Processing method of laminate wafer

Abstract

To provide a processing method of a laminate wafer, capable of grinding the laminate wafer to reduce its thickness without deteriorating its quality.SOLUTION: A processing method of a laminate wafer is a processing method of a laminate wafer in which a front surface side of a first wafer of which an outer peripheral edge is beveled in a circular arc shape and a front surface side of a second wafer are bonded, and comprises: a beveling part removing step 103 of applying an external force to a beveling part of the first wafer to separate the beveling part from the first wafer, and thereby removing the beveling part; and a grinding step 104 of grinding a back surface side on the side opposite to the front surface side of the first wafer after the beveling part removing step 103.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for processing a laminated wafer.

Background Art

[0002] In recent years, in order to improve the signal processing speed of semiconductor chips and the like, a semiconductor substrate having a three-dimensional stacked structure has been put into practical use. The semiconductor substrate as described above is manufactured, for example, from a laminated wafer formed by bonding a first semiconductor wafer and a second semiconductor wafer with an adhesive or the like.

[0003] Specifically, after the back side of the first semiconductor wafer is ground and thinned, it is divided into individual device chips by a dicing device or the like.

[0004] However, since chamfering is performed on the outer peripheral portion of the semiconductor wafer, when the back side of the first semiconductor wafer is ground and thinned, the outer periphery of the wafer becomes a so-called knife edge, and chipping of the edge occurs during grinding.

[0005] As a countermeasure against such chipping, a method has been proposed in which edge trimming is performed on the chamfered portion of the first semiconductor wafer before grinding to remove the chamfered portion (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the method described in Patent Document 1, there is a risk that the cutting blade cuts into the surface side of the second wafer in the edge trimming step of removing the chamfered portion of the first wafer, leading to a deterioration in quality.

[0008] The present invention has been made in view of such a fact, and an object thereof is to provide a method for processing a laminated wafer that grinds and thins the laminated wafer without degrading the quality.

Means for Solving the Problems

[0009] In order to solve the above-described problems and achieve the object, a method for processing a laminated wafer according to the present invention is a method for processing a laminated wafer in which one surface side of a first wafer having an outer peripheral edge chamfered in an arc shape is joined to one surface side of a second wafer, and an external force is applied to the chamfered portion of the first wafer to separate the chamfered portion from the first wafer, thereby removing the chamfered portion. After the chamfered portion removing step, a grinding step of grinding the other surface side opposite to the one surface side of the first wafer is provided.

[0010] In the method for processing a laminated wafer, before the chamfered portion removing step, a chamfered portion weakening step of grinding the chamfered portion with a grindstone to remove a part of the chamfered portion may be further provided.

[0011] In the method for processing a laminated wafer, in the chamfered portion removing step, the chamfered portion may be ground from the other surface side of the first wafer with a grindstone, and the chamfered portion may be separated from the first wafer by the load during grinding.

[0012] In the method for processing a laminated wafer, in the chamfered portion removing step, the chamfered portion may be ground from the outer side in the radial direction of the first wafer with a grindstone, and the chamfered portion may be separated from the first wafer by the load during grinding.

[0013] In the method for processing a laminated wafer, in the chamfered portion removing step, the chamfered portion may be polished from the other surface side of the first wafer with a polishing pad, and the chamfered portion may be separated from the first wafer by the load during polishing.

[0014] In the method for processing the laminated wafer, in the chamfer removal step, the chamfer may be polished with a polishing pad from the outside in the radial direction of the first wafer, and the chamfer may be separated from the first wafer by the load during polishing.

[0015] In the method for processing the laminated wafer, in the chamfer removal step, the chamfer may be separated from the first wafer by applying ultrasonic waves to the chamfer.

Advantages of the Invention

[0016] The present invention has the effect that the laminated wafer can be ground and thinned without degrading the quality.

Brief Description of the Drawings

[0017]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0018] A mode (embodiment) 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 those that are substantially the same. 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.

[0019] 〔Embodiment 1〕 A method for processing a laminated wafer according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a configuration example of a laminated wafer to be processed in a method for processing a laminated wafer according to Embodiment 1. FIG. 2 is a flowchart showing the flow of a method for processing a laminated wafer according to Embodiment 1.

[0020] Workpiece The method for processing a stacked wafer according to Embodiment 1 is a method for processing the stacked wafer 1 shown in FIG. 1. In Embodiment 1, the stacked wafer 1 to be processed by the method for processing a stacked wafer includes a first wafer 10 and a second wafer 20. In Embodiment 1, the first wafer 10 and the second wafer 20 are wafers such as disk-shaped semiconductor wafers having a substrate such as silicon, gallium arsenide, or SiC (silicon carbide). Note that in Embodiment 1, the first wafer 10 and the second wafer 20 have the same configuration.

[0021] As shown in FIG. 1, a plurality of division planned lines intersecting (orthogonal in Embodiment 1) the surfaces 11 and 21 (corresponding to one surface) are set on the first wafer 10 and the second wafer 20, and devices are formed in a plurality of regions partitioned by the division planned lines, respectively. The devices are, for example, integrated circuits such as ICs (Integrated Circuits) or LSIs (Large Scale Integration), or various memories (semiconductor storage devices).

[0022] The stacked wafer 1 is configured by bonding the surface 11 side of the first wafer 10 and the surface 21 side of the second wafer 20. Also, in Embodiment 1, the surface 11 side of the first wafer 10 and the surface 21 side of the second wafer 20 are bonded by an adhesive layer 2 formed of an adhesive or the like. The stacked wafer 1 is divided into the first wafer 10 and the second wafer 20 along the division planned lines and is separated into individual device chips having a so-called three-dimensional stacked structure.

[0023] Also, in Embodiment 1, the first wafer 10 and the second wafer 20 each have a disk-shaped disk portion 13, 23 having flat surfaces 11, 21 parallel to each other and back surfaces 12, 22 (corresponding to the other surfaces) on the side opposite to the surfaces 11, 21, and chamfered portions 14, 24 integrally formed with the disk portions 13, 23 at the outer edges of the disk portions 13, 23. The chamfered portions 14, 24 are formed extending from the surfaces 11, 21 to the back surfaces 12, 22 and are formed in an arc-shaped cross section such that the center in the thickness direction is located on the outermost peripheral side.

[0024] Thus, in Embodiment 1, the first wafer 10 and the second wafer 20 each have a chamfered portion 14, 24, so that the outer peripheral edge is chamfered in an arc shape. In Embodiment 1, in the stacked wafer 1, the disk portion 13 of the first wafer 10 and the disk portion 23 of the second wafer 20 are joined to each other, and the chamfered portions 14, 24 are not joined to each other (i.e., are spaced apart without contacting each other).

[0025] Also, in Embodiment 1, functional layers 15, 25 are formed on at least the surfaces 11, 21 of the disk portions 13, 23 of the first wafer 10 and the second wafer 20. The functional layers 15, 25 include an inorganic film such as SiOF or BSG (SiOB), an organic film such as a polymer film of polyimide or parylene, or a low dielectric constant insulator film (hereinafter referred to as a Low-k film) made of carbon-containing silicon oxide (SiOCH), and a circuit layer including a conductive metal pattern or a metal film.

[0026] The Low-k film is stacked with the circuit layer to form a device. The circuit layer constitutes the circuit of the device. For this reason, the device is constituted by the Low-k films stacked on each other in the functional layer 15, 25 and the circuit layer stacked between the Low-k films. In the planned division line, the functional layer 15, 25 is constituted by the Low-k film.

[0027] (Method for processing a stacked wafer) The processing method of the laminated wafer according to Embodiment 1 is the processing method of the laminated wafer 1 shown in FIG. 1. As shown in FIG. 2, the processing method of the laminated wafer according to Embodiment 1 includes a holding step 101, a chamfer weakening step 102, a chamfer removing step 103, and a grinding step 104.

[0028] (Cutting device) Next, the holding step 101, the chamfer removing step 103, and the cutting device 30 for performing the chamfer removing step 103 will be described. FIG. 3 is a perspective view showing a configuration example of a cutting device that performs the holding step, the chamfer weakening step, and the chamfer removing step of the processing method of the laminated wafer shown in FIG. 2.

[0029] The cutting device 30 is a processing device that holds the laminated wafer 1 by a holding table 40 and performs cutting (equivalent to processing) with a cutting blade 51. As shown in FIG. 3, the cutting device 30 includes a holding table 40 that sucks and holds the laminated wafer 1 on a holding surface 41, a cutting unit 50 that cuts the laminated wafer 1 held by the holding table 40 with a cutting blade 51, an imaging unit 60 that images the laminated wafer 1 held on the holding table 40, and a control unit 90.

[0030] Further, as shown in FIG. 3, the cutting device 30 includes a moving unit 70 that relatively moves the holding table 40 and the cutting unit 50. The moving unit 70 includes an X-axis moving unit 71 that is a machining feed unit that feeds the holding table 40 in the X-axis direction parallel to the horizontal direction, a Y-axis moving unit 72 that is an indexing feed unit that indexes and feeds the cutting unit 50 in the Y-axis direction parallel to the horizontal direction and orthogonal to the X-axis direction, a Z-axis moving unit 73 that is a cutting feed unit that feeds the cutting unit 50 in the Z-axis direction parallel to the vertical direction orthogonal to both the X-axis direction and the Y-axis direction, and at least a rotational moving unit 74 that rotates the holding table 40 around an axis parallel to the Z-axis direction.

[0031] As shown in Fig. 3, the cutting device 30 is a so-called facing dual-type cutting device equipped with two cutting units 50, that is, a two-spindle dicing saw. The moving unit 70 of the cutting device 30 includes two Y-axis moving units 72 and two Z-axis moving units 73 respectively, and the two Y-axis moving units 72 and Z-axis moving units 73 correspond to the cutting units 50 respectively.

[0032] The X-axis moving unit 71 is installed on the device main body 31 and moves the holding table 40 together with the rotary moving unit 74 in the X-axis direction, which is the machining feed direction, so as to relatively machine-feed the holding table 40 and the cutting unit 50 along the X-axis direction. The Y-axis moving unit 72 is installed on the gantry support frame 32 erected from the device main body 31 and moves the corresponding cutting unit 50 in the Y-axis direction, which is the indexing feed direction, so as to relatively index-feed the holding table 40 and the cutting unit 50 along the Y-axis direction.

[0033] The Z-axis moving unit 73 is installed on the moving frame 33 moved in the Y-axis direction by the Y-axis moving unit 72 and moves the corresponding cutting unit 50 in the Z-axis direction, which is the plunge feed direction, so as to relatively plunge-feed the holding table 40 and the cutting unit 50 along the Z-axis direction.

[0034] The X-axis moving unit 71, the Y-axis moving unit 72 and the Z-axis moving unit 73 are provided with a well-known ball screw rotatably provided around the axis, a well-known motor for rotating the ball screw around the axis, and a well-known guide rail for movably supporting the holding table 40 or the cutting unit 50 in the X-axis direction, Y-axis direction or Z-axis direction. The rotary moving unit 74 includes a well-known motor or the like for rotating the holding table 40 around the axis.

[0035] The holding table 40 is disk-shaped, and the holding surface 41 for holding the stacked wafer 1 is formed of porous ceramic or the like. Further, the holding table 40 is movably provided in the X-axis direction across the processing area below the cutting unit 50 by the X-axis moving unit 71 and the loading / unloading area where the stacked wafer 1 is loaded and unloaded while being separated from below the cutting unit 50, and is rotatably provided around an axis parallel to the Z-axis direction by the rotational moving unit 74. The holding table 40 has the holding surface 41 connected to a vacuum suction source (not shown), and sucks and holds the stacked wafer 1 placed on the holding surface 41 by being sucked by the vacuum suction source.

[0036] The cutting unit 50 is a processing unit to which a cutting blade 51 for cutting the stacked wafer 1 held by the holding table 40 is detachably attached. The cutting unit 50 is attached to a second moving frame 34 that is movable in the Z-axis direction by the corresponding Z-axis moving unit 73, and is provided so as to be movable in the Y-axis direction by the Y-axis moving unit 72 and movable in the Z-axis direction by the Z-axis moving unit 73 with respect to the stacked wafer 1 held by the holding table 40. The cutting unit 50 can position the cutting blade 51 at an arbitrary position on the holding surface 41 of the holding table 40 by the Y-axis moving unit 72 and the Z-axis moving unit 73.

[0037] The cutting unit 50 includes a cutting blade 51, a spindle housing 52 attached to the lower end of the second moving frame 34 and provided so as to be movable in the Y-axis direction and the Z-axis direction by the Y-axis moving unit 72 and the Z-axis moving unit 73, a spindle 53 that serves as a rotating shaft rotatably provided around the axis of the spindle housing 52, a spindle motor (not shown) that rotates the spindle 53 around the axis, and a cutting water supply nozzle that supplies cutting water to the cutting blade.

[0038] The cutting blade 51 is an extremely thin grinding wheel having a substantially ring shape for cutting the laminated wafer 1. In Embodiment 1, the cutting blade 51 has at least an annular cutting edge 54 for cutting the laminated wafer 1. The cutting edge 54 is formed of abrasive grains such as diamond or CBN (Cubic Boron Nitride) and a bonding material (binder) such as metal or resin to have a predetermined thickness. In Embodiment 1, the cutting blade 51 is a so-called washer blade composed only of the cutting edge 211. However, in the present invention, a so-called hub blade having an annular base and a cutting edge 54 provided at the outer edge of the annular base may also be used.

[0039] The spindle housing 52 is attached to the lower end of the second moving frame 34 and is supported so as to be movable in the Z-axis direction by the Z-axis moving unit 73 and is supported so as to be movable in the Y-axis direction by the Y-axis moving unit 72 via the Z-axis moving unit 73 and the moving frame 3. The spindle housing 52 houses a portion excluding the tip of the spindle 53 and a spindle motor (not shown) and supports the spindle 53 so as to be rotatable about its axis.

[0040] The spindle 53 is one to which the cutting blade 51 is detachably fixed at its tip. The spindle 53 is rotated by a spindle motor (not shown) and the cutting blade 51 is attached to the tip portion. The axes of the spindle 53 and the cutting blade 51 of the cutting unit 50 are parallel to the Y-axis direction.

[0041] The imaging unit 60 images the stacked wafer 1 held by the holding table 40 and acquires an imaging image. The imaging unit 60 is fixed to the cutting unit 50 so as to move integrally with the cutting unit 50. The imaging unit 60 includes an imaging element that images the area to be cut of the stacked wafer 1 before cutting held by the holding table 40. The imaging element is, for example, a CCD (Charge-Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element. The imaging unit images the stacked wafer 1 held by the holding table 40, acquires an image for performing alignment such as aligning the stacked wafer 1 and the cutting blade 51, and outputs the acquired image to the control unit 90.

[0042] Further, the cutting device 30 includes an X-axis direction position detection unit (not shown) for detecting the position of the holding table 40 in the X-axis direction, a Y-axis direction position detection unit (not shown) for detecting the position of the cutting unit 50 in the Y-axis direction, and a Z-axis direction position detection unit for detecting the position of the cutting unit 50 in the Z-axis direction. The X-axis direction position detection unit and the Y-axis direction position detection unit can be composed of a linear scale parallel to the X-axis direction or the Y-axis direction and a reading head. The Z-axis direction position detection unit detects the position of the cutting unit 50 in the Z-axis direction by the pulses of the motor.

[0043] The X-axis direction position detection unit, the Y-axis direction position detection unit, and the Z-axis direction position detection unit output the positions of the holding table 40 in the X-axis direction, the cutting unit 50 in the Y-axis direction, or the Z-axis direction to the control unit 90. The angle detection unit outputs the angle from the reference position around the axis of the holding table 40 to the control unit 90. In the first embodiment, the positions of the components of the cutting device 30 in the X-axis direction, the Y-axis direction, and the Z-axis direction are determined based on a predetermined reference position (not shown).

[0044] Further, the cutting device 30 includes a cassette elevator 80 that places a cassette 35 containing the laminated wafer 1 before and after cutting and moves the cassette 35 in the Z-axis direction, a cleaning unit 81 that cleans the laminated wafer 1 after the cutting process, and a transfer unit (not shown) that transfers the laminated wafer 1 between the cassette 35, the holding table 40, and the cleaning unit 81.

[0045] The control unit 90 controls each component of the cutting device 30 to cause the cutting device 30 to perform a processing operation on the laminated wafer 1. The control unit 90 is a computer having 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 90 performs arithmetic processing according to a computer program stored in the storage device, and outputs a control signal for controlling the cutting device 30 to each component of the cutting device 30 via the input / output interface device.

[0046] The control unit 90 is connected to a display unit (not shown) constituted by a liquid crystal display device or the like that displays the state of the processing operation, the captured image, etc., an input unit (not shown) used when an operator registers processing conditions, etc., and a notification unit (not shown). The input unit is constituted by at least one of a touch panel provided on the display unit and an external input device such as a keyboard. The notification unit emits at least one of sound and light to notify the operator.

[0047] (Holding Step) Next, the holding step 101 will be described. FIG. 4 is a side view schematically showing a part of the holding step of the processing method of the laminated wafer shown in FIG. 2 in a cross section. The holding step 101 is a step of holding the laminated wafer 1 on the holding surface 41 of the holding table 40.

[0048] In Embodiment 1, a cassette 35 containing a plurality of stacked wafers 1 is placed on a cassette elevator 80, and a control unit 90 receives and registers processing conditions input by an operator from an input unit or the like. When the control unit 90 of the cutting device 30 receives a processing start instruction input by the operator from an input unit or the like, the cutting device 30 starts a processing operation, that is, a holding step 101.

[0049] In Embodiment 1, in the holding step 101, the cutting device 30 starts the rotation of a spindle 53 of a cutting unit 50, that is, a cutting blade 51, and starts the supply of cutting water to the cutting blade 51 under the control of the control unit 90. In Embodiment 1, in the holding step 101, the cutting device 30 controls the cassette elevator 80 and a transfer unit or the like under the control of the control unit 90 to take out one stacked wafer 1 before cutting from the cassette 35 and place the back surface 22 side of the second wafer 20 of the stacked wafer 1 on a holding surface 41 of a holding table 40 positioned in a loading / unloading area. In Embodiment 1, in the holding step 101, as shown in FIG. 4, the cutting device 30 sucks and holds the back surface 22 of the second wafer 20 of the stacked wafer 1 on the holding surface 41 of the holding table 40 positioned in the loading / unloading area under the control of the control unit 90.

[0050] (Chamfering part weakening step) FIG. 5 is a side view schematically showing, in partial cross section, a chamfering part weakening step of the processing method of the stacked wafer shown in FIG. 2. FIG. 6 is a cross-sectional view schematically showing a main part of the stacked wafer after the chamfering part weakening step of the processing method of the stacked wafer shown in FIG. 2. FIG. 7 is a cross-sectional view schematically showing a main part of a modified example of the stacked wafer shown in FIG. 6. The chamfering part weakening step 102 is a step of cutting (corresponding to grinding) the chamfering part 14 with a cutting edge 54 of a cutting blade 51 which is a grinding stone and removing a part of the chamfering part 14 before the chamfering part removing step 103.

[0051] In Embodiment 1, in chamfer portion weakening step 102, the cutting device 30 positions the holding table 40 holding the stacked wafer 1 in the processing area by the control unit 90 controlling the moving unit 70, and causes the imaging unit 60 to image the stacked wafer 1 to perform alignment. In Embodiment 1, in chamfer portion weakening step 102, as shown in FIG. 5, the cutting device 30 rotates the holding table 40 around the axis by the rotational movement unit 74 while cutting the outer peripheral surface 55 of the cutting edge 54 of the cutting blade 51 rotated around the axis into the chamfer portion 14 of the first wafer 10 from the back surface 12 side, and removes the back surface 12 side of the chamfer portion 14 of the first wafer 10 of the stacked wafer 1 over the entire circumference to form a stepped portion 16 on the outer peripheral edge of the first wafer 10.

[0052] In Embodiment 1, in chamfer portion weakening step 102, the outer peripheral surface 55 of the cutting edge 54 of the cutting blade 51 thicker than the width of the chamfer portion 14 is cut into the chamfer portion 14 and the outer edge portion of the disc portion 13 of the first wafer 10 from the back surface 12 side, and as shown in FIG. 6, the chamfer portion 14 and the outer edge portion of the disc portion 13 (region where no device is formed) are removed from the back surface 12 side of the first wafer 10 of the stacked wafer 1 to form a stepped portion 16 on the back surface 12 side of the first wafer 10 where the bottom 17 is closer to the back surface 12 than the functional layer 15, thereby weakening the chamfer portion 14. Further, in Embodiment 1, in chamfer portion weakening step 102, the stepped portion 16 is formed from the outer edge of the first wafer 10 to the outer edge portion of the disc portion 13, and the bottom 17 is formed flat and parallel to the front surface 11 and the back surface 12.

[0053] In the present invention, in chamfer portion weakening step 102, as shown in FIG. 7, the outer peripheral surface 55 of the cutting edge 54 of the cutting blade 51 thinner than the width of the chamfer portion 14 is cut into the boundary between the chamfer portion 14 and the disc portion 13 of the first wafer 10 from the back surface 12 side to form a groove 18 on the back surface 12 side of the first wafer 10 where the bottom is closer to the back surface 12 than the functional layer 15, and the chamfer portion 14 may be weakened.

[0054] (Chamfer portion removal step) FIG. 8 is a side view schematically showing in partial cross section a chamfer removal step of the method for processing a laminated wafer shown in FIG. 2. FIG. 9 is a cross-sectional view schematically showing in partial cross section a state in which the chamfer is removed in the chamfer removal step of the method for processing a laminated wafer shown in FIG. 2. FIG. 10 is a side view schematically showing in partial cross section a modified example of the chamfer removal step of the method for processing a laminated wafer shown in FIG. 2. FIG. 11 is a cross-sectional view schematically showing in partial cross section a state in which the thickness between the bottom of the step portion and the functional layer is measured in the chamfer removal step of the method for processing a laminated wafer shown in FIG. 2. FIG. 12 is a cross-sectional view schematically showing in partial cross section a state in which the step portion reaches the functional layer in the chamfer removal step of the method for processing a laminated wafer shown in FIG. 2.

[0055] The chamfer removal step 103 is a step of removing the chamfer 14 by applying an external force to the chamfer 14 of the first wafer 10 to separate the chamfer 14 from the first wafer 10. The chamfer removal step 103 is also a step of separating the chamfer 14, which is an unbonded region formed in an arc shape of the chamfer 14, from the disk portion 13, which is a bonded region, starting from the boundary between the chamfer 14 and the disk portion 13. The chamfer removal step 103 is also a step of applying an external force to the chamfer 14, which is an unbonded region, and dividing the first wafer 10 starting from the boundary between the disk portion 13 and the chamfer 14.

[0056] In Embodiment 1, in the chamfer removal step 103, the cutting device 30 positions the outer peripheral surface 55 of the cutting edge 54 of the cutting blade 51 that rotates around the axis above the bottom 17 of the stepped portion 16, lowers the cutting blade 51, and as shown in FIG. 8, while cutting the bottom 17 of the stepped portion 16 with the outer peripheral surface 55 of the cutting edge 54 of the cutting blade 51, rotates the holding table 40 around the axis. Then, since the disk portions 13 and 23 are joined to each other and the chamfer portions 14 and 24 are spaced apart from each other, an external force from the cutting edge 54 of the cutting blade 51 concentrates at the boundary between the disk portion 13 and the chamfer portion 14 of the first wafer 10, and as shown in FIG. 9, the chamfer portion 14 of the first wafer 10 is separated from the disk portion 13 starting from the boundary. Thus, in Embodiment 1, in the chamfer removal step 103, since the chamfer portion 14 of the first wafer 10 is separated from the disk portion 13 starting from the boundary between the disk portion 13 and the chamfer portion 14 of the first wafer 10, it is not necessary to lower the cutting blade 51 until the chamfer portion 14 of the first wafer 10 is removed.

[0057] Note that in the chamfer removal step 103, the grinding load may be increased by using the cutting edge 54 of the cutting blade 51 having larger abrasive grains than in the chamfer weakening step 102, or by gradually increasing the machining feed rate at which the cutting blade 51 is lowered. That is, in the chamfer removal step 103, a cutting blade 51 different from that in the chamfer weakening step 102 may be used.

[0058] Also, the same processing conditions as in the chamfer weakening step 102 may be used, or steps substantially the same as the chamfer removal step 103 may be used. Further, in the chamfer removal step 103, when lowering the cutting blade 51, for example, a plurality of repetitions of a 100 μm descent and a 10 μm ascent may be performed to apply an external force to the boundary of the first wafer 10.

[0059] Thus, in Embodiment 1, in the chamfer removal step 103, the chamfer portion 14 is cut with the cutting blade 51 from the back surface 12 side of the first wafer 10, and the chamfer portion 14 is separated from the disk portion 13 of the first wafer 10 by the load during cutting.

[0060] In Embodiment 1, in chamfer removal step 103, instead of the cutting blade 51, the outer peripheral surface 92 of a disk-shaped polishing pad 91 that rotates around an axis parallel to the Y-axis direction is positioned above the bottom 17 of the step portion 16 of the first wafer 10, and the polishing pad 91 is lowered. As shown in FIG. 10, while polishing the bottom 17 of the step portion 16 with the outer peripheral surface 92 of the polishing pad 91, the holding table 40 is rotated around the axis, so that the external force from the cutting edge 54 of the cutting blade 51 is concentrated at the boundary between the disk portion 13 and the chamfer portion 14 of the first wafer 10. Thus, in Embodiment 1, in chamfer removal step 103, the chamfer portion 14 may be polished with the outer peripheral surface 92 of the polishing pad 91 from the back surface 12 side of the first wafer 10, and the chamfer portion 14 may be separated from the disk portion 13 of the first wafer 10 due to the load during polishing.

[0061] In Embodiment 1, in chamfer removal step 103, as shown in FIG. 11, the cutting device 30 measures the thickness 19 of the substrate at the bottom 17 of the step portion 16, that is, the thickness 19 between the bottom 17 and the functional layer, with an optical interference type film thickness measuring instrument 99. In Embodiment 1, in chamfer removal step 103, based on the thickness 19 measured by the optical interference type film thickness measuring instrument 99, as shown in FIG. 12, the outer peripheral surface 55 of the cutting edge 54 of the cutting blade 51 is cut into the bottom 17 of the step portion 16 to reach the functional layer 15, that is, to remove the substrate at the bottom 17 of the step portion 16. In the present invention, in chamfer removal step 103, the step portion 16 may be made to reach the functional layer 15, that is, the substrate at the bottom 17 of the step portion 16 may be removed by etching such as wet etching or dry etching.

[0062] (Grinding step) FIG. 13 is a side view schematically showing in partial cross section the grinding step of the processing method of the laminated wafer shown in FIG. 2. Grinding step 104 is a step of grinding the back surface 12 side of the first wafer 10, which is opposite to the front surface 11 side, after chamfer removal step 103.

[0063] In Embodiment 1, in the grinding step 104, as shown in FIG. 13, the grinding device 110 sucks and holds the back surface 22 side of the second wafer 20 of the stacked wafer 1 on the holding surface 112 of the chuck table 111, rotates the grinding wheel 114 by the spindle 113, and rotates the chuck table 111 around the axis, and abuts the grinding stone 115 against the back surface 12 of the first wafer 10 of the stacked wafer 1 and approaches the chuck table 111 at a predetermined feed rate, thereby grinding the back surface 12 of the first wafer 10 of the stacked wafer 1 with the grinding stone 115. In Embodiment 1, in the grinding step 104, the grinding device 110 grinds the first wafer 10 until it reaches a predetermined thickness.

[0064] As described above, in the chamfer removal step 103 of the processing method of the stacked wafer according to Embodiment 1, after applying an external force to the chamfer 14 of the first wafer 10 to separate the chamfer 14 from the disc portion 13 of the first wafer 10, in the grinding step 104, the first wafer 10 is ground. For this reason, in the processing method of the stacked wafer according to Embodiment 1, when removing the chamfer 14 of the first wafer 10, the cutting blade 51 does not cut into the surface 21 of the second wafer 20.

[0065] As a result, the processing method of the stacked wafer according to Embodiment 1 has the effect that the stacked wafer 1 can be ground and thinned without degrading the quality.

[0066] In addition, in the chamfer removal step 103 of the processing method of the stacked wafer according to Embodiment 1, as shown in FIG. 10, when separating the chamfer 14 using the polishing pad 91, after separating the chamfer 14, the outer peripheral surface of the first wafer 10 is polished with the polishing pad 91, so that damage such as cutting strain generated in the chamfer weakening step 102 can be removed.

[0067] 〔Embodiment 2〕 The processing method of the laminated wafer according to Embodiment 2 will be described with reference to the drawings. FIG. 14 is a side view schematically showing in partial cross section the chamfered portion removal step of the processing method of the laminated wafer according to Embodiment 2. FIG. 15 is a cross-sectional view schematically showing in partial cross section the state in which the chamfered portion is removed in the chamfered portion removal step of the processing method of the laminated wafer according to Embodiment 2. FIG. 16 is a side view schematically showing in partial cross section the chamfered portion removal step of the processing method of the laminated wafer according to a modification of Embodiment 2. In FIGS. 14, 15, and 16, the same reference numerals are given to the same parts as in Embodiment 1, and the description thereof is omitted.

[0068] The processing method of the laminated wafer according to Embodiment 2 is the same as that of Embodiment 1, except that in the chamfered portion weakening step 102, a stepped portion 16 is formed only on the chamfered portion 14 of the first wafer 10, and the chamfered portion removal step 103 is different. In Embodiment 2, in the chamfered portion weakening step 102, the stepped portion 16 is formed from the back surface 12 side of the first wafer 10 across the outer edge of the first wafer 10, the boundary between the disk portion 13 of the first wafer 10, and the chamfered portion 14.

[0069] In Embodiment 2, in the chamfer removal step 103, the cutting device 30 positions the ring-shaped side surface 56 of the cutting edge 54 of the cutting blade 51 that rotates around the axis outside the chamfer 14 of the first wafer 10, moves the cutting blade 51 in the Y-axis direction, and as shown in FIG. 14, while bringing the side surface 56 of the cutting edge 54 of the cutting blade 51 into contact with the outer edge of the chamfer 14 of the first wafer 10, the holding table 40 is rotated around the axis while moving the cutting blade 51 to the inner peripheral side of the first wafer 10. In Embodiment 2, in the chamfer removal step 103, an external force from the cutting edge 54 of the cutting blade 51 is concentrated at the boundary between the disc portion 13 and the chamfer 14 of the first wafer 10, and as shown in FIG. 15, the chamfer 14 of the first wafer 10 is separated from the disc portion 13 starting from the boundary. Thus, in Embodiment 2, in the chamfer removal step 103, the chamfer 14 is cut with the cutting edge 54 of the cutting blade 51 from the outer side in the radial direction of the first wafer 10, and the chamfer 14 is separated from the disc portion 13 of the first wafer 10 by the load during cutting.

[0070] Note that in Embodiment 2, in the chamfer removal step 103, it is desirable to increase the grinding load by using the cutting edge 54 of the cutting blade 51 having larger abrasive grains than in the chamfer weakening step 102, or by gradually increasing the machining feed rate at which the cutting blade 51 is moved in the Y-axis direction.

[0071] The processing method of the stacked wafer according to Embodiment 2 applies an external force to the chamfer 14 of the first wafer 10 in the chamfer removal step 103 to separate the chamfer 14 from the disc portion 13 of the first wafer 10. Thus, similar to Embodiment 1, there is an effect that the stacked wafer 1 can be ground and thinned without degrading the quality.

[0072] Also, in order to prevent becoming a knife edge, conventional edge trimming is performed, and then etching to remove the substrate at the bottom 17 of the step portion 16 may be considered. In this case, however, there is a risk that the disc portion 13 of the first wafer 10, that is, the region where the device is formed, may also be etched during etching.

[0073] For such conventional edge trimming, in the chamfer removal step 103 of the processing method of the laminated wafer according to Embodiment 2, since an external force is applied to remove the chamfer 14, there is no possibility that the disk portion 13 of the first wafer 10, that is, the region where the device is formed, will be etched.

[0074] In Embodiment 2, instead of the cutting blade 51, the ring-shaped polishing surface 93 of the disk-shaped polishing pad 91 that rotates around the axis is positioned outside the outer circumference of the chamfer 14 of the first wafer 10, and the polishing pad 91 is moved in the Y-axis direction. As shown in FIG. 16, while the polishing surface 93 of the polishing pad 91 is brought into contact with the outer edge of the chamfer 14 of the first wafer 10, the holding table 40 is rotated around the axis while the polishing pad 91 is moved to the inner circumference side of the first wafer 10, so that the external force from the cutting edge 54 of the cutting blade 51 is concentrated at the boundary between the disk portion 13 and the chamfer 14 of the first wafer 10. Thus, in Embodiment 2, in the chamfer removal step 103, the chamfer 14 may be polished with the polishing pad 91 from the outer side in the radial direction of the first wafer 10, and the chamfer 14 may be separated from the disk portion 13 of the first wafer 10 by the load during polishing.

[0075] In this case, in addition to the effects of Embodiment 2 described above, after the separation of the chamfer 14, since the outer peripheral surface of the first wafer 10 is polished with the polishing pad 91, damage such as cutting distortion generated in the chamfer weakening step 102 can be removed.

[0076] 〔Embodiment 3〕 The processing method of the laminated wafer according to Embodiment 3 will be described with reference to the drawings. FIG. 17 is a side view schematically showing in partial cross section the chamfer removal step of the processing method of the laminated wafer according to Embodiment 3. FIG. 18 is a cross-sectional view schematically showing in partial cross section the state in which the chamfer is removed in the chamfer removal step of the processing method of the laminated wafer according to Embodiment 3. FIG. 19 is a side view schematically showing in partial cross section the chamfer removal step of the processing method of the laminated wafer according to a modification of Embodiment 3. FIG. 20 is a cross-sectional view schematically showing in partial cross section the state in which the chamfer is removed in the chamfer removal step of the processing method of the laminated wafer according to a modification of Embodiment 3. In FIGS. 17, 18, 19, and 20, the same reference numerals are given to the same parts as in Embodiment 1, and the description thereof is omitted.

[0077] The processing method of the laminated wafer according to Embodiment 3 is the same as that of Embodiment 1, except that in the chamfer weakening step 102, a stepped portion 16 is formed only on the chamfer portion 14 of the first wafer 10, and the chamfer removal step 103 is different. In Embodiment 3, similar to Embodiment 2, in the chamfer weakening step 102, the stepped portion 16 is formed from the back surface 12 side of the first wafer 10 across the outer edge of the first wafer 10, the disk portion 13 of the first wafer 10, and the boundary between the chamfer portion 14.

[0078] In Embodiment 3, in the chamfer removal step 103, as shown in FIG. 17, an ultrasonic vibrator 120 that generates ultrasonic vibration 121 by a piezoelectric element or the like is brought into contact with the bottom 17 of the stepped portion 16 formed from the back surface 12 side on the chamfer portion 14 of the first wafer 10 of the laminated wafer 1. In Embodiment 3, in the chamfer removal step 103, an external force from the ultrasonic vibration 121 of the ultrasonic vibrator 120 is concentrated at the boundary between the disk portion 13 and the chamfer portion 14 of the first wafer 10, and as shown in FIG. 18, the chamfer portion 14 of the first wafer 10 is separated from the disk portion 13 starting from the boundary.

[0079] Also, in Embodiment 3, in the chamfer removal step 103, as shown in FIG. 19, an ultrasonic vibrator 120 that generates ultrasonic vibration 121 by a piezoelectric element or the like is disposed opposite to the bottom 17 of a stepped portion 16 formed on the back surface 12 side of the chamfer portion 14 of the first wafer 10 of the laminated wafer 1, and liquid 123 may be supplied from a liquid supply nozzle 122 between the ultrasonic vibrator 120 and the bottom 17 of the stepped portion 16. Also in this case, in the chamfer removal step 103, an external force from the ultrasonic vibration 121 of the ultrasonic vibrator 120 is concentrated at the boundary between the disc portion 13 and the chamfer portion 14 of the first wafer 10, and as shown in FIG. 20, the chamfer portion 14 of the first wafer 10 is separated from the disc portion 13 starting from the boundary. In the cases shown in FIGS. 19 and 20, it is desirable that the temperature and type of the liquid 123 be set as appropriate.

[0080] Thus, in Embodiment 3, in the chamfer removal step 103, by applying ultrasonic vibration 121 to the chamfer portion 14, the chamfer portion 14 is separated from the disc portion 13 of the first wafer 10.

[0081] In the method for processing a laminated wafer according to Embodiment 3, in the chamfer removal step 103, an external force is applied to the chamfer portion 14 of the first wafer 10 to separate the chamfer portion 14 from the disc portion 13 of the first wafer 10. Thus, similar to Embodiment 1, the laminated wafer 1 can be ground and thinned without degrading the quality.

[0082] Also, in the method for processing a laminated wafer according to Embodiment 3, similar to Embodiment 2, in the chamfer removal step 103, an external force is applied to remove the chamfer portion 14, so there is no risk that the disc portion 13 of the first wafer 10, i.e., the region where the device is formed, will be etched.

[0083] 〔Embodiment 4〕 The processing method of the stacked wafer according to Embodiment 4 will be described with reference to the drawings. FIG. 21 is a side view schematically showing in partial cross-section the chamfer removal step of the processing method of the stacked wafer according to Embodiment 4. FIG. 22 is a cross-sectional view schematically showing in partial cross-section the state in which the chamfer is removed in the chamfer removal step of the processing method of the stacked wafer according to Embodiment 4. In FIGS. 21 and 22, the same parts as those in Embodiment 1 are denoted by the same reference numerals and the description thereof is omitted.

[0084] The processing method of the stacked wafer according to Embodiment 4 is the same as that of Embodiment 1, except that in the chamfer weakening step 102, a stepped portion 16 is formed only on the chamfer portion 14 of the first wafer 10, and the chamfer removal step 103 is different. In Embodiment 4, similar to Embodiment 2, in the chamfer weakening step 102, the stepped portion 16 is formed from the back surface 12 side of the first wafer 10 across the outer edge of the first wafer 10, the disc portion 13 of the first wafer 10, and the boundary between the chamfer portion 14.

[0085] In Embodiment 4, in the chamfer removal step 103, as shown in FIG. 21, the fluid injection nozzle 130 is opposed to the bottom 17 of the stepped portion 16 formed on the chamfer portion 14 of the first wafer 10 of the stacked wafer 1 from the back surface 12 side, and the fluid 131 is injected from the fluid injection nozzle 130 to the bottom 17 of the stepped portion 16. In Embodiment 4, in the chamfer removal step 103, an external force from the fluid 131 is concentrated at the boundary between the disc portion 13 and the chamfer portion 14 of the first wafer 10, and as shown in FIG. 22, the chamfer portion 14 of the first wafer 10 is separated from the disc portion 13 starting from the boundary. The fluid 131 may be a liquid (water), a gas (air), or a two-fluid mixture of water and air. Also, in Embodiment 4, the fluid 131 may be injected from the outer peripheral side, the lower surface side, or obliquely.

[0086] In the chamfer removal step 103 of the processing method of the laminated wafer according to Embodiment 4, an external force is applied to the chamfer portion 14 of the first wafer 10 to separate the chamfer portion 14 from the disc portion 13 of the first wafer 10. Therefore, similar to Embodiment 1, the laminated wafer 1 can be ground and thinned without degrading the quality.

[0087] In addition, in the processing method of the laminated wafer according to Embodiment 4, similar to Embodiment 2, in the chamfer removal step 103, an external force is applied to remove the chamfer portion 14. Therefore, there is no risk that the disc portion 13 of the first wafer 10, that is, the region where the device is formed, will be etched.

[0088] In addition, in the processing method of the laminated wafer according to Embodiment 4, in the chamfer removal step 103, the fluid 131 is injected to separate the chamfer portion 14, so that it is possible to remove the grinding debris generated in the chamfer weakening step 102.

[0089] [Embodiment 5] The processing method of the laminated wafer according to Embodiment 5 will be described with reference to the drawings. FIG. 23 is a side view schematically showing a chamfer removal step of the processing method of the laminated wafer according to Embodiment 5 in a partial cross section. FIG. 24 is a cross-sectional view schematically showing a state in which the chamfer portion is removed in the chamfer removal step of the processing method of the laminated wafer according to Embodiment 5 in a partial cross section. In FIGS. 23 and 24, the same parts as those in Embodiment 1 are denoted by the same reference numerals and the description thereof is omitted.

[0090] The processing method of the laminated wafer according to Embodiment 5 is the same as that of Embodiment 1 except that in the chamfer weakening step 102, a step portion 16 is formed only on the chamfer portion 14 of the first wafer 10, and the chamfer removal step 103 is different. In Embodiment 5, similar to Embodiment 2, in the chamfer weakening step 102, the step portion 16 is formed from the back surface 12 side of the first wafer 10 across the outer edge of the first wafer 10, the boundary between the disc portion 13 of the first wafer 10, and the chamfer portion 14.

[0091] In Embodiment 5, in the chamfered portion removal step 103, as shown in FIG. 23, the tip 141 of the pin 140 is brought into contact with the bottom 17 of the step portion 16 formed from the back surface 12 side of the chamfered portion 14 of the first wafer 10 of the laminated wafer 1 on the fluid injection nozzle 130, and the pin 140 is lowered. In Embodiment 5, in the chamfered portion removal step 103, the external force from the pin 140 of the ultrasonic vibrator 120 is concentrated at the boundary between the disc portion 13 and the chamfered portion 14 of the first wafer 10, and as shown in FIG. 24, the chamfered portion 14 of the first wafer 10 is separated from the disc portion 13 starting from the boundary. In Embodiment 5, the pin 140 may be pressed from the outer peripheral side, the lower surface side, or obliquely.

[0092] In the processing method of the laminated wafer according to Embodiment 5, in the chamfered portion removal step 103, an external force is applied to the chamfered portion 14 of the first wafer 10 to separate the chamfered portion 14 from the disc portion 13 of the first wafer 10. Thus, similar to Embodiment 1, there is an effect that the laminated wafer 1 can be ground and thinned without degrading the quality.

[0093] Also, in the processing method of the laminated wafer according to Embodiment 5, similar to Embodiment 2, with respect to the conventional edge trimming, in the chamfered portion removal step 103, an external force is applied to remove the chamfered portion 14. Therefore, there is no risk that the disc portion 13 of the first wafer 10, that is, the region where the device is formed, will be etched.

[0094] Note that the present invention is not limited to the above-described embodiments. That is, various modifications can be made and implemented without departing from the gist of the present invention. In the present invention, it is preferable but not essential to perform the chamfered portion weakening step 102 before the chamfered portion removal step 103. Also, in the present invention, in the chamfered portion removal step 103, if there is a bonding defect radially inside the chamfered portions 14 and 24 due to reasons such as the surface 11 and 21 shapes of the wafers 10 and 20 between the disc portion 13 of the first wafer 10 and the disc portion 13 of the second wafer 20, the first wafer 10 may be divided at the interface between the bonding defect region and the bonding region.

Explanation of Reference Numerals

[0095] 1 Stacked wafer 10 First wafer 11 Front surface (one side) 12 Back surface (the other side) 14 Chamfered portion 20 Second wafer 21 Front surface (one side) 22 Back surface (the other side) 54 Cutting edge (grinding stone) 91 Polishing pad 102 Chamfered portion weakening step 103 Chamfered portion removal step 104 Grinding step 121 Ultrasonic vibration (ultrasound)

Claims

1. A processing method for laminated wafers in which one surface side of a first wafer, the outer circumferential edge of which is chamfered into an arc shape, and one surface side of a second wafer are bonded together, the method comprising the steps of: a chamfer removing step of applying an external force to the chamfer of the first wafer to separate the chamfer from the first wafer, thereby removing the chamfer; The method for processing stacked wafers includes, after the chamfered portion removing step, a grinding step of grinding the other surface side of the first wafer opposite to the one surface side.

2. Prior to the chamfer removing step, 2. The method for processing laminated wafers according to claim 1, further comprising a chamfer weakening step of grinding the chamfer with a grindstone to remove a portion of the chamfer.

3. In the chamfer removing step, 3. A method for processing stacked wafers according to claim 1 or claim 2, characterized in that the chamfered portion is ground from the other surface side of the first wafer with a grindstone, and the chamfered portion is separated from the first wafer by the load during grinding.

4. In the chamfer removing step, 3. A method for processing stacked wafers according to claim 1 or claim 2, characterized in that the chamfered portion is ground from the radially outer side of the first wafer with a grinding wheel, and the chamfered portion is separated from the first wafer by the load applied during grinding.

5. In the chamfer removing step, 3. A method for processing stacked wafers as claimed in claim 1 or claim 2, characterized in that the chamfered portion is polished from the other side of the first wafer with a polishing pad, and the chamfered portion is separated from the first wafer by the load during polishing.

6. In the chamfer removing step, 3. A method for processing stacked wafers as described in claim 1 or claim 2, characterized in that the chamfered portion is polished with a polishing pad from the radially outer side of the first wafer, and the chamfered portion is separated from the first wafer by the load during polishing.

7. In the chamfer removing step, 3. The method for processing laminated wafers according to claim 1, further comprising the step of applying ultrasonic waves to the chamfered portion to separate the chamfered portion from the first wafer.

Images