Workpiece machining method

Abstract

To provide a workpiece machining method that makes a cutting blade less likely to be unevenly worn when an outer peripheral portion of a wafer is removed by the cutting blade.SOLUTION: A workpiece machining method applied when an outer peripheral portion of a disc-shaped workpiece having circular first and second surfaces is machined, comprises: a holding step of holding the workpiece on a side of the second surface such that the first surface of the workpiece is exposed; and a cutting step of, while rotating, after the holding step, an annular cutting blade including an annular first cutting edge portion and an annular second cutting edge portion less likely to wear than the first cutting edge portion, causing the first cutting edge portion to cut into a first region in the outer peripheral portion, then causing the second cutting edge portion to cut into a second region located outside the first region in the outer peripheral portion in a radial direction of the workpiece, and moving the cutting blade relatively along the outer peripheral portion of the workpiece, thereby cutting the outer peripheral portion of the workpiece.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for machining a workpiece. [Background technology]

[0002] In the manufacturing process of semiconductor devices, a number of streets are set in a grid pattern on the surface of a wafer, and devices such as ICs (integrated circuits) are formed in each of a number of regions partitioned by the number of streets. The back side of the wafer is ground, for example, by a grinding device or the like to thin the wafer to a predetermined thickness, and then the wafer is cut along the streets by a cutting device or the like to separate the wafer into individual regions. This results in a number of semiconductor device chips, each of which has a device.

[0003] In recent years, with the demand for higher integration of device chips, the development of stacked wafers, in which multiple wafers are stacked in three dimensions, is progressing. For example, a TSV (Through-Silicon Via) wafer, which is a type of stacked wafer, is formed by bonding multiple silicon wafers, each of which has multiple devices. Through holes (vias) are formed in each silicon wafer, and the electrodes of the devices on each silicon wafer are connected by providing through electrodes inside the vias.

[0004] In the manufacturing process of such laminated wafers, for example, one surface of a first wafer is bonded to another second wafer, and then the other surface of the first wafer is ground by a grinding device or the like to thin the first wafer to a predetermined thickness. Usually, the corners of the outer periphery of the first wafer are removed to form a rounded chamfered portion in order to increase the mechanical strength of the first wafer.

[0005] Therefore, when the first wafer is thinned by grinding, the chamfered portion (periphery) of the first wafer is processed into a thin and sharp shape (knife-edge shape). This reduces the mechanical strength of the peripheral portion of the first wafer, making the peripheral portion of the first wafer more susceptible to chipping. If this chipping reaches the device, the device will be damaged.

[0006] As a countermeasure to this problem, a technique called edge trimming is known in which the outer periphery of the wafer is cut with a cutting blade to remove the chamfered portion (see, for example, Patent Document 1). However, when the outer periphery of the wafer is processed with a cutting blade, a phenomenon occurs in which a part of the tip of the cutting blade wears out before other parts (uneven wear).

[0007] If the wafer is cut with the tip of the cutting blade being unevenly worn, the wafer may not be cut properly. Therefore, before cutting the wafer, a dressing operation is performed to shape the tip of the cutting blade flat using a dresser board (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2007-158239 A [Patent Document 2] JP 2010-000588 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, the above-mentioned dressing operation of the cutting blade increases the substantial time and cost required for the production of wafers. Therefore, a method for processing a workpiece in which the cutting blade is less likely to wear unevenly has been desired so that the dressing operation can be reduced as much as possible.

[0010] SUMMARY OF THE PRESENT DISCLOSURE ... An object of the present invention is to provide a method for processing a workpiece in which the cutting blade is less likely to wear unevenly when removing the outer periphery of a wafer with the cutting blade. [Means for solving the problem]

[0011] According to one aspect of the present invention, there is provided a method for machining a workpiece that is applied when machining an outer periphery of a disk-shaped workpiece having a first surface and a second surface that are circular, the method including: a holding step of holding the second surface side of the workpiece so that the first surface of the workpiece is exposed; and a cutting step of, after the holding step, rotating an annular cutting blade having an annular first cutting edge portion and an annular second cutting edge portion that is less susceptible to wear than the first cutting edge portion, causing the first cutting edge portion to cut into a first region within the outer periphery and the second cutting edge portion to cut into a second region within the outer periphery that is located radially outward of the first region within the outer periphery, and moving the cutting blade relatively along the outer periphery of the workpiece, thereby cutting the outer periphery of the workpiece.

[0012] Preferably, the cutting blade further comprises an annular third cutting edge portion which is more susceptible to wear than the first cutting edge portion.

[0013] Preferably, the cutting blade has a laminated structure in which the first cutting edge portion, the second cutting edge portion, and the third cutting edge portion are stacked so that the second cutting edge portion contacts the first cutting edge portion and the third cutting edge portion contacts the second cutting edge portion, and in the cutting step, the third cutting edge portion is positioned in a third region located radially outward from the outer periphery.

[0014] Preferably, the third cutting portion includes a bond but does not include an abrasive grain.

[0015] Preferably, the workpiece is a bonded wafer obtained by bonding a first wafer having a chamfered outer periphery and a second wafer together, and in the cutting step, the cutting blade is caused to cut from the first surface side of the workpiece on which the first wafer is placed to a position not reaching the second surface.

[0016] Preferably, both the first cutting edge portion and the second cutting edge portion contain abrasive grains and a binder, the grain size of the abrasive grains contained in the second cutting edge portion is larger than the grain size of the abrasive grains contained in the first cutting edge portion, the concentration of the abrasive grains contained in the second cutting edge portion is higher than the concentration of the abrasive grains contained in the first cutting edge portion, or the hardness of the binder of the abrasive grains contained in the second cutting edge portion is higher than the hardness of the binder contained in the first cutting edge portion. Effect of the Invention

[0017] In one aspect of the present invention, a cutting blade having a first cutting edge portion and a second cutting edge portion less susceptible to wear than the first cutting edge portion is used. The first cutting edge portion cuts into a first region located on the inside within the outer periphery of the workpiece, and the second cutting edge portion cuts into a second region located on the outside within the outer periphery of the workpiece.

[0018] In a cutting blade having a single cutting edge portion, the outer portion of the cutting blade that processes the outer second region is usually more likely to wear out than the inner portion of the cutting blade that processes the inner first region of the outer periphery. Therefore, by cutting the second cutting edge portion, which is relatively less likely to wear out, into this second region, the difference in the degree of wear of the first cutting edge portion and the second cutting edge portion is less likely to occur, and uneven wear of the cutting blade is suppressed. In this way, according to the method for processing a workpiece according to one aspect of the present invention, the cutting blade is less likely to wear out unevenly. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a perspective view of a workpiece. [Diagram 2] FIG. 2 is a side view of the workpiece. [Diagram 3] FIG. 3 is a perspective view of a workpiece supported by a frame via a sheet. [Figure 4] FIG. 4 is a perspective view showing a cutting device or the like as a processing device used in the method for processing a workpiece according to the embodiment. [Diagram 5]FIG. 5 is a perspective view of a cutting blade. [Figure 6] FIG. 6 is a side view of a part of the cutting edge as viewed from a direction perpendicular to the thickness direction of the cutting edge. [Figure 7] FIG. 7 is a flow diagram of a method for processing a workpiece according to an embodiment. [Figure 8] FIG. 8 is a side view showing a workpiece, a cutting blade, etc. in a cutting step of the method for processing a workpiece according to the embodiment. [Figure 9] FIG. 9 is a perspective view of the laminated wafer. [Figure 10] FIG. 10 is a side view of the laminated wafer. [Figure 11] FIG. 11 is a side view of a part of a cutting blade used in a method for processing a workpiece according to a first modified example, viewed from a direction perpendicular to the thickness direction of the cutting blade. [Figure 12] FIG. 12 is a side view showing a workpiece, a cutting blade, etc. in a cutting step of a workpiece processing method according to a first modified example. [Figure 13] FIG. 13 is a side view showing a workpiece, a cutting blade, etc. in a cutting step of a workpiece processing method according to a second modified example. [Figure 14] FIG. 14 is a side view showing a workpiece, a cutting blade, etc. in a cutting step of a workpiece processing method according to a third modified example of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. First, a workpiece used in a method for processing a workpiece according to the present embodiment will be described. Fig. 1 is a perspective view of the workpiece, and Fig. 2 is a side view of the workpiece.

[0021] 1, the workpiece 11 is, for example, a disk-shaped wafer made of a semiconductor material such as silicon. That is, the workpiece 11 is configured in a substantially disk shape having a substantially circular first surface 11a and a substantially circular second surface 11b opposite to the first surface 11a. A notch 11c is formed in a part of the outer periphery (peripheral edge) of the workpiece 11 to indicate the crystal orientation of the workpiece 11.

[0022] The diameter of the workpiece 11 (the width of the first surface 11a or the second surface 11b) is, for example, 100 mm or more and 450 mm or less, typically 300 mm. The thickness of the workpiece 11 is, for example, 100 μm or more and 10,000 μm or less, typically 775 μm. Note that the material, shape, diameter (the width of the first surface 11a or the second surface 11b) and thickness of the workpiece 11 are not limited to these. Also, the workpiece 11 may have an orientation flat instead of the notch 11c. Furthermore, the workpiece 11 may not have a notch 11c or an orientation flat.

[0023] A plurality of linear streets 13 having a predetermined width are set in a lattice pattern on the first surface 11a of the workpiece 11. The first surface 11a of the workpiece 11 is divided into a plurality of regions by the streets 13, and a device 15 such as an IC (Integrated Circuit) is provided in each of the plurality of regions.

[0024] 2, the workpiece 11 has a chamfered portion 23 formed by removing the corners of the outer periphery of the workpiece 11 to form a rounded chamfered portion 23 in an annular shape along the outer periphery of the workpiece 11. The chamfered portion 23 includes a first region 25 and a second region 27 located outside the first region 25 in the radial direction of the workpiece 11.

[0025] That is, the width of chamfered portion 23 (the length along the radial direction of workpiece 11) is expressed as the sum of the width of first region 25 and the width of second region 27. The width of chamfered portion 23 is not less than 0.5 mm and not more than 5 mm.

[0026] 3 is a perspective view of a workpiece supported by a frame via a sheet. When processing the workpiece 11, the workpiece 11 is supported by an annular frame 17 via a sheet 19 for ease of handling (transporting, holding, etc.) the workpiece 11. The frame 17 is made of a metal such as SUS (stainless steel), and a circular opening 17a is provided in the center of the frame 17, penetrating the frame 17 in the thickness direction. The diameter of the opening 17a is larger than the diameter of the workpiece 11 (the width of the first surface 11a or the second surface 11b).

[0027] A circular sheet 19 is fixed to the workpiece 11 and the frame 17. For example, the sheet 19 is a tape including a film-like base material and an adhesive layer (glue layer) provided on the base material. The base material is made of a resin such as polyolefin, polyvinyl chloride, or polyethylene terephthalate, and the adhesive layer is made of an epoxy-, acrylic-, or rubber-based adhesive. The adhesive layer may be made of an ultraviolet-curing resin that is cured by irradiation with ultraviolet rays.

[0028] With the workpiece 11 placed inside the opening 17a of the frame 17, the center of the sheet 19 is attached to the second surface 11b of the workpiece 11, and the outer periphery of the sheet 19 is attached to the frame 17. In this way, the workpiece 11 is supported by the frame 17 via the sheet 19, and a substrate unit (frame unit) 21 is formed in which the workpiece 11, the frame 17, and the sheet 19 are integrated. However, the workpiece 11 does not necessarily have to be supported by the frame 17.

[0029] Next, a processing device (cutting device) for processing the above-mentioned workpiece 11 will be described. Fig. 4 is a perspective view showing a cutting device as a processing device used in the method for processing a workpiece according to the embodiment. As shown in Fig. 1, the cutting device 2 has a chuck table 14.

[0030] The chuck table 14 is configured in a substantially disk shape having a substantially circular first surface 14a and a substantially circular second surface 14b opposite to the first surface 14a. The chuck table 14 has a diameter (width of the first surface 14a or the second surface 14b) slightly larger than the workpiece 11 so as to be able to hold the entire workpiece 11 from below. Specifically, the diameter (width) of the first surface 14a is larger than the diameter (width) of the workpiece 11 by a range of 20 mm to 200 mm.

[0031] A part of the first surface 14a of the chuck table 14 is made of a porous material. The porous material is made of ceramics such as alumina (Al2O3) or silica (SiO2) to have a porous shape.

[0032] A through hole (not shown) is provided inside the chuck table 14. One end of the through hole is connected to a porous body provided on the first surface 14a side. The other end of the through hole is connected to a suction source (not shown). By operating the suction source while the workpiece 11 is in contact with the first surface 14a of the chuck table 14, negative pressure generated from the suction source acts on the first surface 14a via the through hole and the pores of the porous body, and the workpiece 11 is sucked to the first surface 14a. That is, the workpiece 11 is sucked to the chuck table 14 and held thereon.

[0033] The chuck table 14 is connected to a rotation drive source (not shown) such as a motor. The chuck table 14 receives a rotation drive force from the rotation drive source and rotates about a rotation axis 16 that is approximately perpendicular to the first surface 14a.

[0034] The chuck table 14 is supported by a ball screw type chuck table moving mechanism (processing feed mechanism) (not shown) equipped with a ball screw for converting a rotational driving force of a motor or the like into a linear driving force, together with a rotational driving source connected to the chuck table 14. The chuck table 14 moves in a first direction (a direction along the X-axis in FIG. 4) that is substantially parallel to the first surface 14a of the chuck table 14, by the linear driving force of the chuck table moving mechanism.

[0035] The cutting device 2 has a cutting unit 4. The cutting unit 4 includes a spindle 6. A cutting blade 8 is attached to one end (tip end) of the spindle 6. A motor (not shown) is connected to the other end (base end) of the spindle 6. The spindle 6 rotates by receiving a rotational driving force from the motor.

[0036] The cutting unit 4 is supported by a ball screw type cutting unit moving mechanism (indexing feed mechanism, cutting feed mechanism) (not shown) equipped with two sets of ball screws for converting a rotational drive force of a motor or the like into a linear drive force. The cutting unit 4 moves by the linear drive force of this cutting unit moving mechanism along a second direction (direction along the Y axis in FIG. 4) roughly perpendicular to the first direction, and a third direction (direction along the Z axis in FIG. 4) roughly perpendicular to the first and second directions.

[0037] Fig. 5 is a perspective view of the cutting blade 8. As shown in Fig. 5, the cutting blade 8 has an annular base 10 made of a metal such as stainless steel, and an annular cutting edge 12 provided on the periphery of the annular base 10. The base 10 has a hole 10a in the center into which the spindle 6 is inserted. The cutting edge 12 is made of, for example, abrasive grains made of diamond or the like dispersed and fixed by a binder made of resin, metal, or the like, and is configured to have a thickness of 30 μm to 5 mm, typically 3 mm.

[0038] Fig. 6 is a side view of a part (the tip part remote from the base 10) of the cutting blade 12 viewed from a direction perpendicular to the thickness direction of the cutting blade 12. As shown in Fig. 6, the cutting blade 12 has a structure in which an annular first cutting blade portion 24 and an annular second cutting blade portion 26 are laminated in the thickness direction.

[0039] The first cutting edge portion 24 has a first surface 24a that is approximately parallel to the radial direction of the first cutting edge portion 24 and faces the outside of the cutting edge 12, a second surface 24b that is approximately parallel to the first surface 24a and faces the inside of the cutting edge 12, and a third surface 24c that is connected to the outer circumferential edges of the first surface 24a and the second surface 24b and constitutes the tip of the first cutting edge portion 24.

[0040] Similarly, the second cutting edge portion 26 has a first surface 26a that is approximately parallel to the radial direction of the second cutting edge portion 26 and faces the outside of the cutting edge 12, a second surface 26b that is approximately parallel to the first surface 26a and faces the inside of the cutting edge 12, and a third surface 26c that is connected to the outer circumferential edges of the first surface 26a and the second surface 26b and forms the tip of the second cutting edge portion 26. In this embodiment, the second surface 24b of the first cutting edge portion 24 and the second surface 26b of the second cutting edge portion 26 are in close contact with each other.

[0041] The first cutting blade portion 24 has a thickness equal to or greater than the width (radial length) of the first region 25 so that it can cut into the entire first region 25 in the radial direction of the workpiece 11 when it cuts into the workpiece 11. Similarly, the second cutting blade portion 26 has a thickness equal to or greater than the width (radial length) of the second region 27 so that it can cut into the entire second region 27 in the radial direction of the workpiece 11 when it cuts into the workpiece 11.

[0042] The second cutting edge portion 26 is configured to be less susceptible to wear than the first cutting edge portion 24. In other words, the first cutting edge portion 24 is more susceptible to wear than the second cutting edge portion 26. Specifically, when the first cutting edge portion 24 and the second cutting edge portion 26 are used to cut the same target under the same machining conditions, the amount of wear (amount of wear) of the second cutting edge portion 26 is less than the amount of wear (amount of wear) of the first cutting edge portion 24.

[0043] For example, in a configuration in which the average grain size of the abrasive grains of the second cutting edge portion 26 is larger than the average grain size of the abrasive grains of the first cutting edge portion 24, the second cutting edge portion 26 is less likely to wear out than the first cutting edge portion 24. Specifically, when the average grain size of the abrasive grains of the first cutting edge portion 24 is taken as 1, the average grain size of the abrasive grains of the second cutting edge portion 26 is larger than 1 and smaller than 3. In other words, the average grain size of the abrasive grains of the second cutting edge portion 26 is larger than 1 and smaller than 3 times the average grain size of the abrasive grains of the first cutting edge portion 24. The specific average grain size of the abrasive grains is adjusted in consideration of the material of the workpiece, the required quality of processing, and the like.

[0044] The average particle size typically refers to the particle size at 50% cumulative of the particle size distribution measured by a laser diffraction / scattering method (median diameter, d50 diameter, 50% diameter). However, in this embodiment, the average particle size may be calculated by any calculation method as long as it is possible to compare the first cutting edge portion 24 and the second cutting edge portion 26. For example, the particle sizes of a plurality of abrasive grains may be calculated from an image obtained by observation with an electron microscope, and the average value of the particle sizes obtained by averaging may be used as the average particle size.

[0045] In addition, when the concentration of abrasive grains in the second cutting edge portion 26 is greater than the concentration of abrasive grains in the first cutting edge portion 24, the second cutting edge portion 26 is less likely to wear out than the first cutting edge portion 24. Here, the concentration of abrasive grains in the first cutting edge portion 24 is 3 Similarly, the concentration of abrasive grains in the second cutting edge portion 26 is expressed as the concentration of abrasive grains per cm 3 of the second cutting edge portion 26. 3 It means the volume of abrasive grains contained per unit (i.e., volume %).

[0046] Specifically, when the concentration of abrasive grains in the first cutting edge portion 24 is taken as 1, the concentration of abrasive grains in the second cutting edge portion 26 is greater than 1 and not greater than 20. In other words, the concentration of abrasive grains in the second cutting edge portion 26 is greater than 1 and not greater than 20 times the concentration of abrasive grains in the first cutting edge portion 24. The specific concentration is adjusted in consideration of the material of the workpiece, the required processing quality, and the like.

[0047] Furthermore, even if the hardness of the binder of the second cutting edge portion 26 is greater than that of the binder of the first cutting edge portion 24, the second cutting edge portion 26 is less likely to wear than the first cutting edge portion 24. Hardness is evaluated, for example, by Vickers hardness (HV), Rockwell hardness (HR), or Brinell hardness (HB), and all of these are measured by a commercially available hardness tester. The specific Vickers hardness is adjusted in consideration of the material of the workpiece, the required machining quality, and the like.

[0048] The cutting device 2 also has one or more transport mechanisms (not shown) capable of transporting the above-mentioned workpiece 11 to the chuck table 14 or the like. The transport mechanism is, for example, a robot arm. The workpiece 11 is transported by this transport mechanism onto the first surface 14a of the chuck table 14 so that the first surface 11a of the workpiece 11 is exposed. The workpiece 11 is also transported by the transport mechanism from the first surface 14a of the chuck table 14 to the outside of the chuck table 14.

[0049] A controller 18 is connected to the various components of the cutting device 2 described above. The operation of each component is controlled by this controller 18. The controller 18 is configured by a computer including a processing device 20 such as a CPU (Central Processing Unit) and a storage device 22 consisting of a main storage device such as a DRAM (Dynamic Random Access Memory) and / or an auxiliary storage device such as a hard disk drive or a flash memory.

[0050] The functions of the controller 18 are realized by the processing device 20 operating in accordance with a program (software) stored in the storage device 22. However, the controller 18 may be realized only by hardware. Note that more specific functions of the controller 18 will be explained in the explanation of the method for processing a workpiece.

[0051] Next, a method for processing a workpiece according to an embodiment will be described. Fig. 7 is a flow diagram of the method for processing a workpiece according to an embodiment. As shown in Fig. 7, the method for processing a workpiece according to this embodiment includes a holding step S1, a position adjustment step S2, and a cutting step S3. In this embodiment, each step constituting the method for processing a workpiece is performed based on a command from the controller 18.

[0052] In the holding step S1, the workpiece 11 is held on the first surface 14a of the chuck table 14. Specifically, for example, the above-mentioned conveying mechanism carries the workpiece 11 from outside the cutting device 2 into the chuck table 14, and the workpiece 11 is placed on the first surface 14a of the chuck table 14. As described above, in this embodiment, the second surface 11b side of the workpiece 11 is placed on the first surface 14a of the chuck table 14 so that the first surface 11a of the workpiece 11 is exposed.

[0053] Thereafter, when negative pressure from the suction source is applied to the first surface 14a under the control of the controller 18, the workpiece 11 is sucked onto the first surface 14a of the chuck table 14. That is, the workpiece 11 is held by the first surface 14a of the chuck table 14. Note that the workpiece 11 may be placed on the first surface 14a of the chuck table 14 manually by an operator or the like.

[0054] Next, a position adjustment step S2 is performed. In the position adjustment step S2, the positional relationship between the cutting blade 8 of the cutting unit 4 and the workpiece 11 held by the chuck table 14 is adjusted in a first direction (direction along the X-axis) and a second direction (direction along the Y-axis).

[0055] Typically, the positional relationship between the cutting blade 8 and the workpiece 11 is adjusted so that the lower end of the first cutting edge portion 24 of the cutting blade 8 is positioned directly above the first region 25 of the chamfered portion 23 of the workpiece 11. Also, the positional relationship between the cutting blade 8 and the workpiece 11 is adjusted so that the lower end of the second cutting edge portion 26 of the cutting blade 8 is positioned directly above the second region 27 of the workpiece 11. That is, to realize such a positional relationship, the position of the chuck table 14 in the first direction is adjusted by the chuck table moving mechanism, and the position of the cutting unit 4 in the second direction is adjusted by the cutting unit moving mechanism.

[0056] Next, the cutting step S3 is performed. Fig. 8 is a side view showing the workpiece 11, the cutting blade 12, etc. in the cutting step S3 of the method for processing a workpiece according to the embodiment. In the cutting step S3, while the cutting blade 8 is rotating, the cutting blade 8 and the workpiece 11 move relatively along the third direction (direction along the Z-axis). That is, the motor rotates the spindle 6, and then the cutting unit moving mechanism lowers the cutting unit 4 along the third direction.

[0057] Furthermore, while the cutting unit moving mechanism lowers the cutting unit 4, the workpiece 11 held by the chuck table 14 rotates. That is, the rotary drive source connected to the chuck table 14 rotates the chuck table 14 about the rotation axis 16 in accordance with the descent of the cutting blade 8.

[0058] In this manner, by rotating the chuck table 14 around the rotation axis 16 while lowering the cutting blade 8, the cutting blade 8 can cut into the entire chamfered portion 23 provided on the outer periphery of the workpiece 11. Therefore, the chamfered portion 23 of the workpiece 11 is cut and removed by the cutting blade 8.

[0059] In this embodiment, the cutting blade 8 is lowered to a depth where it slightly cuts into the sheet 19. For example, when the thickness of the workpiece 11 is 775 μm, the cutting depth of the cutting blade 8 is set to 800 μm. Also, in this embodiment, the rotation speed of the spindle 6 is set to 30,000 rpm, and the rotation speed of the chuck table 14 is set to 72 deg / s. However, the cutting conditions are not limited to these and are appropriately set depending on the material and thickness of the workpiece 11.

[0060] When the chamfered portion 23 of the workpiece 11 is completely removed, the series of steps of the workpiece processing method according to this embodiment is completed. The dotted line portion in Fig. 8 indicates the portion that has been cut and removed by the cutting blade 8 (i.e., the chamfered portion 23 of the workpiece 11).

[0061] As described above, in the method for processing a workpiece according to the embodiment, a cutting blade 8 is used that has a first cutting edge portion 24 and a second cutting edge portion 26 that is less susceptible to wear than the first cutting edge portion 24. The first cutting edge portion 24 cuts into a first region 25 located on the inside within the outer periphery of the workpiece 11, and the second cutting edge portion 26 cuts into a second region 27 located on the outside within the outer periphery of the workpiece 11.

[0062] In a cutting blade having a single cutting edge, the outer part of the cutting blade that processes the outer second region is usually more likely to wear out than the inner part of the cutting blade that processes the inner first region. Therefore, by cutting the second cutting edge, which is relatively less likely to wear out, into this second region, the difference in the degree of wear between the first cutting edge and the second cutting edge is less likely to occur, and uneven wear of the cutting blade is suppressed. This reduces the frequency of dressing operations.

[0063] The method for processing a workpiece according to this embodiment is also used when processing a laminated wafer in which multiple wafers are bonded together. Fig. 9 is a perspective view of the laminated wafer as the workpiece, and Fig. 10 is a side view of the laminated wafer. As shown in Figs. 9 and 10, the workpiece 29, which is a laminated wafer, is formed by stacking a first wafer 31 and a second wafer 33.

[0064] The size and material of the first wafer 31 and the size and material of the second wafer 33 are similar to those of the workpiece 11. Furthermore, like the workpiece 11, the streets 13 and devices 15 are formed on the first surface 31a of the first wafer 31 and the first surface 33a of the second wafer 33. However, the streets 13 and the devices 15 may be formed on only one of the first wafer 31 and the second wafer 33. Furthermore, the streets 13 and the devices 15 do not have to be formed on both the first wafer 31 and the second wafer.

[0065] For example, the first wafer 31 and the second wafer 33 constituting the workpiece 29 are bonded by heating the first wafer 31 and the second wafer 33 while they are in contact with each other, thereby causing the elements contained in the first wafer 31 and the second wafer 33 to diffuse into each other.

[0066] Also, for example, the first wafer 31 and the second wafer 33 are joined by applying an adhesive to either the first wafer 31 or the second wafer 33 and bonding the first wafer 31 and the second wafer 33 together via this adhesive.

[0067] 10, the first wafer 31 has a chamfered portion 35 formed by removing the corners of the outer periphery of the first wafer 31 to form a rounded chamfered portion 35 in an annular shape along the outer periphery of the first wafer 31. The chamfered portion 35 includes a first region 37 and a second region 39 located outside the first region 37 in the radial direction of the workpiece 29.

[0068] Similarly, the second wafer 33 has a chamfered portion 41 formed by removing the corners of the outer periphery of the second wafer 33 to form a rounded chamfered portion 41 in an annular shape along the outer periphery of the second wafer 33. The chamfered portion 41 includes a first region 43 and a second region 45 located outside the first region 43 in the radial direction of the workpiece 29.

[0069] A specific method for processing the workpiece 29 may be the same as that for processing the workpiece 11. In this manner, the method for processing a workpiece according to this embodiment can also be applied to processing the workpiece 29, which is a laminated wafer.

[0070] Next, a method for processing a workpiece according to a first modified example of the embodiment will be described. Fig. 11 is a side view of a part (the tip part remote from the base 10) of the cutting edge 28 of the cutting blade 36 used in the method for processing a workpiece according to the first modified example, viewed from a direction perpendicular to the thickness direction. In this modified example, a cutting device 2 similar to that in the embodiment is used. However, in this modified example, a cutting blade 36 having a cutting edge 28 shown in Fig. 11 is used instead of the cutting blade 8. The cutting edge 28 is configured to have a thickness of 30 μm to 5 mm, typically 3 mm.

[0071] 11, the cutting blade 28 has a structure in which an annular first cutting blade portion 30, an annular second cutting blade portion 32, and an annular third cutting blade portion 34 are laminated in the thickness direction. The first cutting blade portion 30 has a first surface 30a that is approximately parallel to the radial direction of the first cutting blade portion 30 and faces the outside of the cutting blade 28, a second surface 30b that is approximately parallel to the first surface 30a and faces the inside of the cutting blade 28, and a third surface 30c that is connected to the outer circumferential edges of the first surface 30a and the second surface 30b and forms the tip of the first cutting blade portion 30.

[0072] Similarly, the third cutting edge portion 34 has a first surface 34a that is approximately parallel to the radial direction of the third cutting edge portion 34 and faces the outside of the cutting edge 28, a second surface 34b that is approximately parallel to the first surface 34a and faces the inside of the cutting edge 28, and a third surface 34c that is connected to the outer circumferential edges of the first surface 34a and the second surface 34b and forms the tip of the third cutting edge portion 34.

[0073] Similarly, the second cutting edge portion 32 has a first surface 32a that is approximately parallel to the radial direction of the second cutting edge portion 32 and contacts the second surface 30b of the first cutting edge portion 30, a second surface 32b that is approximately parallel to the radial direction of the second cutting edge portion 32 and contacts the second surface 34b of the third cutting edge portion 34, and a third surface 32c that is connected to the outer circumferential edges of the first surface 32a and the second surface 32b and forms the tip of the second cutting edge portion 32. That is, in this modification, the second surface 30b of the first cutting edge portion 30 and the first surface 32a of the second cutting edge portion 32 are in close contact with each other, and the second surface 34b of the third cutting edge portion 34 and the second surface 32b of the second cutting edge portion 32 are in close contact with each other.

[0074] The first cutting edge portion 30 and the second cutting edge portion 32 are formed by dispersing and fixing abrasive grains made of, for example, diamond, etc., with a binder made of, for example, resin, metal, etc., in the same manner as the cutting edge 12 used in the embodiment. On the other hand, the third cutting edge portion 34 does not include abrasive grains, and is formed only with a binder, for example.

[0075] The first cutting blade portion 30 has a thickness equal to or greater than the width (radial length) of the first region 25 so that it can cut into the entire first region 25 in the radial direction of the workpiece 11 when cutting into the workpiece 11. Similarly, the second cutting blade portion 32 has a thickness equal to or greater than the width (radial length) of the second region 27 so that it can cut into the entire second region 27 in the radial direction of the workpiece 11 when cutting into the workpiece 11.

[0076] Since the third cutting edge portion 34 does not cut into the workpiece 11, the thickness of the third cutting edge portion 34 can be set arbitrarily without depending on the thickness of the first cutting edge portion 24 or the thickness of the second cutting edge portion 32.

[0077] For example, the thickness of the first cutting edge portion 30 is 10 μm or more and 3 mm or less, typically 1 mm. The thickness of the second cutting edge portion 32 is 10 μm or more and 3 mm or less, typically 1 mm. The thickness of the third cutting edge portion 34 is 10 μm or more and 3 mm or less, typically 1 mm.

[0078] The second cutting edge portion 32 is configured to be less susceptible to wear than the first cutting edge portion 30. On the other hand, the third cutting edge portion 34 is configured to be more susceptible to wear than the first cutting edge portion 30. In other words, the second cutting edge portion 32 is least susceptible to wear, and the third cutting edge portion 34 is most susceptible to wear. Specifically, parameters such as the average grain size of the abrasive grains, the concentration of the abrasive grains, and the hardness of the binder are adjusted in accordance with the above-described embodiment.

[0079] The method for processing a workpiece according to this modification includes a holding step, a position adjustment step, and a cutting step, similar to the embodiment. The holding step in the method for processing a workpiece according to this modification is performed in the same manner as the holding step S1 in the embodiment.

[0080] In the position adjustment step in the workpiece processing method of this modified example, the positional relationship between the cutting blade 36 of the cutting unit 4 and the workpiece 11 held by the chuck table 14 is adjusted in a first direction (direction along the X-axis) and a second direction (direction along the Y-axis).

[0081] Typically, the positional relationship between the cutting blade 36 and the workpiece 11 is adjusted so that the lower end of the first cutting edge portion 30 of the cutting blade 36 is positioned directly above the first region 25 of the chamfered portion 23 of the workpiece 11. In addition, the positional relationship between the cutting blade 36 and the workpiece 11 is adjusted so that the lower end of the second cutting edge portion 32 of the cutting blade 36 is positioned directly above the second region 27 of the workpiece 11.

[0082] Furthermore, the positional relationship between the cutting blade 36 and the workpiece 11 is adjusted so that the lower end of the third cutting edge portion 34 is positioned above a third region 47 that is positioned radially outward of the outer periphery of the workpiece 11. That is, to realize such a positional relationship, the position of the chuck table 14 in the first direction is adjusted by the chuck table moving mechanism, and the position of the cutting unit 4 in the second direction is adjusted by the cutting unit moving mechanism.

[0083] Next, the cutting step is performed. Fig. 12 is a side view showing the workpiece 11 and the cutting blade 28 in the cutting step of the workpiece processing method according to the first modified example. The dotted line in Fig. 12 indicates the part that has been cut and removed by the cutting blade 8 (i.e., the chamfered portion 23 of the workpiece 11).

[0084] In the cutting step according to the first modified example, the operation and processing conditions of the cutting device 2 are the same as those in the cutting step S3 according to the embodiment. Since the cutting blade 36 and the workpiece 11 are in the positional relationship adjusted in the position adjustment step described above, the third cutting edge portion 34 of the cutting blade 8 does not cut into the workpiece 11.

[0085] As described above, in this modification, since the third cutting edge portion 34 does not cut the workpiece 11, it is not necessary to include abrasive grains, and is composed of only a binder. When dressing the cutting edge 28, a cutting edge containing abrasive grains takes more time than a cutting edge not containing abrasive grains. In this modification, a part of the cutting edge 28 is composed of the third cutting edge portion 34 not containing abrasive grains, so that the dressing time can be shortened. In addition, the cutting edge 28 composed of the first cutting edge portion 30, the second cutting edge portion 32, and the third cutting edge portion 34 has a larger overall thickness than a cutting edge composed of only the first cutting edge portion 30 and the second cutting edge portion 32, and therefore the resistance of the cutting blade 36 to external forces is increased accordingly. However, the third cutting edge portion 34 may contain abrasive grains.

[0086] Next, a method for processing a workpiece according to the second modified example will be described. The method for processing a workpiece according to this modified example includes a holding step, a position adjustment step, and a cutting step, similar to the embodiment and the first modified example. The holding step and the position adjustment step are performed in the same manner as the holding step and the position adjustment step of the first modified example.

[0087] Fig. 13 is a side view showing the workpiece 11 and the cutting blade 28 in the cutting step of the workpiece processing method according to the second modified example. As shown in Fig. 13, in the cutting step of this modified example, the cutting blade 36 cuts into the lower surface of the workpiece 11, that is, to a depth that does not reach the second surface 11b.

[0088] For example, when the workpiece 11 is thinned by a subsequent grinding process, it is important that the chamfered portion 23, which has been thinned to a knife edge by the grinding process, does not remain on the outer periphery of the workpiece 11. In this case, therefore, in the cutting step, it is sufficient to remove the chamfered portion 23 of the workpiece 11 to a depth equivalent to the thickness of the workpiece 11 after the grinding process (finishing thickness).

[0089] In such a case, for example, as a processing condition, the cutting depth of the cutting blade 36 (the cutting depth set in the cutting device 2) is set to be equal to or greater than the finished thickness of the workpiece 11 after the grinding process. A specific cutting depth is, for example, 5 μm or more and 800 μm or less, but this cutting depth can be freely changed depending on the finished thickness of the workpiece 11. Other processing conditions are the same as those in the embodiment and the first modified example.

[0090] Next, a method for processing a workpiece according to a third modified example of the embodiment will be described. In this modified example, a workpiece 29 shown in Fig. 9 is used as the workpiece. Fig. 14 is a side view showing the workpiece 11 and a cutting blade 28 in a cutting step of the method for processing the workpiece 11 according to the third modified example.

[0091] 14, in the cutting step of this modified example, the workpiece 29 is machined by the cutting blade 36 used in the first and second modified examples. Specifically, the cutting blade 36 is caused to cut from the first surface 33a of the second wafer 33 to a depth that does not reach the underside of the first wafer 31, i.e., the second surface 33b. As a result, the chamfered portion 41 of the second wafer 33 is entirely cut and removed. On the other hand, only a portion of the chamfered portion 35 of the first wafer 31 on the second wafer 33 side is cut and removed.

[0092] As described above, according to the above-mentioned embodiment and each of the modified examples, it is possible to provide a method for processing a workpiece in which the cutting blade 8 or the cutting blade 36 is less likely to wear unevenly when removing the outer periphery of the workpiece 11 (chamfered portion 23) or the outer periphery of the workpiece 29 (chamfered portion 35 and chamfered portion 41) with the cutting blade 8 or the cutting blade 36.

[0093] The present invention is not limited to the above-described embodiment and each modified example, and may be implemented in various ways. For example, in the cutting step S3 according to the above-described embodiment, the cutting blade 8 is rotated by the motor, and then the cutting unit moving mechanism lowers the cutting blade 8. However, the cutting blade 8 may be lowered by the cutting unit moving mechanism, and the cutting blade 8 may be rotated by the motor after the cutting blade 8 comes into contact with the workpiece 11.

[0094] Also, instead of rotating the chuck table 14, the cutting blade 8 may move in a circular manner along the outer periphery of the workpiece 11. Furthermore, instead of lowering the cutting blade 8, the chuck table 14 may rise.

[0095] In addition, in the cutting step S3 in the above-described embodiment, the cutting blade 8 is continuously lowered while rotating the cutting blade 8 and the chuck table 14, thereby cutting the cutting blade 8 from the first surface 11a of the workpiece 11 to the sheet 19, but the descent of the cutting blade 8 may be divided into multiple steps, and cutting of the workpiece 11 may be performed in stages.

[0096] In this case, for example, the cutting depth of the cutting blade 8 in one descent is set to 5 μm or more and 300 μm or less, and the number of repetitions of descent and cutting is set to 2 times or more and 20 times or less.

[0097] In addition, the structures, methods, and the like according to the above-described embodiments and modifications may be implemented without departing from the scope of the present invention. [Explanation of symbols]

[0098] 11: Workpiece 11a: 1st page 11b: 2nd side 11c: Notch 13: Street 15: Device 17: Frame 17a:Aperture 19:Sheet 21: Circuit board unit (frame unit) 23: Chamfered part 25: 1st area 27:Second area 29: Workpiece (stacked wafer) 31: First wafer 31a: 1st page 31b: 2nd side 33: 2nd wafer 33a: 1st page 33b: 2nd side 35: Chamfered part 37: 1st area 39:Second area 41: Chamfered part 43:First area 45:Second area 47:Third area 2:Cutting device 4: Cutting unit 6: Spindle 8: Cutting blade 10: Foundation 10a: Hole 12: Cutting edge 14: Chuck table 16: Rotation axis 18: Controller 20: Processing section 22: Storage section 24: 1st cutting edge part 24a: 1st page 24b: 2nd side 24c: 3rd side 26: 2nd cutting edge part 28: Cutting edge 30: First cutting edge 30a: 1st side 30b: 2nd side 30c: 3rd side 32: Second cutting edge 32a: 1st page 32b: 2nd side 32c: 3rd side 34: 3rd cutting edge 34a: 1st page 34b: 2nd side 34c: 3rd side 36: Cutting blade

Claims

1. A method for machining a workpiece that is applied when machining an outer periphery of a disk-shaped workpiece having a circular first surface and a second surface, comprising: a holding step of holding the second surface side of the workpiece so that the first surface of the workpiece is exposed; After the holding step, a cutting step is performed in which, while rotating an annular cutting blade having an annular first cutting edge portion and an annular second cutting edge portion which is less susceptible to wear than the first cutting edge portion, the first cutting edge portion is caused to cut into a first region within the outer periphery and the second cutting edge portion is caused to cut into a second region within the outer periphery which is located radially outward of the first region within the outer periphery, and the cutting blade is moved relatively along the outer periphery of the workpiece, thereby cutting the outer periphery of the workpiece.

2. 2. The method for machining a workpiece according to claim 1, wherein the cutting blade further comprises an annular third cutting edge portion which is more easily worn than the first cutting edge portion.

3. The cutting blade has a laminated structure in which the first cutting edge portion, the second cutting edge portion, and the third cutting edge portion are laminated such that the second cutting edge portion contacts the first cutting edge portion and the third cutting edge portion contacts the second cutting edge portion, The method for machining a workpiece according to claim 2 , wherein in the cutting step, the third cutting edge portion is disposed in a third region located radially outward from the outer periphery.

4. 4. The method for machining a workpiece according to claim 3, wherein the third cutting edge portion contains a binder but does not contain abrasive grains.

5. the workpiece is a bonded wafer obtained by bonding a first wafer having a chamfered outer periphery to a second wafer; 5. A method for processing a workpiece as described in any one of claims 1 to 4, wherein in the cutting step, the cutting blade is caused to cut from the first surface side of the workpiece on which the first wafer is placed to a position not reaching the second surface.

6. The first cutting edge portion and the second cutting edge portion each include an abrasive grain and a bonding material, 5. A method for processing a workpiece as described in any one of claims 1 to 4, wherein the grain size of the abrasive grains contained in the second cutting edge portion is larger than the grain size of the abrasive grains contained in the first cutting edge portion, the concentration of the abrasive grains contained in the second cutting edge portion is higher than the concentration of the abrasive grains contained in the first cutting edge portion, or the hardness of the binder of the abrasive grains contained in the second cutting edge portion is higher than the hardness of the binder contained in the first cutting edge portion.

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