WORKPIECE PROCESSING METHOD

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2024-001213 filed in Japan on Jan. 9, 2024.

BACKGROUND

The present disclosure relates to a workpiece processing method of removing a peripheral edge portion on a first wafer side of a workpiece obtained by bonding a first wafer and a second wafer via a bonding layer.

Grinding a back surface of a wafer (workpiece) having a chamfered peripheral edge portion will form the peripheral edge portion with an acute angle, and this portion might cause occurrence of a crack or a chip. Therefore, before grinding, edge trimming is performed in which a part or all of the chamfered portion is cut and removed by a cutting blade along an outer periphery of the workpiece (refer to, for example, JP 2010-245167 A).

Conventional edge trimming includes a procedure referred to as down-cutting of allowing a cutting blade to make a cut into the workpiece while rotating in a direction from an upper surface to a lower surface of the workpiece in front of the workpiece in a moving direction. When edge trimming is performed in this manner on the workpiece in which the first wafer and the second wafer are bonded via the bonding layer, there is a problem that a crack occurs in the second wafer by pressing end materials (cutting particles) generated in the first wafer in the upper side against the second wafer on the lower side of the workpiece. In particular, when the bonding region on the outer peripheral side of the workpiece has an unsatisfactory bonding status, the outer peripheral region of the first wafer is likely to peel off, leading to occurrence of large end materials (cutting particles) and occurrence of cracks in the second wafer.

To handle this, there is a conceivable procedure referred to as up-cutting of allowing the cutting blade to make a cut into the workpiece while rotating in a direction from the lower surface to the upper surface of the workpiece in front of the workpiece in a moving direction. However, when cutting the peripheral edge portion of the first wafer by up-cutting, the cutting blade is less likely to bite into the first wafer as compared with down-cutting. Therefore, the cutting blade fails to cut the first wafer and escapes upward, so as to make a cut at a depth shallower than the target cut depth, leading to a problem that the peripheral edge portion of the first wafer is finished thick.

SUMMARY

A workpiece processing method according to one aspect of the present disclosure is of removing a peripheral edge portion on a first wafer side of a workpiece obtained by bonding a first wafer and a second wafer via a bonding layer. The workpiece processing method includes: 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 edge portion of the workpiece on the first wafer side while allowing a first cutting blade to cut into the peripheral edge portion of the workpiece held in the holding step; and a second trimming step of, after the first trimming step, cutting and removing the peripheral edge while allowing a second cutting blade to cut into the peripheral edge portion from the first wafer side of the workpiece held in the holding step at a predetermined cut depth deeper than the cut depth of the first trimming step. The first trimming step includes rotating the first cutting blade in a rotation direction of cutting the workpiece from the second wafer side toward the first wafer side. The second trimming step includes rotating the second cutting blade in a rotation direction of cutting the workpiece from the first wafer side toward the second wafer side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a handling procedure of a workpiece processing method according to an embodiment;

FIG. 2 is a perspective view illustrating a configuration example of a workpiece to be processed by the workpiece processing method according to the embodiment;

FIG. 3 is a cross-sectional view illustrating the workpiece of FIG. 2;

FIG. 4 is a perspective view illustrating a configuration example of a processing apparatus that performs the workpiece processing method according to the embodiment;

FIG. 5 is a cross-sectional view illustrating a holding step in FIG. 1;

FIG. 6 is a side sectional view illustrating a first trimming step in FIG. 1;

FIG. 7 is a side sectional view illustrating the first trimming step in FIG. 1;

FIG. 8 is a cross-sectional view illustrating the workpiece after the first trimming step in FIG. 1;

FIG. 9 is a cross-sectional view illustrating the workpiece after the first trimming step in FIG. 1;

FIG. 10 is a side sectional view illustrating a second trimming step in FIG. 1;

FIG. 11 is a side sectional view illustrating the second trimming step in FIG. 1; and

FIG. 12 is a cross-sectional view illustrating the workpiece after the second trimming step in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present disclosure will be described in detail with reference to the drawings. The present invention is not limited by the description in the following embodiments. In addition, the constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined with each other. In addition, various omissions, substitutions, or alterations in the configuration can be made without departing from the scope and spirits of the present invention.

Embodiment

A workpiece processing method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart illustrating a handling procedure of the workpiece processing method according to the embodiment. As illustrated in FIG. 1, the workpiece processing method according to the embodiment includes a holding step 1001, a first trimming step 1002, and a second trimming step 1003. The workpiece processing method according to the embodiment is a method of removing a peripheral edge portion on the first wafer 110 side of a workpiece 100 (refer to FIGS. 2 and 3) obtained by bonding a first wafer 110 and a second wafer 120 to be described below via a bonding layer 130.

FIG. 2 is a perspective view illustrating a configuration example of the workpiece 100 to be processed by the workpiece processing method according to the embodiment. FIG. 3 is a cross-sectional view illustrating the workpiece 100 of FIG. 2. As illustrated in FIGS. 2 and 3, the workpiece 100 to be processed by the workpiece processing method according to the embodiment is a wafer referred to as a stacked wafer including the first wafer 110, the second wafer 120, and the bonding layer 130 that bonds the first wafer 110 and the second wafer 120 with each other.

The first wafer 110 and the second wafer 120 each are, for example, a wafer such as a disc-shaped semiconductor device wafer or an optical device wafer using a material such as silicon, sapphire, silicon carbide (SiC), and gallium arsenide as a base material. As illustrated in FIG. 3, the peripheral edge portion of each of the first wafer 110 and the second wafer 120 is chamfered over the entire circumference. The first wafer 110 and the second wafer 120 may be the same wafer or different wafers. The first wafer 110 and the second wafer 120, with their central axes aligned with each other, are stacked with each other via the bonding layer 130, and are bonded with each other by the bonding layer 130 to constitute the workpiece 100.

In the present embodiment, the first wafer 110 and the second wafer 120 include a plurality of planned division lines formed in a lattice shape on a flat front surface, and include devices (devices 140 in the example illustrated in FIG. 2) formed in a region partitioned by the planned division lines. As illustrated in FIG. 2, in the workpiece 100 of the present embodiment, a front surface side of the first wafer 110, on which the devices 140 are formed, is bonded to the second wafer 120 via the bonding layer 130. In the workpiece 100, a back surface of the first wafer 110, being the side opposite to the front surface side of the first wafer 110 including the devices 140, is provided as an exposed surface. This exposed surface is a surface to be ground after the workpiece processing method according to the embodiment is performed and the peripheral edge portion is removed. The first wafer 110 and the second wafer 120 are not limited to the form including the devices 140 formed as in the present invention, and the devices 140 may be omitted from one or both of the first wafer 110 and the second wafer 120.

Examples of the bonding layer 130 include a resin adhesive such as benzocyclobutene, a silicon oxide (SiO₂) layer, a first active layer formed by performing a surface activation treatment on a bonding surface of the first wafer 110 to be bonded to the second wafer 120, and a second active layer formed by performing a surface activation treatment on a bonding surface of the second wafer 120 to be bonded to the first wafer 110. When the first wafer 110 or the second wafer 120 uses silicon as a base material, the bonding layer 130 may be a silicon oxide film layer formed on the bonding surface of the first wafer 110 or the second wafer 120.

FIG. 4 is a perspective view illustrating a configuration example of a processing apparatus 1 that performs the workpiece processing method according to the embodiment. As illustrated in FIG. 4, the processing apparatus 1 that implements the workpiece processing method according to the 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 rotary drive unit 35, and a control unit 40.

As illustrated in FIG. 4, the holding table 10 is a table referred to as a chuck table including: a disc-shaped frame body having a recess; and a disc-shaped suction portion fitted in the recess. The suction portion of the holding table 10 is formed of a material such as porous ceramic having a large number of porous holes, and is connected to a vacuum suction source (not illustrated) via a vacuum suction path (not illustrated). 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 which sucks and holds the placed workpiece 100 by a negative pressure introduced from a vacuum suction source. The holding surface 11 and the upper surface of the frame body of the holding table 10 are disposed on an identical plane and formed in parallel to the XY plane which is a horizontal plane. The holding table 10 is movable in the X-axis direction parallel to the horizontal direction by the X-axis direction moving unit 31. The holding table 10 has a rotary drive unit 35 below the frame body and the suction portion, and can freely rotate (rotatable), by the rotary drive unit 35, about a central axis 12 (refer to diagrams such as FIG. 6) passing through the center of the holding surface 11 and parallel to the Z-axis direction being parallel to the vertical direction.

In the present embodiment, as illustrated 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, in a case where each part related to the first processing unit 20-1 is distinguished from each part related to the second processing unit 20-2, the reference numeral will be followed by “-1”; and in a case where each part related to the second processing unit 20-2 is distinguished from each part related to the first processing unit 20-1, the reference numeral is followed by “-2” for distinction. When there is no need to distinguish the first processing unit 20-1 and the second processing unit 20-2 from each other, the corresponding parts are assumed to be common to the two units, and the reference numeral will be appropriately omitted, with no additions of “-1” or “-2”. In addition, when describing parts having the same configuration or when not particularly distinguished in the first processing unit 20-1 and the second processing unit 20-2, the unit will be simply denoted as the processing unit 20.

As illustrated in FIG. 4, the processing unit 20 includes a cutting blade 21 and a spindle 22. The cutting blade 21 is attached to a tip of the spindle 22 and is rotated by the spindle 22 being a rotation axis so as to perform cutting work on the workpiece 100 held on the holding table 10. In a first embodiment, the cutting blade 21 is a cutting grindstone having an annular cutting edge in which abrasives made of a material such as diamond or cubic boron nitride (CBN) are fixed with a bond (bonding material) such as metal or resin and formed to have a predetermined thickness. The cutting blade 21 may be a hubless blade or a hub blade in which an annular cutting blade is fixed to the outer periphery of an annular base.

The spindle 22 is rotatable about an axis parallel to the horizontal direction and parallel to the Y-axis direction orthogonal to the X-axis direction, and is rotated about the axis by a motor (not illustrated) joined to the spindle 22. The spindle 22 supports the cutting blade 21 in a rotatable manner attached to the tip of the spindle 22 about the axis parallel to the Y-axis direction.

That is, in the example of the present embodiment illustrated in FIG. 4, the first processing unit 20-1 of the processing unit 20 includes a first spindle 22-1 whose tip faces the −Y direction and a first cutting blade 21-1 fixed to the tip of the first spindle 22-1 and rotatable with the first spindle 22-1; the second processing unit 20-2 of the processing unit 20 includes a second spindle 22-2 whose tip faces the +Y direction and a second cutting blade 21-2 fixed to the tip of the second spindle 22-2 and rotatable with the second spindle 22-2.

In the present embodiment, the abrasives of at least one of the cutting blades 21, namely, one of the first cutting blade 21-1 or the second cutting blade 21-2, that is, the abrasives fixed with the bonding material in the cutting blade 21 preferably have a grain size of #700 (No. 700) or more and #2000 (No. 2000) or less. Here, the grain size of the abrasives of the cutting blade 21 is defined by JIS standard “R 6001: Bonded abrasives—Determination and designation of grain size distribution”, and is a parameter. In this parameter, the larger the central grain size, the smaller the number; the smaller the central grain size, the larger the number. When the grain size is converted into the grain diameter (abrasive diameter) of the abrasives based on this definition, it is preferable, in the present embodiment, that the abrasives of the cutting blade 21 of at least one of the first cutting blade 21-1 or the second cutting blade 21-2 have an abrasive diameter of 5 μm or more and less than 30 μm. In the present invention, both the abrasives of the first cutting blade 21-1 and the abrasives of the second cutting blade 21-2 may have an abrasive diameter of 5 μm or more and less than 30 μm.

The first processing unit 20-1 is movable in the Y-axis direction and the Z-axis direction by the Y-axis direction moving unit 32 and the Z-axis direction moving unit 33, respectively, independently of the second processing unit 20-2. The second processing unit 20-2 is provided to be movable in the Y-axis direction and the Z-axis direction by the Y-axis direction moving unit 32 and the Z-axis direction moving unit 33, respectively, independently of the first processing unit 20-1. In this manner, the processing apparatus 1 is a processing apparatus including two sets of the first processing unit 20-1 and the second processing unit 20-2, that is an apparatus also referred to as a two-spindle dicer, or a facing dual-type processing apparatus.

The X-axis direction moving unit 31 moves the holding table 10 in the X-axis direction relative to the processing units 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) in the Y-axis direction and the Z-axis direction respectively, relative to the holding table 10. The rotary drive unit 35 rotates the holding table 10 relative to the processing units 20 (the first processing unit 20-1 and the second processing unit 20-2) about the central axis 12 of the holding surface 11.

Under the control of the control unit 40 and in a state where the cutting blade 21 is positioned at a position facing the peripheral edge portion of the workpiece 100 held on the holding table 10 in the vertical direction, and in a state where the cutting blade 21 to which the rotating operation about the axis parallel to the Y-axis direction is applied is cut into the peripheral edge portion of the workpiece 100 at a predetermined cutting depth from a surface facing upward by the rotating operation of the spindle 22, the processing unit 20 rotates the holding table 10 holding the workpiece 100 about the central axis 12 of the holding surface 11 by the rotary drive unit 35 so as to perform processing referred to as edge trimming processing of cutting the entire circumference of the peripheral edge portion of the workpiece 100 annularly to be chamfered.

The control unit 40 controls operations of various components of the processing apparatus 1 to cause the processing apparatus 1 to perform various types of processing such as edge trimming processing of the workpiece 100. The control unit 40 includes a computer system in the first embodiment. The computer system included in the control unit 40 includes an arithmetic processing apparatus having a microprocessor such as a central processing unit (CPU), a storage apparatus having memory such as Read Only Memory (ROM) or Random Access Memory (RAM), and an input/output interface apparatus. The arithmetic processing apparatus of the control unit 40 performs arithmetic processing according to a computer program stored in the storage apparatus 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 apparatus of the control unit 40.

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

As illustrated in FIG. 5, the holding step 1001 is a step of holding the workpiece 100 on the second wafer 120 side on the holding surface 11 of the holding table 10. In the holding step 1001, for example, the workpiece 100 is transferred onto the holding surface 11 of the holding table 10 by a transfer unit (not illustrated), and then, the workpiece 100 is placed with the second wafer 120 side of the workpiece 100 facing the holding surface 11 side so that 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 substantially aligned with each other. Subsequently, the second wafer 120 side of the workpiece 100 placed on the holding surface 11 of the holding table 10 is sucked and held.

As illustrated in FIGS. 6 and 7, the first trimming step 1002 is a step of cutting and removing the peripheral edge portion on the first wafer 110 side while making a cut, with the first cutting blade 21-1, into the peripheral edge portion on the first wafer 110 side facing the upper direction of the workpiece 100 held in the holding step 1001. In the present embodiment, the first trimming step 1002 is performed by the first processing unit 20-1.

In the first trimming step 1002, first, as illustrated in FIGS. 6 and 7, the first cutting blade 21-1 attached to the tip of the first spindle 22-1 is rotated in a rotation direction in which cutting is performed from the second wafer 120 side (lower surface) toward the first wafer 110 side (upper surface) of the workpiece 100 in front of the first cutting blade 21-1 in the moving direction relative to the workpiece 100, and then, a cut is made into a peripheral edge portion of the workpiece 100 on the first wafer 110 side by the first cutting blade 21-1 at a cut depth 151 shallower than a cut depth 152 (refer to FIGS. 10 and 11) in the second trimming step 1003 described below. Hereinafter, the rotation direction in which cutting is performed from the second wafer 120 side (lower surface) toward the first wafer 110 side (upper surface) of the workpiece 100 in front of the moving direction of the first cutting blade 21-1 relative to the workpiece 100 is appropriately referred to as an up-cut rotation direction.

In the first trimming step 1002, while the first cutting blade 21-1 is rotated in the up-cut rotation direction in a state where a cut is made with the first cutting blade 21-1 into the peripheral edge portion of the workpiece 100 on the first wafer 110 side at the cut depth 151, the holding table 10 that holds the workpiece 100 is rotated about the central axis 12 of the holding surface 11 by the rotary drive unit 35. With this procedure, the first cutting blade 21-1 is moved along the peripheral edge portion of the workpiece 100 on the first wafer 110 side relative to the workpiece 100 in the circumferential direction of the workpiece 100 so as to annularly cut and chamfer the entire circumference of the peripheral edge portion of the workpiece 100 on the first wafer 110 side. This leads to formation of a cut 115 (refer to FIGS. 8 and 9) having a depth equivalent to the cut depth 151 on the entire circumference of the peripheral edge portion of the workpiece 100 on the first wafer 110 side.

In the first trimming step 1002, the first cutting blade 21-1 is rotated in the up-cut rotation direction to allow the first cutting blade 21-1 to make a cut into the peripheral edge portion on the first wafer 110 side in this manner, the actual cut depth 151 is to be shallower than the target cut depth.

In the first trimming step 1002, in a region of an unsatisfactory bonding status between the first wafer 110 and the second wafer 120 via the bonding layer 130 on the outer peripheral side of the workpiece 100, there occurs a crack or a chip in a region deeper than the depth (equivalent to the cut depth 151) at which the cut 115 is formed in the peripheral edge portion of the first wafer 110, occurring with the cutting of the peripheral edge portion of the first wafer 110, causing generation of an end material 116 (refer to FIG. 8). The generation of the end material 116 leads to generation of an end surface 117 (refer to FIGS. 8 and 9) formed on the peripheral edge portion side of the first wafer 110. 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 edge portion of the first wafer 110, making it possible to perform upward blow to remove cutting particles generated in the peripheral edge portion of the first wafer 110 due to the cutting and the end material 116 generated with this cutting.

In a conventional method, making a cut into the peripheral edge portion on the first wafer side deep in a single cutting motion while rotating the cutting blade in the up-cut rotation direction would generate an excessively large end material. This excessively large end material would collide with the cutting blade to cause occurrence of uneven wear in the cutting blade. To handle this, the first trimming step 1002 of the present embodiment performs cutting and removal of the peripheral edge portion on the first wafer 110 side so as not to allow the first cutting blade 21-1 to cut into the second wafer 120. That is, the first trimming step 1002 performs cut and removal of the peripheral edge portion on the first wafer 110 side at the cut depth 151 at which the first cutting blade 21-1 does not cut into the second wafer 120. In this manner, the first trimming step 1002 can avoid cutting of the peripheral edge portion on the first wafer 110 side deep in a single cutting motion, making possible to suppress generation of an excessively large end material as in conventional techniques and to suppress the risk of occurrence of uneven wear in the first cutting blade 21-1 due to collision of the excessively large end material with the first cutting blade 21-1. In order to more reliably suppress the risk of generation of new end materials 116 in the peripheral edge portion of the first wafer 110 in the second trimming step 1003 following the first trimming step 1002, it is preferable to set the cut depth 151 sufficiently close to the thickness of the first wafer 110 to sufficiently reduce the height remaining in the peripheral edge portion of the first wafer 110 after the first trimming step 1002.

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

In the second trimming step 1003, first, as illustrated in FIGS. 10 and 11, the second cutting blade 21-2 attached to the tip of the second spindle 22-2 is rotated in a rotation direction of cutting from the first wafer 110 side (upper surface) toward the second wafer 120 side (lower surface) of the workpiece 100 in front of the second cutting blade 21-2 in the moving direction relative to the workpiece 100, and then, a cut is made into the peripheral edge portion of the workpiece 100 on the first wafer 110 side by the second cutting blade 21-2 at a predetermined cut depth 152 deeper than the cut depth 151 of the first trimming step 1002. Hereinafter, the rotation direction in which cutting is performed from the first wafer 110 side (upper surface) toward the second wafer 120 side (lower surface) of the workpiece 100 in front of the moving direction of the second cutting blade 21-2 relative to the workpiece 100 is appropriately referred to as a down-cut rotation direction.

In the second trimming step 1003, while the second cutting blade 21-2 is rotated in the down-cut rotation direction in a state where a cut is made with the second cutting blade 21-2 into the peripheral edge portion of the workpiece 100 on the first wafer 110 side at the cut depth 152, the holding table 10 that holds the workpiece 100 is rotated about the central axis 12 of the holding surface 11 by the rotary drive unit 35. With this procedure, the second cutting blade 21-2 is moved along the peripheral edge portion of the workpiece 100 on the first wafer 110 side relative to the workpiece 100 in the circumferential direction of the workpiece 100 so as to annularly cut and chamfer the entire circumference of the peripheral edge portion of the workpiece 100 on the first wafer 110 side at a depth further deeper than the cut 115 formed in the first trimming step 1002. This leads to formation of a cut 118 (refer to FIG. 12) having a depth equivalent to a predetermined cut depth 152 on the entire circumference of the peripheral edge portion of the workpiece 100 on the first wafer 110 side.

In the second trimming step 1003, the second cutting blade 21-2 is rotated in the down-cut rotation direction to allow the second cutting blade 21-2 to make a cut into the peripheral edge portion on the first wafer 110 side in this manner, making it possible to form the actual cut depth 152 to be at the target cut depth. Therefore, the predetermined cut depth 152 can be set according to a target depth of the cut 118 formed in the peripheral edge portion of the workpiece 100.

In the first trimming step 1002 performed before the second trimming step 1003, the end material 116 (refer to FIG. 8) generated in the region deeper than the depth (corresponding to the cut depth 151) at which the cut 115 is formed in the peripheral edge portion of the first wafer 110 is removed so as to be blown upward. This suppresses generation of new end materials 116 in the peripheral edge portion of the first wafer 110 in the second trimming step 1003. With this procedure, it is possible to suppress the possibility of pressing the end material 116 and cutting particles generated in the upper first wafer 110 against the second wafer 120 coming in contact with the lower side of the workpiece 100 even though the peripheral edge portion of the first wafer 110 is cut and removed by rotating the second cutting blade 21-2 in the down-cut rotation direction, leading to suppression of the risk of occurrence of a crack in the second wafer 120.

In the example of the present embodiment illustrated in FIGS. 10 and 11, the second trimming step 1003 allows the second cutting blade 21-2 to cut to the depth of the bonding layer 130 to form the annular cut 118 to the depth of the bonding layer 130. The present invention is not limited thereto, and the second cutting blade 21-2 may be allowed to cut into the second wafer 120, and in this case, the annular cut 118 can be formed to reach the second wafer 120.

Moreover, in the present embodiment, the first processing unit 20-1 and the second processing unit 20-2 are provided, and accordingly, the processing apparatus 1 equipped with the 2-axis spindle 22 (including the first spindle 22-1 and the second spindle 22-2) is used to perform cutting by the first cutting blade 21-1 of the first processing unit 20-1 in the first trimming step 1002 and cutting is performed by the second cutting blade 21-2 of the second processing unit 20-2 in the second trimming step 1003. However, the present invention is not limited thereto, and only one processing unit 20 may be provided, and the processing apparatus equipped with a 1-axis spindle 22 may be used to perform the cutting by the same cutting blade 21 in the first trimming step 1002 and the second trimming step 1003.

In the present embodiment, in the first trimming step 1002 and the second trimming step 1003, the holding table 10 holding the workpiece 100 is rotated about the central axis 12 of the holding surface 11 so as to move the first spindle 22-1 and the second cutting blade 21-2 along the peripheral edge portion of the workpiece 100 on the first wafer 110 side of the workpiece 100 in the circumferential direction of the workpiece 100 relative to the workpiece 100. However, the present invention is not limited thereto, and the first spindle 22-1 and the second cutting blade 21-2 may be rotationally moved about the central axis 12 of the holding surface 11 individually.

The workpiece processing method according to the embodiment having the above-described configuration includes the first trimming step 1002 to rotate the first cutting blade 21-1 in the up-cut rotation direction to cut and remove the peripheral edge portion of the first wafer 110. This makes it possible to blow upward and remove the end material 116 generated in the region of an unsatisfactory bonding status between the first wafer 110 and the second wafer 120 via the bonding layer 130 on the outer peripheral side of the workpiece 100. This makes it possible to suppress generation of new end materials 116 at the peripheral edge portion of the first wafer 110 in the second trimming step 1003 performed after the first trimming step 1002. Therefore, in the second trimming step 1003, it is possible to suppress the risk of pressing the end material 116 and the cutting particles generated in the upper first wafer 110 against the second wafer 120 on the lower side of the workpiece 100 even though the peripheral edge portion of the first wafer 110 is cut and removed by rotating the second cutting blade 21-2 in the down-cut rotation direction, leading to suppression of the risk of occurrence of a crack in the second wafer 120. Furthermore, the workpiece processing method according to the embodiment includes the second trimming step 1003 to rotate the second cutting blade 21-2 in the down-cut rotation direction to cut and remove the peripheral edge portion of the first wafer 110, making it possible to form the annular cut 118 having a targeted cut depth. In this manner, the workpiece processing method according to the embodiment has an effect of lowering the risk of occurrence of a crack in the second wafer 120 when removing the peripheral edge portion on the first wafer 110 side of the workpiece 100 obtained by bonding the first wafer 110 and the second wafer 120 to each other via the bonding layer 130, and an effect of successfully removing the peripheral edge portion at a targeted cut depth.

In the workpiece processing method according to the embodiment, the first cutting blade 21-1 in the first trimming step 1002 does not cut into the second wafer 120. In a conventional method, making a cut into the peripheral edge portion on the first wafer side deep in a single cutting motion while rotating the cutting blade in the up-cut rotation direction would generate an excessively large end material. This excessively large end material would collide with the cutting blade to cause a problem of occurrence of uneven wear in the cutting blade. To handle this, the workpiece processing method according to the embodiment includes the first trimming step 1002 to cut and remove the peripheral edge portion on the first wafer 110 side so that the first cutting blade 21-1 does not cut into the second wafer 120. This avoids the situation in which the peripheral edge portion on the first wafer 110 side is cut deep in a single cutting motion in the first trimming step 1002. This makes it possible to suppress generation of an excessively large end material as in the conventional technique, leading to suppression of the risk of occurrence of uneven wear in the first cutting blade 21-1 due to collision of the excessively large end material with the first cutting blade 21-1.

There has been a conventional problem, occurring particularly when the abrasives of the cutting blade have an abrasive diameter of 5 μm or more and less than 30 μm, that allowing the cutting blade to cut into the workpiece while rotating the cutting blade in a direction from the lower surface to the upper surface of the workpiece in front of the moving direction of the workpiece would have difficulty in letting the cutting blade to bite into the first wafer. Therefore, the cutting blade fails to cut the first wafer and escapes upward, leading to formation of a cut at a depth shallower than the target cut depth at high likelihood. To handle this, the workpiece processing method according to the embodiment similarly includes the first trimming step 1002 in which the first cutting blade 21-1 might cut into the first wafer 110 at a depth shallower than the target cut depth to remove the end material 116 to be blown upward before the second trimming step 1003. Thereafter, in the second trimming step 1003 in which the second cutting blade 21-2 can cut into the first wafer 110 at the target cut depth, the cut depth 152 is finely tuned to the target cut depth. Therefore, particularly when the abrasive diameter of at least one of the cutting blades 21, namely, one of the first cutting blade 21-1 and the second cutting blade 21-2, is 5 μm or more and less than 30 μm, there is an effect of suppressing the risk of forming a cut at a depth shallower than the target cut depth.

According to the present disclosure, the first trimming step is provided to perform cutting and removal of the peripheral edge portion of the first wafer by rotating the first cutting blade in the rotation direction of cutting the workpiece from the second wafer side toward the first wafer side in front of the first cutting blade in the moving direction relative to the workpiece, and the second trimming step is provided to perform cutting and removal of the peripheral edge portion of the first wafer by rotating the second cutting blade in the rotation direction of cutting the workpiece from the first wafer side toward the second wafer side in front of the second cutting blade in the moving direction relative to the workpiece. With this configuration, when removing the peripheral edge portion on the first wafer side of the workpiece obtained by bonding the first wafer and the second wafer via the bonding layer, it is possible to lower the risk of occurrence of a crack in the second wafer and possible to remove the peripheral edge portion at a target cut depth.

Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.

WORKPIECE PROCESSING METHOD

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