Workpiece processing method

Abstract

To provide a workpiece processing method that reduces the risk of cracks occurring in a second wafer when removing the peripheral portion on the first wafer side of a workpiece in which a first wafer and a second wafer are bonded via a bonding layer, and that can remove the peripheral portion with a targeted cutting depth.SOLUTION: A workpiece processing method includes a first trimming step 1002 of rotating a first cutting blade in a cutting direction from the second wafer side of the workpiece toward the first wafer side, cutting and removing the peripheral portion while cutting the first cutting blade into the peripheral portion of the first wafer side of the workpiece, and a second trimming step 1003 of rotating a second cutting blade in a cutting direction from the first wafer side of the workpiece toward the second wafer side, cutting and removing the peripheral portion while cutting the second cutting blade from the first wafer side of the workpiece to a cutting depth deeper than that of the first trimming step 1002.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for processing a workpiece by removing a peripheral portion on the first wafer side of a workpiece in which a first wafer and a second wafer are joined via a bonding layer.

Background Art

[0002] When grinding the back surface of a wafer (workpiece) whose peripheral portion is chamfered, the peripheral portion is formed into an acute angle, and cracks or chips may occur starting from that portion. Therefore, before grinding, edge trimming is performed to cut and remove part or all of the chamfered portion along the outer periphery of the workpiece with a cutting blade (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, when performing edge trimming, a so-called down cut is performed in which a cutting blade rotates from the upper surface to the lower surface of the workpiece in the forward direction of the moving direction of the workpiece while cutting into the workpiece. In this way, when edge trimming is performed on a workpiece in which a first wafer and a second wafer are joined via a bonding layer, there is a problem that chips (cutting chips) generated in the upper first wafer are pressed against the second wafer located below the workpiece, causing cracks in the second wafer. In particular, when the bonding state of the bonding region on the outer peripheral side of the workpiece is poor, the outer peripheral region of the first wafer is likely to peel off, generating large chips (cutting chips), and thus there is a problem that cracks are likely to occur in the second wafer.

[0005] Therefore, it is conceivable to perform so-called up-cutting in which the cutting blade rotates from the lower surface to the upper surface of the workpiece in the forward direction of the movement direction of the workpiece while cutting into the workpiece. However, when cutting the peripheral portion of the first wafer by up-cutting, the cutting blade is less likely to bite into the first wafer compared to down-cutting. As a result, the cutting blade fails to cut the first wafer and escapes upward, resulting in a cut that is shallower than the targeted cutting depth, and the peripheral portion of the first wafer finishes thick.

[0006] The present invention has been made in view of such problems, and an object thereof is to provide a method for processing a workpiece that reduces the risk of cracking the second wafer when removing the peripheral portion on the first wafer side of a workpiece in which the first wafer and the second wafer are joined via a bonding layer, and can remove the peripheral portion at a targeted cutting depth.

Means for Solving the Problems

[0007] In order to solve the above-described problems and achieve the object, a method for processing a workpiece according to the present invention is a method for processing a workpiece for removing a peripheral portion on the first wafer side of a workpiece in which a first wafer and a second wafer are joined via a bonding layer, the method including: a holding step of holding the second wafer side of the workpiece on a holding surface of a holding table; a first trimming step of cutting and removing the peripheral portion while cutting a first cutting blade into the peripheral portion on the first wafer side of the workpiece held in the holding step; and a second trimming step of cutting and removing the peripheral portion while cutting a second cutting blade into the peripheral portion at a predetermined cutting depth deeper than the cutting depth of the first trimming step, from the first wafer side of the workpiece held in the holding step after the first trimming step. The first trimming step rotates the first cutting blade in a rotation direction for cutting from the second wafer side to the first wafer side of the workpiece, and the second trimming step rotates the second cutting blade in a rotation direction for cutting from the first wafer side to the second wafer side of the workpiece.

[0008] The first cutting blade in the first trimming step may not cut into the second wafer.

[0009] The abrasive grains of at least one of the first cutting blade and the second cutting blade may have an abrasive grain size smaller than 30 μm.

Advantages of the Invention

[0010] In the present invention, in the first trimming step, the first cutting blade is rotated in the rotational direction of cutting from the second wafer side to the first wafer side of the workpiece in front of the relative movement direction of the first cutting blade with respect to the workpiece, so as to cut and remove the peripheral portion of the first wafer. And in the second trimming step, the second cutting blade is rotated in the rotational direction of cutting from the first wafer side to the second wafer side of the workpiece in front of the relative movement direction of the second cutting blade with respect to the workpiece, so as to cut and remove the peripheral portion of the first wafer. Therefore, when removing the peripheral portion on the first wafer side of the workpiece in which the first wafer and the second wafer are bonded via the bonding layer, the risk of generating cracks in the second wafer is reduced, and the removal can be achieved with the targeted cutting depth.

Brief Description of the Drawings

[0011]

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DETAILED DESCRIPTION OF THE INVENTION

[0012] The embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and substantially identical ones. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[0013] 〔Embodiment〕 A method for processing a workpiece according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing the processing procedure of the method for processing a workpiece according to the embodiment. As shown in FIG. 1, the method for processing a workpiece according to the embodiment includes a holding step 1001, a first trimming step 1002, and a second trimming step 1003. The method for processing a workpiece according to the embodiment is a method for removing the peripheral portion on the first wafer 110 side of a workpiece 100 (see FIGS. 2 and 3) in which a first wafer 110 and a second wafer 120 are joined via a bonding layer 130.

[0014] FIG. 2 is a perspective view showing a configuration example of a workpiece 100 that is a processing target of a processing method for a workpiece according to an embodiment. FIG. 3 is a cross-sectional view showing the workpiece 100 of FIG. 2. As shown in FIGS. 2 and 3, the workpiece 100 that is a processing target of the processing method for a workpiece according to an embodiment is a so-called laminated wafer including a first wafer 110, a second wafer 120, and a bonding layer 130 that bonds the first wafer 110 and the second wafer 120.

[0015] Both the first wafer 110 and the second wafer 120 are wafers such as disk-shaped semiconductor device wafers or optical device wafers having, for example, silicon, sapphire, silicon carbide (SiC), gallium arsenide, etc. as a base material. As shown in FIG. 3, both the first wafer 110 and the second wafer 120 have chamfered peripheral portions over the entire circumference. The first wafer 110 and the second wafer 120 may be the same wafer as each other or different wafers from each other. The first wafer 110 and the second wafer 120 are laminated via the bonding layer 130 so that their central axes generally overlap, and are bonded by the bonding layer 130 to form the workpiece 100.

[0016] In the present embodiment, the first wafer 110 and the second wafer 120 include a plurality of planned division lines formed in a grid pattern on a flat surface, and a device (device 140 in the example shown in FIG. 2) is formed in a region partitioned by the plurality of planned division lines. In the present embodiment, as shown in FIG. 2, the surface side of the first wafer 110 where the device 140 is formed is bonded to the second wafer 120 via the bonding layer 130, and the back surface on the side opposite to the surface side where the device 140 of the first wafer 110 is formed is the exposed surface, and this exposed surface becomes the surface to be ground after the peripheral portion is removed by implementing the processing method for the workpiece according to the embodiment. Note that the first wafer 110 and the second wafer 120 are not limited to the form in which the device 140 is formed in the present invention, and the device 140 may not be formed on one or both of the first wafer 110 and the second wafer 120.

[0017] The bonding layer 130 is, for example, an adhesive made of resin such as benzocyclobutene, a silicon oxide (SiO2) layer, a first active layer formed by subjecting a bonding surface of the first wafer 110 to be bonded to the second wafer 120 to a surface activation treatment, a second active layer formed by subjecting a bonding surface of the second wafer 120 to be bonded to the first wafer 110 to a surface activation treatment, and the like. When the first wafer 110 and the second wafer 120 are made of silicon as a base material, the bonding layer 130 may be a silicon oxide film layer formed on the bonding surfaces of the first wafer 110 and the second wafer 120.

[0018] FIG. 4 is a perspective view showing a configuration example of a processing apparatus 1 that implements a processing method for a workpiece according to an embodiment. As shown in FIG. 4, a processing apparatus 1 that implements a processing method for a workpiece according to an embodiment includes a holding table 10, a processing unit 20, an X-axis direction moving unit 31, a Y-axis direction moving unit 32, a Z-axis direction moving unit 33, a rotation driving unit 35, and a control unit 40.

[0019] As shown in FIG. 4, the holding table 10 is a so-called chuck table including a disk-shaped frame body in which a recess is formed and a disk-shaped suction portion fitted into the recess. The suction portion of the holding table 10 is formed of a porous ceramic or the like having a large number of porous holes and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). The upper surface of the suction portion of the holding table 10 is a holding surface 11 on which the workpiece 100 is placed and the placed workpiece 100 is suction-held by a negative pressure introduced from the vacuum suction source. The holding surface 11 and the upper surface of the frame body of the holding table 10 are arranged on the same plane and are formed parallel to the XY plane, which is a horizontal plane. The holding table 10 is provided so as to be movable along the X-axis direction parallel to the horizontal direction by the X-axis direction moving unit 31. The rotation driving unit 35 is provided below the frame body and the suction portion of the holding table 10, and the holding table 10 is provided so as to be rotatable (rotatable) around a central axis 12 (see FIG. 6 and the like) parallel to the Z-axis direction passing through the center of the holding surface 11 and parallel to the vertical direction by the rotation driving unit 35.

[0020] In this embodiment, as shown in FIG. 4, the processing unit 20 includes a first processing unit 20-1 and a second processing unit 20-2. The first processing unit 20-1 and the second processing unit 20-2 have substantially the same configuration. Hereinafter, when distinguishing each part related to the first processing unit 20-1 from each part related to the second processing unit 20-2, “-1” is added after the reference numeral for notation. When distinguishing each part related to the second processing unit 20-2 from each part related to the first processing unit 20-1, “-2” is added after the reference numeral for notation. When there is no need to distinguish between the first processing unit 20-1 and the second processing unit 20-2, the corresponding parts are described as common to both, and “-1” and “-2” are not added after the reference numeral and are appropriately omitted. Also, when explaining the parts with the same configuration of the first processing unit 20-1 and the second processing unit 20-2, or when not particularly distinguishing, they are abbreviated as the processing unit 20.

[0021] As shown in FIG. 4, the processing unit 20 includes a cutting blade 21 and a spindle 22. The cutting blade 21 is attached to the tip of the spindle 22 and cuts the workpiece 100 held on the holding table 10 by being rotated by the spindle 22 serving as the rotation axis. In the first embodiment, the cutting blade 21 is, for example, a cutting grindstone having an annular cutting edge in which abrasive grains such as diamond or CBN (Cubic Boron Nitride) are fixed with a bonding material (binder) such as metal or resin and formed to a predetermined thickness. The cutting blade 21 may be a hubless blade or a hub blade in which an annular cutting edge is fixed to the outer periphery of an annular base.

[0022] The spindle 22 is rotatably provided around an axis parallel to the horizontal direction and parallel to the Y-axis direction orthogonal to the X-axis direction, and is rotated around the axis by a motor (not shown) connected to the spindle 22. The spindle 22 rotatably supports the cutting blade 21 attached to the tip of the spindle 22 around an axis parallel to the Y-axis direction.

[0023] That is, in the example of the present embodiment shown in FIG. 4, the first processing unit 20-1 of the processing unit 20 includes a first spindle 22-1 with its tip directed in the -Y direction, and a first cutting blade 21-1 rotatably fixed to the tip of the first spindle 22-1 together with the first spindle 22-1. The second processing unit 20-2 of the processing unit 20 includes a second spindle 22-2 with its tip directed in the +Y direction, and a second cutting blade 21-2 rotatably fixed to the tip of the second spindle 22-2 together with the second spindle 22-2.

[0024] In the present embodiment, the abrasive grains included in at least one of the first cutting blade 21-1 and the second cutting blade 21-2, that is, the abrasive grains fixed by the bonding material in the cutting blade 21, preferably have a particle size of #700 (No. 700) or more and #2000 (No. 2000) or less. Here, the particle size of the abrasive grains included in the cutting blade 21 is a parameter defined by the JIS standard "R6001: Particle Size of Grinding and Honing Abrasives", where the number becomes smaller as the center particle size becomes larger, and the number becomes larger as the center particle size becomes smaller. Based on this definition, when converting the particle size to the particle diameter (abrasive grain diameter) of the abrasive grains, in the present embodiment, the abrasive grains included in at least one of the first cutting blade 21-1 and the second cutting blade 21-2 preferably have an abrasive grain diameter of 5 μm or more and less than 30 μm. In the present invention, the abrasive grains included in the first cutting blade 21-1 and the abrasive grains included in the second cutting blade 21-2 may both have an abrasive grain diameter of 5 μm or more and less than 30 μm.

[0025] The first processing unit 20-1 is provided so as to be movable in the Y-axis direction and the Z-axis direction by a Y-axis direction moving unit 32 and a Z-axis direction moving unit 33, respectively, independently of the second processing unit 20-2. Also, the second processing unit 20-2 is provided so as to be movable in the Y-axis direction and the Z-axis direction by a Y-axis direction moving unit 32 and a Z-axis direction moving unit 33, respectively, independently of the first processing unit 20-1. The processing apparatus 1 thus includes two sets of the first processing unit 20-1 and the second processing unit 20-2, that is, a die sinker with two spindles, namely, a so-called facing dual type processing apparatus.

[0026] The X-axis direction moving unit 31 moves the holding table 10 along the X-axis direction relative to the processing unit 20 (the first processing unit 20-1 and the second processing unit 20-2). The Y-axis direction moving unit 32 and the Z-axis direction moving unit 33 move the processing unit 20 (the first processing unit 20-1 or the second processing unit 20-2) along the Y-axis direction and the Z-axis direction, respectively, relative to the holding table 10. The rotation drive unit 35 rotates the holding table 10 relative to the processing unit 20 (the first processing unit 20-1 and the second processing unit 20-2) around the central axis 12 of the holding surface 11.

[0027] Under the control of the control unit 40, the processing unit 20 is positioned at a position vertically facing the peripheral edge of the workpiece 100 held by the holding table 10. With the cutting blade 21, a rotational operation around an axis parallel to the Y-axis direction is added by the rotational operation of the spindle 22. In a state where the cutting blade 21 is cut into a predetermined cutting depth from the upward-facing surface of the peripheral edge of the workpiece 100, the holding table 10 that holds the workpiece 100 is rotated around the central axis 12 of the holding surface 11 by the rotation drive unit 35, and a so-called edge trimming process is performed in which the entire circumference of the peripheral edge of the workpiece 100 is cut in a circular shape for chamfering.

[0028] The control unit 40 controls the operations of various components of the processing apparatus 1 to cause the processing apparatus 1 to perform various processes such as edge trimming processing of the workpiece 100. In Embodiment 1, the control unit 40 includes a computer system. The computer system included in the control unit 50 has an arithmetic processing unit having a microprocessor such as a CPU (Central Processing Unit), a storage device having a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and an input / output interface device. The arithmetic processing unit of the control unit 40 performs arithmetic processing according to a computer program stored in the storage device of the control unit 40, and outputs a control signal for controlling the processing apparatus 1 to each component of the processing apparatus 1 via the input / output interface device of the control unit 40.

[0029] Next, this specification will describe a method for processing a workpiece according to an embodiment with reference to the drawings. FIG. 5 is a cross-sectional view for explaining the holding step 1001 of FIG. 1. FIGS. 6 and 7 are both side cross-sectional views for explaining the first trimming step 1002 of FIG. 1. FIGS. 8 and 9 are both cross-sectional views showing the workpiece 100 after the first trimming step 1002 of FIG. 1 is performed. FIGS. 10 and 11 are both side cross-sectional views for explaining the second trimming step 1003 of FIG. 1. FIG. 12 is a cross-sectional view showing the workpiece 100 after the second trimming step 1003 of FIG. 1 is performed. FIGS. 6 and 10 are both side cross-sectional views in a plane parallel to the vertical direction and the axial direction of the spindle 22. FIGS. 7 and 11 are both side cross-sectional views in a plane orthogonal to the axial direction of the spindle 22.

[0030] The holding step 1001 is a step of holding the second wafer 120 side of the workpiece 100 by the holding surface 11 of the holding table 10 as shown in FIG. 5. In the holding step 1001, for example, the workpiece 100 is conveyed onto the holding surface 11 of the holding table 10 by a conveying unit (not shown), and the central axis of the workpiece 100 (the central axis of the first wafer 110 or the second wafer 120) and the central axis 12 of the holding surface 11 are made to substantially overlap with each other. The second wafer 120 side of the workpiece 100 is oriented toward the holding surface 11 side, and the workpiece 100 is placed thereon, and the second wafer 120 side of the workpiece 100 placed on the holding surface 11 of the holding table 10 is sucked and held.

[0031] The first trimming step 1002 is a step of cutting and removing the peripheral portion on the first wafer 110 side directed upward of the workpiece 100 held in the holding step 1001 while cutting the first cutting blade 21-1 into the peripheral portion on the first wafer 110 side as shown in FIGS. 6 and 7. In the present embodiment, the first trimming step 1002 is performed by the first processing unit 20-1.

[0032] In the first trimming step 1002, first, as shown in FIGS. 6 and 7, the first cutting blade 21-1 mounted at the tip of the first spindle 22-1 is rotated in a rotational direction of cutting from the second wafer 120 side (lower surface) to the first wafer 110 side (upper surface) of the workpiece 100 in front of the relative movement direction of the first cutting blade 21-1 with respect to the workpiece 100, and the first cutting blade 21-1 is cut into the peripheral portion on the first wafer 110 side of the workpiece 100 at a cutting depth 151 shallower than the cutting depth 152 (see FIGS. 10 and 11) in the second trimming step 1003 described later. Hereinafter, the rotational direction of cutting from the second wafer 120 side (lower surface) to the first wafer 110 side (upper surface) of the workpiece 100 in front of the relative movement direction of the first cutting blade 21-1 with respect to the workpiece 100 is appropriately referred to as the up-cut rotational direction.

[0033] In the first trimming step 1002, while rotating the first cutting blade 21-1 in the up-cut rotation direction and making the first cutting blade 21-1 cut into the peripheral portion on the first wafer 110 side of the workpiece 100 at a cutting depth of 151, the holding table 10 that holds the workpiece 100 by the rotation drive unit 35 is rotated around the central axis 12 of the holding surface 11, so that the first cutting blade 21-1 moves the peripheral portion on the first wafer 110 side of the workpiece 100 relative to the workpiece 100 along the circumferential direction of the workpiece 100, and the entire circumference of the peripheral portion on the first wafer 110 side of the workpiece 100 is cut and chamfered in a circular shape, and an annular cut 115 (see FIGS. 8 and 9) with a depth corresponding to the cutting depth of 151 is formed on the entire circumference of the peripheral portion on the first wafer 110 side of the workpiece 100.

[0034] In the first trimming step 1002, in this way, since the first cutting blade 21-1 is rotated in the up-cut rotation direction and the first cutting blade 21-1 is cut into the peripheral portion on the first wafer 110 side, the actual cutting depth 151 becomes shallower than the targeted cutting depth.

[0035] In the first trimming step 1002, in a region where the bonding state between the first wafer 110 and the second wafer 120 via the bonding layer 130 is poor on the outer peripheral side of the workpiece 100, with the cutting of the peripheral portion of the first wafer 110, cracks and chips occur in a region deeper than the depth (corresponding to the cutting depth 151) at which the cut 115 of the peripheral portion of the first wafer 110 is formed, and end material 116 (see FIG. 8) is generated. With the generation of the end material 116, an end face 117 (see FIGS. 8 and 9) is formed on the peripheral portion side of the first wafer 110. In the first trimming step 1002, since the first cutting blade 21-1 is rotated in the up-cut rotation direction to cut and remove the peripheral portion of the first wafer 110, the cutting chips generated at the peripheral portion of the first wafer 110 by cutting and the end material 116 generated along with this cutting can be removed by blowing them upward.

[0036] Conventionally, when the cutting blade is rotated in the up-cut rotation direction and the peripheral portion on the first wafer side is cut deeply all at once, end materials that are too large are generated, and there is a risk that these overly large end materials will collide with the cutting blade, causing uneven wear on the cutting blade. Therefore, in the first trimming step 1002 of the present embodiment, the cutting and removal of the peripheral portion on the first wafer 110 side are performed so that the first cutting blade 21-1 does not cut into the second wafer 120. That is, in the first trimming step 1002, the peripheral portion on the first wafer 110 side is cut and removed at a cutting depth 151 at which the first cutting blade 21-1 does not cut into the second wafer 120. In this way, in the first trimming step 1002, cutting deeply all at once into the peripheral portion on the first wafer 110 side is avoided, so the generation of overly large end materials as in the prior art is suppressed, and the risk of uneven wear occurring on the first cutting blade 21-1 due to the overly large end materials colliding with the first cutting blade 21-1 can be suppressed. In addition, in order to more reliably suppress the possibility of new end materials 116 being generated at the peripheral portion of the first wafer 110 in the second trimming step 1003 that is performed after the first trimming step 1002, it is preferable to set the cutting depth 151 to be sufficiently close to the thickness of the first wafer 110, so that the height remaining at the peripheral portion of the first wafer 110 after the implementation of the first trimming step 1002 is made sufficiently thin.

[0037] As shown in FIGS. 10 and 11, the second trimming step 1003 is a step of cutting and removing the peripheral portion on the first wafer 110 side while cutting the second cutting blade 21-2 at a predetermined cutting depth 152 deeper than the cutting depth 151 of the first trimming step 1002, from the first wafer 110 side of the workpiece 100 held in the holding step 1001 after the first trimming step 1002. In the present embodiment, the second trimming step 1003 is performed by the second processing unit 20-2.

[0038] In the second trimming step 1003, first, as shown in FIGS. 10 and 11, the second cutting blade 21-2 mounted at the tip of the second spindle 22-2 is rotated in the cutting direction from the first wafer 110 side (upper surface) to the second wafer 120 side (lower surface) of the workpiece 100 in front of the relative movement direction of the second cutting blade 21-2 with respect to the workpiece 100, and the second cutting blade 21-2 is cut into the peripheral portion on the first wafer 110 side of the workpiece 100 at a predetermined cutting depth 152 deeper than the cutting depth 151 of the first trimming step 1002. Hereinafter, the rotation direction in which the second cutting blade 21-2 cuts from the first wafer 110 side (upper surface) to the second wafer 120 side (lower surface) of the workpiece 100 in front of the relative movement direction of the second cutting blade 21-2 with respect to the workpiece 100 is appropriately referred to as the down-cut rotation direction.

[0039] In the second trimming step 1003, while rotating the second cutting blade 21-2 in the down-cut rotation direction and with the second cutting blade 21-2 cut into the peripheral portion on the first wafer 110 side of the workpiece 100 at the cutting depth 152, the holding table 10 that holds the workpiece 100 by the rotation drive unit 35 is rotated around the central axis 12 of the holding surface 11, so that the second cutting blade 21-2 is relatively moved with respect to the workpiece 100 along the circumferential direction of the workpiece 100 for the peripheral portion on the first wafer 110 side of the workpiece 100, and the entire circumference of the peripheral portion on the first wafer 110 side of the workpiece 100 is cut and chamfered in an annular shape deeper than the cut 115 formed in the first trimming step 1002, and an annular cut 118 (see FIG. 12) having a depth corresponding to the predetermined cutting depth 152 is formed in the entire circumference of the peripheral portion on the first wafer 110 side of the workpiece 100.

[0040] In the second trimming step 1003, as described above, since the second cutting blade 21-2 is rotated in the down-cut rotation direction and the second cutting blade 21-2 is cut into the peripheral portion on the side of the first wafer 110, the actual cutting depth 152 can be formed to the targeted cutting depth. For this reason, the predetermined cutting depth 152 can be set according to the targeted depth of the cut 118 formed in the peripheral portion of the workpiece 100.

[0041] In the first trimming step 1002 performed before the implementation of the second trimming step 1003, the end material 116 (see FIG. 8) generated in a region deeper than the depth at which the cut 115 of the peripheral portion of the first wafer 110 is formed (corresponding to the cutting depth 151) is removed so as to be blown upward. For this reason, in the second trimming step 1003, since the generation of new end material 116 at the peripheral portion of the first wafer 110 is suppressed, even though the second cutting blade 21-2 is rotated in the down-cut rotation direction to cut and remove the peripheral portion of the first wafer 110, the possibility of pressing the end material 116 and cutting chips generated in the upper first wafer 110 against the second wafer 120 located below the workpiece 100 can be suppressed. Thereby, the possibility of cracks occurring in the second wafer 120 can be suppressed.

[0042] Note that in the second trimming step 1003, in the example of the present embodiment shown in FIGS. 10 and 11, an annular cut 118 reaching the depth at which the bonding layer 130 is formed is formed by cutting the second cutting blade 21-2 to the depth at which the bonding layer 130 is formed. However, the present invention is not limited to this, and the second cutting blade 21-2 may be cut into the second wafer 120. In this case, an annular cut 118 reaching the second wafer 120 can be formed.

[0043] Also, in the present embodiment, by providing the first processing unit 20-1 and the second processing unit 20-2, a processing apparatus 1 having two spindles (the first spindle 22-1 and the second spindle 22-2) is used, and in the first trimming step 1002, cutting is performed by the first cutting blade 21-1 of the first processing unit 20-1, and in the second trimming step 1003, cutting is performed by the second cutting blade 21-2 of the second processing unit 20-2. However, the present invention is not limited to this. By providing only one processing unit 20, a processing apparatus having one spindle is used, and in the first trimming step 1002 and the second trimming step 1003, cutting may be performed by the same cutting blade 21.

[0044] Also, in the present embodiment, in the first trimming step 1002 and the second trimming step 1003, by rotating the holding table 10 that holds the workpiece 100 around the central axis 12 of the holding surface 11, each of the first spindle 22-1 and the second cutting blade 21-2 is relatively moved along the circumferential direction of the workpiece 100 with respect to the workpiece 100 to the peripheral portion on the first wafer 110 side of the workpiece 100. However, the present invention is not limited to this, and each of the first spindle 22-1 and the second cutting blade 21-2 may be rotationally moved around the central axis 12 of the holding surface 11.

[0045] In the processing method of the workpiece according to the embodiment having the above configuration, in the first trimming step 1002, the first cutting blade 21-1 is rotated in the up-cut rotation direction to cut and remove the peripheral portion of the first wafer 110. Therefore, in a region where the bonding state between the first wafer 110 and the second wafer 120 via the bonding layer 130 is poor on the outer peripheral side of the workpiece 100, the end material 116 generated can be removed by blowing it upward. As a result, in the second trimming step 1003 performed after the first trimming step 1002, the generation of new end material 116 at the peripheral portion of the first wafer 110 can be suppressed. Thus, in the second trimming step 1003, even though the second cutting blade 21-2 is rotated in the down-cut rotation direction to cut and remove the peripheral portion of the first wafer 110, the risk of pressing the end material 116 and cutting chips generated in the upper first wafer 110 against the second wafer 120 on the lower side of the workpiece 100 can be suppressed. Thereby, the risk of cracking in the second wafer 120 can be suppressed. Further, in the processing method of the workpiece according to the embodiment, in the second trimming step 1003, the second cutting blade 21-2 is rotated in the down-cut rotation direction to cut and remove the peripheral portion of the first wafer 110, so that an annular cut 118 with a targeted cut depth can be formed. In this way, the processing method of the workpiece according to the embodiment has the effect of reducing the risk of cracking in the second wafer 120 and being able to remove at the targeted cut depth when removing the peripheral portion on the first wafer 110 side of the workpiece 100 in which the first wafer 110 and the second wafer 120 are bonded via the bonding layer 130.

[0046] Further, in the processing method of the workpiece according to the embodiment, the first cutting blade 21-1 in the first trimming step 1002 does not cut into the second wafer 120. For this reason, conventionally, when the cutting blade is rotated in the up-cut rotation direction and the peripheral portion on the first wafer side is cut deeply at once, extremely large end materials are generated, and there is a problem that the extremely large end materials may collide with the cutting blade and cause uneven wear on the cutting blade. Therefore, in the first trimming step 1002 of the processing method of the workpiece according to the embodiment, in order to perform cutting and removal of the peripheral portion on the first wafer 110 side so that the first cutting blade 21-1 does not cut into the second wafer 120, cutting deeply into the peripheral portion on the first wafer 110 side at once in the first trimming step 1002 is avoided. As a result, generation of extremely large end materials as in the prior art is suppressed, and the risk that uneven wear occurs on the first cutting blade 21-1 due to the extremely large end materials colliding with the first cutting blade 21-1 can be suppressed.

[0047] Conventionally, particularly when the abrasive grains of the cutting blade are 5 μm or more and less than 30 μm in diameter, when the cutting blade rotates from the lower surface to the upper surface of the workpiece in the forward direction of the movement direction of the workpiece and cuts into the workpiece, the cutting blade has difficulty biting into the first wafer, cannot cut the first wafer, and escapes upward, so there has been a problem that a cut shallower than the target cutting depth is likely to be formed. Therefore, in the method for machining a workpiece according to the embodiment, in the first trimming step 1002 in which the first cutting blade 21-1 may cut the first wafer 110 shallower than the target cutting depth, before the second trimming step 1003 is performed, the generated end material 116 is removed so as to be blown upward, and then, in the second trimming step 1003 in which the second cutting blade 21-2 can cut the first wafer 110 at the target cutting depth, the cutting depth is adjusted to match the target cutting depth 152. Therefore, particularly when the abrasive grains of at least one of the first cutting blade 21-1 and the second cutting blade 21-2 have a particle size of 5 μm or more and less than 30 μm, the effect of suppressing the risk of forming a cut shallower than the target cutting depth can be achieved.

[0048] Note that the present invention is not limited to the above embodiment. That is, various modifications can be made and implemented without departing from the gist of the present invention.

Explanation of reference numerals

[0049] 10 Holding table 11 Holding surface 21 Cutting blade 21-1 First cutting blade 21-2 Second cutting blade 100 Workpiece 110 First wafer 120 Second wafer 130 Bonding layer 151, 152 Cutting depth 1001 Holding step 1002 First trimming step 1003 Second trimming step

Claims

1. A method for processing a workpiece, which removes a peripheral portion on the first wafer side of a workpiece obtained by bonding a first wafer and a second wafer via a bonding layer, comprising: a holding step of holding the second wafer side of the workpiece on a holding surface of a holding table; a first trimming step of cutting and removing the peripheral portion while cutting a first cutting blade into the peripheral portion on the first wafer side of the workpiece held in the holding step; after the first trimming step, a second trimming step of cutting and removing the peripheral portion while cutting a second cutting blade into the first wafer side of the workpiece held in the holding step at a predetermined cutting depth deeper than the cutting depth of the first trimming step; in the first trimming step, the first cutting blade is rotated in a rotational direction of cutting from the second wafer side of the workpiece toward the first wafer side; in the second trimming step, the second cutting blade is rotated in a rotational direction of cutting from the first wafer side of the workpiece toward the second wafer side.

2. The method for processing a workpiece according to claim 1, wherein the first cutting blade in the first trimming step does not cut into the second wafer.

3. The method for processing a workpiece according to claim 1 or claim 2, wherein abrasive grains of at least one of the first cutting blade and the second cutting blade have an abrasive grain size smaller than 30 μm.

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