ray curable resin 12 and UV rays are radiated from an underside of the glass substrate 10, in order to solidify the UV ray curable resin 12 and form a first laminate 18; a sheet laying step for laying a transparent sheet 20 on a transparent glass table; a second laying step in which UV ray curable resin 22 is laid on the sheet 20; a second laminate formation step in which a side of the glass substrate 10 of the first laminate 18 is opposed and pressed against the UV ray curable resin 22 and UV rays are radiated from the underside of the glass table, in order to solidify the UV ray curable resin 22 and form a second laminate 24; a holding step for making a chuck table of a processing device hold a side of the sheet 20 of the second laminate 24; and a processing step for subjecting the wafer 2 to processing with the processing device.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] A wafer has a number of devices such as ICs and LSIs formed on its surface, separated by planned dividing lines. The back surface is ground by a grinding machine to form the wafer into the desired thickness, and the wafer is then divided into individual device chips by a dicing machine. Each of the divided device chips is used in electrical equipment such as mobile phones and personal computers.

[0003] In addition, TF-SAW devices, which excite surface acoustic waves using a thin piezoelectric film, which is indispensable for communication devices such as mobile phones, or a regular comb-shaped electrode formed on a substrate, are made by bonding an LT (LiTaO3: lithium tantalate) wafer or an LN (LiNbO3: lithium niobate) wafer to the top surface of a glass substrate, and then thinning the wafer to, for example, about 5 μm and mounting the wafer in the communication device as an individual SAW device chip.

[0004] A processing apparatus for processing a wafer bonded to a glass substrate includes a chuck table capable of suction-holding and rotating the glass substrate, and a processing means, and is capable of performing desired processing on the wafer bonded to the glass substrate (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-137909 Summary of the Invention [Problem to be solved by the invention]

[0006] However, after processing the wafer, there are cases where the processing accuracy varies, and in such cases, there is a problem that the quality of the device chips is not stable.

[0007] An object of the present invention is to provide a wafer processing method capable of keeping the processing variation of the wafer within an allowable range. [Means for solving the problem]

[0008] According to the present invention, there is provided the following wafer processing method that solves the above problems. "A wafer processing method comprising the steps of: a first laying step of laying an ultraviolet curing resin on an upper surface of a glass substrate; a first laminate formation step of pressing the bottom surface of the wafer against the ultraviolet curing resin laid on the top surface of the glass substrate to form a first laminate by irradiating ultraviolet rays from the bottom surface of the glass substrate to solidify the ultraviolet curing resin sandwiched between the glass substrate and the wafer; a sheet placement step of placing a transparent sheet on an upper surface of the transparent glass table; a second laying step of laying an ultraviolet curable resin on the upper surface of the sheet; a second laminate formation process in which the glass substrate side of the first laminate is faced to the ultraviolet curing resin laid on the upper surface of the sheet, and pressed together to form a single laminate, and ultraviolet light is irradiated from the underside of the glass table to solidify the ultraviolet curing resin sandwiched between the glass substrate and the sheet, thereby forming a second laminate; a holding step of holding the sheet side of the second laminate on a holding surface of a chuck table of a processing device; and a processing step of processing the wafer by the processing apparatus.

[0009] According to the present invention, there is also provided the following wafer processing method which solves the above problems. "A wafer processing method comprising the steps of: a first laying step of laying an ultraviolet curing resin on an upper surface of a glass substrate; a first laminate formation step of pressing the bottom surface of the wafer against the ultraviolet curing resin laid on the top surface of the glass substrate to form a first laminate by irradiating ultraviolet rays from the bottom surface of the glass substrate to solidify the ultraviolet curing resin sandwiched between the glass substrate and the wafer; an adhesive sheet disposing step of disposing an adhesive sheet having an adhesive layer on an upper surface of a transparent glass table such that the surface opposite to the adhesive layer is in contact with the glass table; a second laminate formation step of pressing the glass substrate side of the first laminate against the adhesive layer of the adhesive sheet to form a second laminate; a holding step of holding the adhesive sheet side of the second laminate on a holding surface of a chuck table of a processing device; and a processing step of processing the wafer by the processing device.

[0010] The glass substrate may have both a non-flat upper surface and a non-flat lower surface. Preferably, in the first laying step, the lower surface of the glass substrate is placed on the upper surface of the glass table, and in the first laminate forming step, ultraviolet light is irradiated from the lower surface of the glass table. The processing device may be a grinding device having a grinding wheel rotatably mounted thereon, the grinding wheels being arranged in an annular shape. The processing device may be a cutting device having a cutting blade rotatably mounted thereon. Effect of the Invention

[0011] The wafer processing method of the present invention includes the steps of: a first laying step of laying an ultraviolet curing resin on an upper surface of a glass substrate; a first laminate formation step of pressing the bottom surface of the wafer against the ultraviolet curing resin laid on the top surface of the glass substrate to form a first laminate by irradiating ultraviolet rays from the bottom surface of the glass substrate to solidify the ultraviolet curing resin sandwiched between the glass substrate and the wafer; a sheet placement step of placing a transparent sheet on an upper surface of the transparent glass table; a second laying step of laying an ultraviolet curable resin on the upper surface of the sheet; a second laminate formation process in which the glass substrate side of the first laminate is faced to the ultraviolet curing resin laid on the upper surface of the sheet, and pressed together to form a single laminate, and ultraviolet light is irradiated from the underside of the glass table to solidify the ultraviolet curing resin sandwiched between the glass substrate and the sheet, thereby forming a second laminate; a holding step of holding the sheet side of the second laminate on a holding surface of a chuck table of a processing device; Since the method includes a processing step of processing the wafer by the processing device, even if the glass substrate has irregularities or distortion, processing variations of the wafer can be kept within an allowable range.

[0012] Further, the wafer processing method of the present invention includes the steps of: a first laying step of laying an ultraviolet curing resin on an upper surface of a glass substrate; a first laminate formation step of pressing the bottom surface of the wafer against the ultraviolet curing resin laid on the top surface of the glass substrate to form a first laminate by irradiating ultraviolet rays from the bottom surface of the glass substrate to solidify the ultraviolet curing resin sandwiched between the glass substrate and the wafer; an adhesive sheet disposing step of disposing an adhesive sheet having an adhesive layer on an upper surface of a transparent glass table such that the surface opposite to the adhesive layer is in contact with the glass table; a second laminate formation step of pressing the glass substrate side of the first laminate against the adhesive layer of the adhesive sheet to form a second laminate; a holding step of holding the adhesive sheet side of the second laminate on a holding surface of a chuck table of a processing device; Since the method includes a processing step of processing the wafer by the processing device, even if the glass substrate has irregularities or distortion, processing variations of the wafer can be kept within an allowable range. [Brief description of the drawings]

[0013] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3](a) A schematic diagram showing the state in which the underside of the wafer faces an ultraviolet-curable resin laid on the upper surface of a glass substrate, (b) a schematic diagram showing the state in which the wafer is pressed against the glass substrate, and (c) a perspective view showing the first laminate. [Figure 4] FIG. 1A is a perspective view showing a sheet disposing step, and FIG. [Diagram 5] FIG. [Figure 6] FIG. 2A is a schematic diagram showing a state in which the glass substrate side of the first laminate is placed on the upper surface of a glass table, and FIG. 2B is a schematic diagram showing a state in which the first laminate is pressed against a sheet. [Figure 7] FIG. 2A is a perspective view of a second laminate; FIG. 2B is a cross-sectional view of the second laminate shown in FIG. [Figure 8] FIG. 2A is a perspective view of a second laminate having an adhesive sheet, and FIG. 2B is a cross-sectional view of the second laminate shown in FIG. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] FIG. [Figure 12] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, preferred embodiments of the wafer processing method according to the present invention will be described with reference to the drawings.

[0015] (Wafer 2) 1 shows a disk-shaped wafer 2 that can be ground by the method according to the present invention. Examples of the material of the wafer 2 include LT (LiTaO3: lithium tantalate) and LN (LiNbO3: lithium niobate). The surface 2a of the wafer 2 is partitioned into a plurality of rectangular regions by lattice-shaped division lines 4, and devices 6 such as SAW devices are formed in the plurality of rectangular regions. In addition, a notch 8 indicating a crystal orientation is provided on the periphery of the wafer 2. The thickness of the wafer 2 before grinding is, for example, about 300 μm.

[0016] (First installation process) In this embodiment, first, a first laying step is carried out in which an ultraviolet curing resin 12 is laid on the upper surface of a glass substrate 10 as shown in FIG.

[0017] The glass substrate 10 used in this process is a substrate for supporting the wafer 2. The glass substrate 10 is preferably transparent. However, the glass substrate 10 may have both non-flat upper and lower surfaces. For example, the glass substrate 10 may be frosted glass with unevenness formed on the upper and lower surfaces. The diameter of the glass substrate 10 may be the same as that of the wafer 2, or may be larger than that of the wafer 2. The ultraviolet curing resin 12 laid on the glass substrate 10 in this process is not yet irradiated with ultraviolet rays (i.e., not yet cured) and is in a fluid state. In the illustrated embodiment, the ultraviolet curing resin 12 is laid on the glass substrate 10 with the lower surface of the glass substrate 10 placed on the upper surface of the glass table 14, but the table on which the glass substrate 10 is placed may be any table that transmits ultraviolet rays, and may be, for example, an acrylic plate table.

[0018] (First laminate formation process) After the first laying step is performed, the underside of the wafer 2 is brought face to face with the ultraviolet-curable resin 12 laid on the upper surface of the glass substrate 10 and pressed against it to form one body, and then a first laminate formation step is performed in which ultraviolet light is irradiated from the underside of the glass substrate 10 to solidify the ultraviolet-curable resin 12 sandwiched between the glass substrate 10 and the wafer 2, thereby forming a first laminate.

[0019] In the first laminate formation step, as shown in FIG. 3(a), first, the front surface 2a of the wafer 2 is placed against the ultraviolet curing resin 12 laid on the upper surface of the glass substrate 10, and the wafer 2 is placed on the glass substrate 10. Next, as shown in FIG. 3(b), the upper surface (back surface 2b) of the wafer 2 is pressed against the glass substrate 10 by a pressing means 16 having a lower surface parallel to the upper surface of the glass table 14, and the glass substrate 10 and the wafer 2 are integrated. At this time, the ultraviolet curing resin 12 is evenly spread between the lower surface (front surface 2a) of the wafer 2 and the upper surface of the glass substrate 10. Next, ultraviolet rays UV are irradiated from the lower surface of the glass substrate 10 (the lower surface of the glass table 14 in this embodiment) to solidify the ultraviolet curing resin 12 sandwiched between the glass substrate 10 and the wafer 2. In this way, as shown in FIG. 3(c), a first laminate 18 is formed in which the wafer 2 and the glass substrate 10 are integrated by the ultraviolet curing resin 12.

[0020] (Sheet installation process) After the first laminate formation step is performed, a sheet disposing step is performed in which a transparent sheet 20 is disposed on the upper surface of a transparent glass table 14, as shown in FIG. 4(a).

[0021] The glass table 14 used in the sheet disposing step may be the same as the glass table 14 used in the first laying step and the first laminate forming step. The sheet 20 may be made of an appropriate synthetic resin such as PET resin. The sheet 20 is circular, the diameter of the sheet 20 is the same as the diameter of the wafer 2, and the thickness is about 10 to 50 μm.

[0022] Alternatively, instead of the sheet disposing step, as shown in Fig. 4(b), an adhesive sheet disposing step may be performed in which an adhesive sheet 21 having an adhesive layer on the upper surface of a transparent glass table 14 is disposed so that the surface opposite to the adhesive layer is in contact with the glass table 14. The adhesive sheet 21 has an adhesive layer on one side 21a and no adhesive layer on the other side 21b. In the adhesive sheet disposing step, the adhesive sheet 21 is disposed on the upper surface of the transparent glass table 14 with the one side 21a on which the adhesive layer is provided facing upward and the other side 21b on which the adhesive layer is not provided facing downward.

[0023] (Second laying process) When the sheet disposing step is performed, a second laying step is performed in which an ultraviolet curing resin 22 is laid on the upper surface of the sheet 20, as shown in Fig. 5. The ultraviolet curing resin 22 laid in the second laying step is in a fluid state, not yet irradiated with ultraviolet rays, like the ultraviolet curing resin 12 laid in the first laying step. Note that when the adhesive sheet disposing step is performed instead of the sheet disposing step, the second laying step does not need to be performed.

[0024] (Second laminate formation process) When the second laying process is performed, after the second laying process is performed, the glass substrate 10 side of the first laminate 18 is faced to the ultraviolet curing resin 22 laid on the upper surface of the sheet 20, pressed together to form one body, and ultraviolet rays UV are irradiated from the underside of the glass table 14 to solidify the ultraviolet curing resin 22 sandwiched between the glass substrate 10 and the sheet 20, thereby forming a second laminate.

[0025] In the second laminate formation process, as shown in FIG. 6(a), first, the glass substrate 10 side of the first laminate 18 is placed against the ultraviolet curing resin 22 laid on the upper surface of the sheet 20, and the first laminate 18 is placed on the sheet 20 on the glass table 14. Next, as shown in FIG. 6(b), the upper surface of the first laminate 18 (the upper surface of the wafer 2) is pressed against the sheet 20 by the pressing means 16 to integrate the first laminate 18 and the sheet 20. At this time, the ultraviolet curing resin 22 is evenly spread between the lower surface of the glass substrate 10 and the upper surface of the sheet 20. Next, ultraviolet rays UV are irradiated from the lower surface of the glass table 14 to solidify the ultraviolet curing resin 22 sandwiched between the glass substrate 10 and the sheet 20. In this way, as shown in FIG. 7(a) and FIG. 7(b), a second laminate 24 is formed in which the first laminate 18 and the sheet 20 are integrated by the ultraviolet curing resin 22.

[0026] In the second laminate 24 thus formed, even if the lower surface of the glass substrate 10 is uneven or distorted, the unevenness and distortedness of the glass substrate 10 are absorbed by the ultraviolet curing resin 22 sandwiched between the sheet 20 and the glass substrate 10. Therefore, the lower surface of the second laminate 24 is flattened. As a result, the upper surface of the wafer 2 (the rear surface 2b in the illustrated embodiment) and the lower surface of the sheet 20 become parallel with high precision.

[0027] In addition, when the adhesive sheet disposing step is performed, the second laminate forming step is performed after the adhesive sheet disposing step. In this case, in the second laminate forming step, as shown in FIG. 8(a) and FIG. 8(b), the glass substrate 10 side of the first laminate 18 is made to face the adhesive layer provided on one side 21a of the adhesive sheet 21. Then, the adhesive sheet 21 and the first laminate 18 are pressed together to form a second laminate 24'. In the second laminate 24', the unevenness and distortion of the glass substrate 10 are absorbed by the adhesive layer of the adhesive sheet 21. Therefore, the lower surface of the second laminate 24' is flattened. As a result, the upper surface of the wafer 2 (the back surface 2b in the illustrated embodiment) and the lower surface of the adhesive sheet 21 become parallel with high accuracy.

[0028] (holding process) After the second laminate forming step is performed, a holding step is performed in which the sheet 20 side of the second laminate 24 or the adhesive sheet 21 side of the second laminate 24' is held on a holding surface of a chuck table of a processing device. In the holding step, for example, a grinding device 26 shown in FIG. 9 can be used.

[0029] (Grinding equipment 26) The grinding device 26 includes a rotatable chuck table 28 that holds the workpiece by suction, a grinding means 30 having a grinding wheel with grinding stones arranged in a ring shape rotatably mounted thereon, and a feeding means 32 that feeds the grinding means 30 for grinding.

[0030] (Chuck table 28) A circular suction chuck 34 is disposed on the upper end of the chuck table 28. The suction chuck 34 is formed from a porous material such as porous ceramics. The suction chuck 34 is connected to a suction means (not shown). In the chuck table 28, the suction means generates a suction force on the upper surface of the suction chuck 34, and the workpiece placed on the upper surface of the suction chuck 34 is sucked and held. In this manner, the upper surface of the suction chuck 34 serves as the holding surface of the chuck table 28.

[0031] The chuck table 28 is rotated around an axis in the vertical direction by a motor (not shown). Furthermore, the chuck table 28 is adapted to be moved in the X-axis direction by an X-axis moving means (not shown) between a workpiece mounting / removal position (position shown in FIG. 9) and a grinding position (position shown in FIG. 10) below the grinding means 30. The X-axis direction is the direction indicated by the arrow X in FIG. 9.

[0032] (Grinding means 30) The grinding means 30 includes a lifting plate 38 supported on a support wall 36 provided at an end (the rear end in Figure 9) of the grinding device 26 so as to be freely raised and lowered, a protruding member 40 protruding from the lifting plate 38, a spindle 42 supported on the protruding member 40 so as to be rotatable about an axis extending in the vertical direction, and a spindle motor 44 that rotates the spindle 42.

[0033] Continuing the explanation with reference to Figure 10, a disk-shaped wheel mount 46 is fixed to the lower end of the spindle 42, and an annular grinding wheel 50 is fastened to the underside of the wheel mount 46 by bolts 48. A plurality of grinding stones 52 are fixed to the outer circumferential edge of the underside of the grinding wheel 50, and are arranged annularly at intervals in the circumferential direction.

[0034] (Feeding means 32) 9, the feeding means 32 has a ball screw 54 extending in the vertical direction along one surface of the support wall 36, and a motor 56 that rotates the ball screw 54. A nut portion (not shown) of the ball screw 54 is connected to the lift plate 38. The feeding means 32 converts the rotational motion of the motor 56 into linear motion by the ball screw 54 and transmits it to the lift plate 38, and feeds the grinding means 30 in the vertical direction for grinding along a guide rail 36a attached to one surface of the support wall 36.

[0035] In the holding step, first, the X-axis moving means is operated to position the chuck table 28 at the attachment / detachment position shown in FIG. 9. Next, the sheet 20 side of the second laminate 24 or the adhesive sheet 21 side of the second laminate 24' is placed on the upper surface of the chuck table 28 with the sheet 20 side of the second laminate 24 or the adhesive sheet 21 side of the second laminate 24' facing down (with the back surface 2b of the wafer 2 facing up). Then, the suction means is operated to generate a suction force on the upper surface of the suction chuck 34. In this way, the sheet 20 side of the second laminate 24 or the adhesive sheet 21 side of the second laminate 24' is suction-held on the holding surface of the chuck table 28. As described above, since the lower surface (sheet 20 side) of the second laminate 24 is flattened by the ultraviolet curing resin 22, when the second laminate 24 is held on the chuck table 28, the lower surface of the second laminate 24 is in close contact with the chuck table 28. On the other hand, in the case of the second laminate 24', the lower surface (the adhesive sheet 21 side) of the second laminate 24' is flattened by the adhesive layer of the adhesive sheet 21, so that when the second laminate 24' is held on the chuck table 28, the lower surface of the second laminate 24' adheres to the chuck table 28.

[0036] (Processing process) After the holding step is performed, a processing step is performed in which the wafer 2 is processed by a processing device. Here, as the processing step, a grinding step in which the upper surface of the wafer 2 is ground by the grinding means 30 of the grinding device 26 to thin the wafer 2 to a desired thickness will be described.

[0037] In the grinding process, first, the X-axis moving means is operated to position the chuck table 28 at the grinding position shown in FIG. 10. Next, the spindle 42 is rotated in the R1 direction at a predetermined rotation speed (for example, 6000 rpm). Also, the chuck table 28 is rotated in the R2 direction at a predetermined rotation speed (for example, 300 rpm). Next, the spindle 42 is lowered by the feed means 32 to bring the grinding wheel 52 into contact with the back surface 2b of the wafer 2, and grinding water is supplied to the portion where the grinding wheel 52 is in contact with the back surface 2b. Then, the spindle 42 is lowered at a predetermined grinding feed speed (for example, 1.0 μm / s), thereby grinding the back surface 2b of the wafer 2 with the grinding wheel 52. In this manner, the wafer 2 is thinned to a desired thickness (for example, about 5 μm). In this embodiment, as described above, the upper surface of the wafer 2 and the lower surface of the sheet 20 (or the adhesive sheet 21) are parallel to each other with high accuracy, so that the thickness of the wafer 2 after thinning is uniform.

[0038] In the above description, an example has been described in which the holding step and the processing step are performed using the grinding device 26, but the holding step and the processing step may also be performed using a cutting device 58 shown in FIG.

[0039] (Cutting device 58) The cutting device 58 includes a rotatable chuck table 60 that holds the workpiece by suction, cutting means 62 to which a cutting blade is rotatably attached, and a feed means 64 that moves the chuck table 60 and the cutting means 62 relative to one another.

[0040] (Chuck table 60) A circular suction chuck 66 is disposed on the upper end of the chuck table 60. The suction chuck 66 is formed from a porous material such as porous ceramics. The suction chuck 66 is connected to a suction means (not shown). In the chuck table 60, the suction means generates a suction force on the upper surface of the suction chuck 66, and the workpiece placed on the upper surface of the suction chuck 66 is sucked and held. In this manner, the upper surface of the suction chuck 66 serves as the holding surface of the chuck table 60.

[0041] The chuck table 60 is fixed to the upper surface of the X-axis movable plate 70 via support columns 68. The X-axis movable plate 70 is supported by a base 72 so as to be movable in the X-axis direction indicated by the arrow X in Fig. 11. The chuck table 60 is rotated around an axis extending in the vertical direction by a motor (not shown). The Y-axis direction indicated by the arrow Y in Fig. 11 is a direction perpendicular to the X-axis direction, and the Z-axis direction indicated by the arrow Z in Fig. 11 is a vertical direction perpendicular to the X-axis and Y-axis directions. The XY plane defined by the X-axis and Y-axis directions is substantially horizontal.

[0042] (Cutting means 62) The cutting means 62 includes a gate-shaped support member 74, a Y-axis movable member 76 supported by the support member 74 so as to be movable in the Y-axis direction, and a Z-axis movable member 78 supported by the Y-axis movable member 76 so as to be movable in the Z-axis direction. A spindle housing 80 is fixed to the lower end of the Z-axis movable member 78. Referring to FIG. 12, a spindle 82 is supported in the spindle housing 80 so as to be rotatable about the Y-axis direction. A spindle motor (not shown) for rotating the spindle 82 is provided at one end of the spindle 82. An annular cutting blade 84 is fixed to the other end of the spindle 82.

[0043] (Feeding means 64) Explaining with reference to FIG. 11, the feed means 64 includes an X-axis feed means 86 which feeds the chuck table 60 in the X-axis direction for processing, a Y-axis feed means 88 which indexes and feeds the cutting blade 84 in the Y-axis direction, and a Z-axis feed means 90 which cuts and feeds the cutting blade 84 in the Z-axis direction.

[0044] (X-axis feed means 86) The X-axis feed means 86 has a ball screw 92 connected to the X-axis movable plate 70 and extending in the X-axis direction, and a motor 94 that rotates the ball screw 92. The X-axis feed means 86 converts the rotational motion of the motor 94 into linear motion using the ball screw 92 and transmits it to the X-axis movable plate 70, moving the X-axis movable plate 70 in the X-axis direction along the pair of X-axis guide rails 72a of the base 72. As a result, the chuck table 60 is fed for processing in the X-axis direction.

[0045] (Y-axis feed means 88) The Y-axis feed means 88 has a ball screw 96 connected to the Y-axis movable member 76 and extending in the Y-axis direction, and a motor 98 that rotates the ball screw 96. The Y-axis feed means 88 converts the rotational motion of the motor 98 into linear motion using the ball screw 96 and transmits it to the Y-axis movable member 76, moving the Y-axis movable member 76 in the Y-axis direction along a pair of Y-axis guide rails 74a attached to the support member 74. As a result, the cutting blade 84 is indexed and fed in the Y-axis direction.

[0046] (Z-axis feed means 90) The Z-axis feed means 90 has a ball screw 100 connected to the Z-axis movable member 78 and extending in the Z-axis direction, and a motor 102 that rotates the ball screw 100. The Z-axis feed means 90 converts the rotational motion of the motor 102 into linear motion using the ball screw 100 and transmits it to the Z-axis movable member 78, and moves the Z-axis movable member 78 in the Z-axis direction along a pair of Z-axis guide rails 76a attached to the Y-axis movable member 76. This causes the cutting blade 84 to cut and be fed in the Z-axis direction.

[0047] (Holding step using cutting device 58) In the holding step using the cutting device 58, first, the sheet 20 side of the second laminate 24 or the adhesive sheet 21 side of the second laminate 24' is placed on the upper surface of the chuck table 60 with the sheet 20 side of the second laminate 24 or the adhesive sheet 21 side of the second laminate 24' facing down (with the back surface 2b of the wafer 2 facing up). Then, the suction means is operated to generate a suction force on the upper surface of the suction chuck 66. In this way, the sheet 20 side of the second laminate 24 or the adhesive sheet 21 side of the second laminate 24' is suction-held on the holding surface of the chuck table 60. As described above, since the lower surface (sheet 20 side) of the second laminate 24 is flattened by the ultraviolet curing resin 22, when the second laminate 24 is held on the chuck table 60, the lower surface of the second laminate 24 is in close contact with the chuck table 60. On the other hand, in the case of the second laminate 24', the lower surface (the adhesive sheet 21 side) of the second laminate 24' is flattened by the adhesive layer of the adhesive sheet 21, so that when the second laminate 24' is held on the chuck table 60, the lower surface of the second laminate 24' adheres to the chuck table 60.

[0048] (Processing step using cutting device 58) After the holding step is carried out using the cutting device 58, a cutting step is carried out as a processing step in which cutting is performed along the intended division lines 4 of the wafers 2 of the second stack 24 or 24' using the cutting blade 84 of the cutting device 58.

[0049] In the cutting process, first, the second laminate 24 or 24' is imaged from above by an imaging means (not shown) of the cutting device 58. The imaging means may include either an infrared camera or a visible light camera. Next, the division line 4 is aligned in the X-axis direction based on the image of the second laminate 24 or 24' imaged by the imaging means. Next, the cutting edge of the cutting blade 84 rotated at high speed in the direction indicated by the arrow R1 in FIG. 12 is cut into the division line 4 aligned in the X-axis direction to a predetermined depth from the back surface 2b, and the chuck table 60 is processed and fed in the X-axis direction while supplying cutting water to the part where the cutting edge of the cutting blade 84 is to be cut. This allows a cut groove 104 of a predetermined depth to be formed along the division line 4.

[0050] Next, the cutting blade 84 is indexed in the Y-axis direction by the interval of the division lines 4 in the Y-axis direction. Then, the formation of the cut grooves 104 and the indexing are alternately repeated to form the cut grooves 104 along all of the division lines 4 aligned in the X-axis direction. In addition, the chuck table 60 is rotated 90 degrees, and the formation of the cut grooves 104 and the indexing are alternately repeated. As a result, the cut grooves 104 are formed along all of the division lines 4 that are perpendicular to the division lines 4 on which the cut grooves 104 have been formed. In this way, the cut grooves 104 are formed in a lattice shape on the wafer 2 along the lattice-shaped division lines 4. In this embodiment, as described above, the upper surface of the wafer 2 and the lower surface of the sheet 20 (or the adhesive sheet 21) are parallel to each other with high accuracy, so that the variation of the cut grooves 104 can be kept within an allowable range.

[0051] As described above, in the illustrated embodiment, even if the lower surface of the glass substrate 10 has unevenness or distortion, the ultraviolet curing resin 22 sandwiched between the sheet 20 and the glass substrate 10 absorbs the unevenness or distortion of the glass substrate 10, making it possible to flatten the lower surface of the second laminate 24. Alternatively, the adhesive layer between the adhesive sheet 21 and the glass substrate 10 absorbs the unevenness or distortion of the glass substrate 10, making it possible to flatten the lower surface of the second laminate 24'. Therefore, when the second laminate 24 or 24' is held on the chuck table of the processing device, the lower surface of the second laminate 24 or 24' is in close contact with the chuck table, and the upper surface of the wafer 2 and the lower surface of the sheet 20 or the lower surface of the adhesive sheet 21 are parallel with high accuracy. As a result, even if the glass substrate 10 has unevenness or distortion, the processing variation of the wafer 2 can be kept within the allowable range.

[0052] Furthermore, even if the glass substrate 10 is frosted glass with unevenness formed on its upper and lower surfaces (even if the glass substrate 10 is opaque by itself), in this embodiment, the unevenness on the upper and lower surfaces of the glass substrate 10 is absorbed by the ultraviolet curing resins 12, 22, or the unevenness on the upper and lower surfaces of the glass substrate 10 is absorbed by the ultraviolet curing resin 12 and the adhesive layer of the adhesive sheet 21, so that the glass substrate 10 becomes transparent. As a result, it becomes possible to observe the wafer 2 through the glass substrate 10. [Explanation of symbols]

[0053] 2: Wafer 2a: Surface of the wafer 2b: Back side of wafer 10: Glass substrate 12: Ultraviolet curing resin 14: Glass table 16: Pressing means 18: First laminate 20:Sheet 21: Adhesive sheet 21a: Single side 21b: Other side 22: Ultraviolet curing resin 24: Second laminate 26: Grinding equipment 28: Chuck table 30: Grinding means 50: Grinding wheel 52: Grinding wheel 58: Cutting equipment 60: Chuck table 62:Cutting means

Claims

1. A wafer processing method comprising the steps of: a first laying step of laying an ultraviolet curing resin on an upper surface of a glass substrate; a first laminate formation step of pressing the bottom surface of the wafer against the ultraviolet curing resin laid on the top surface of the glass substrate to form a first laminate by irradiating ultraviolet rays from the bottom surface of the glass substrate to solidify the ultraviolet curing resin sandwiched between the glass substrate and the wafer; a sheet placement step of placing a transparent sheet on an upper surface of the transparent glass table; a second laying step of laying an ultraviolet curable resin on the upper surface of the sheet; a second laminate formation process in which the glass substrate side of the first laminate is faced to the ultraviolet curing resin laid on the upper surface of the sheet, and pressed together to form a single laminate, and ultraviolet light is irradiated from the underside of the glass table to solidify the ultraviolet curing resin sandwiched between the glass substrate and the sheet, thereby forming a second laminate; a holding step of holding the sheet side of the second laminate on a holding surface of a chuck table of a processing device; a processing step of processing a wafer by the processing device.

2. A wafer processing method comprising the steps of: a first laying step of laying an ultraviolet curing resin on an upper surface of a glass substrate; a first laminate formation step of pressing the bottom surface of the wafer against the ultraviolet curing resin laid on the top surface of the glass substrate to form a first laminate by irradiating ultraviolet rays from the bottom surface of the glass substrate to solidify the ultraviolet curing resin sandwiched between the glass substrate and the wafer; an adhesive sheet disposing step of disposing an adhesive sheet having an adhesive layer on an upper surface of a transparent glass table such that the surface opposite to the adhesive layer is in contact with the glass table; a second laminate formation step of pressing the glass substrate side of the first laminate against the adhesive layer of the adhesive sheet to form a second laminate; a holding step of holding the adhesive sheet side of the second laminate on a holding surface of a chuck table of a processing device; a processing step of processing a wafer by the processing device.

3. 3. The wafer processing method according to claim 1, wherein the glass substrate has an upper surface and a lower surface, both of which are non-flat.

4. 3. A wafer processing method as described in claim 1 or 2, wherein in the first laying step, the underside of the glass substrate is placed on the upper surface of the glass table, and in the first laminate formation step, ultraviolet light is irradiated from the underside of the glass table.

5. 3. The wafer processing method according to claim 1, wherein the processing device is a grinding device having a grinding wheel having grinding stones arranged in an annular shape rotatably mounted thereon.

6. 3. The wafer processing method according to claim 1, wherein the processing device is a cutting device having a cutting blade rotatably mounted thereon.

Images