JP7650581B2 - Cutting device and cutting method - Google Patents

Description

The present invention relates to a cutting device that cuts the outer periphery of the front surface of a wafer whose front and back surfaces have been chamfered, forming an annular step on the front surface, and a cutting method that uses the cutting device to form an annular step on the front surface of a wafer.

In disk-shaped workpieces such as silicon semiconductor wafers, the outer periphery of each of the front and back sides is usually chamfered (i.e., a bevel portion is formed on each of the outer periphery of each of the front and back sides).

When such a workpiece is thinned to less than half its original thickness, a so-called sharp edge (also called a knife edge) is formed on the outer periphery, making the outer periphery more susceptible to damage. Therefore, in order to prevent damage to the outer periphery, a technique is known in which the outer periphery on the front side is cut to a predetermined depth with a cutting blade to form an annular step (i.e., after edge trimming is performed), and then the back side is ground to thin it (see, for example, Patent Document 1).

JP 2000-173961 A

However, the step portion formed by edge trimming may have a variation in thickness. For example, if the cutting depth of the cutting blade is less than the target cutting depth, a knife edge is formed even if the back side is ground. Also, for example, if the cutting depth of the cutting blade exceeds the target cutting depth, wear of the cutting edge of the cutting blade is accelerated.

The present invention was made in consideration of these problems, and aims to reduce the variation in thickness of the step portion during edge trimming.

According to one aspect of the present invention, there is provided a cutting device for cutting the outer periphery on the front side of a workpiece having a chamfered outer periphery on each of the front and back sides, and forming an annular step portion on the front side, the cutting device comprising: a chuck table having a holding surface for holding the back side of the workpiece and rotatable around a predetermined rotation axis while the workpiece is held on the holding surface; a cutting unit having a spindle to which a cutting blade is attached at one end, and cutting the outer periphery on the front side with the cutting blade attached to the spindle to form the step portion; a displacement meter ; and a processor, the thickness gauge measuring a first distance from the displacement meter to an upper surface of the outer periphery of the chuck table and a second distance from the displacement meter to an upper surface of the step portion of the workpiece with the displacement meter, and measuring a thickness of the step portion by calculating a difference between the first distance and the second distance ; and a control unit for controlling the chuck table, the cutting unit, and the thickness gauge, the control unit having a memory section for storing a rotation angle of the chuck table and a thickness of the step portion corresponding to the rotation angle, and a correction section for calculating a correction value for the infeed amount of the cutting unit during cutting based on the thickness of the step portion calculated by the thickness gauge, the data of the thickness of the step portion relative to a reference height position stored in the memory section, and a deviation from a predetermined target depth position relative to the reference height position, and the control unit adjusts the infeed amount of the cutting unit using the correction value, thereby reducing variation in the thickness of annular step portion in other workpieces different from the workpiece, or variation in the thickness of the step portion in the workpiece.

Preferably, the displacement meter is a laser displacement meter.

According to another aspect of the present invention, there is provided a cutting method for cutting a front surface side of a workpiece having outer peripheries on both the front surface side and the back surface side chamfered by using a cutting device including a chuck table and a cutting unit to which a cutting blade is attached, the cutting method including an upper surface measuring step of measuring a first distance from a displacement meter to an upper surface of the outer periphery of the chuck table by the displacement meter, a holding step of holding the back surface side of the workpiece with a holding surface of the chuck table, a cutting step of forming the step portion on the front surface side by positioning a lower end of the cutting blade at a predetermined target depth position in the outer periphery and rotating the chuck table at least 360 degrees around a predetermined rotation axis after the cutting step, and a cutting step of rotating the chuck table at least 360 degrees around the predetermined rotation axis to form the step portion on the front surface side. the thickness measuring step of measuring a thickness of the step portion along the circumferential direction of the workpiece using a thickness measuring device having a displacement meter arranged toward the upper surface of the step portion of the workpiece and a processor , the thickness measuring step calculating a difference between the first distance and a second distance measured using the displacement meter to an upper surface of the step portion of the workpiece; and a correction value calculating step of calculating a correction value for the infeed amount of the cutting unit based on a deviation between thickness data of the step portion corresponding to a rotation angle of the chuck table, the thickness data being relative to a reference height position and a predetermined target depth position relative to the reference height position, and adjusting the infeed amount of the cutting unit using the correction value to reduce a variation in thickness of the annular step portion in a workpiece different from the workpiece, or a variation in thickness of the step portion in the workpiece.

According to yet another aspect of the present invention, there is provided a cutting method for cutting a front surface side of a workpiece having outer peripheries chamfered on the front and back surfaces thereof by using a cutting device including a chuck table and a cutting unit to which a cutting blade is attached, the cutting method including an upper surface measuring step of measuring a first distance from a displacement meter to an upper surface of the outer periphery of the chuck table by the displacement meter; a holding step of holding the back surface side of the workpiece with a holding surface of the chuck table; a provisional cutting step of, after the holding step, positioning a lower end of the cutting blade at a provisional cutting target depth position shallower than a predetermined target depth position on the outer periphery and rotating the chuck table at least 360 degrees around a predetermined rotation axis to form a provisional cutting step on the front surface side; and , after the provisional cutting step, rotating the chuck table at least 360 degrees around the predetermined rotation axis to form a provisional cutting step on the front surface side. a thickness measuring step of measuring a thickness of the provisionally cut step portion along the circumferential direction of the workpiece using a thickness gauge that calculates the difference between the first distance and a second distance from the displacement meter to an upper surface of the step portion of the workpiece, the thickness measuring step being performed after the thickness measuring step, a correction value calculating step of calculating a correction value for a cutting feed amount of the cutting unit based on a deviation between thickness data of the provisionally cut step portion corresponding to a rotation angle of the chuck table, the thickness data being for a reference height position and a predetermined target depth position for the reference height position, and a main cutting step of positioning a lower end of the cutting blade at a position of the predetermined target depth on the outer periphery and rotating the chuck table at least 360 degrees around the predetermined rotation axis to form the step portion on the front surface side, and the cutting method reduces variation in thickness of the step portion in the workpiece by adjusting the cutting feed amount of the cutting unit using the correction value.

A cutting device according to one aspect of the present invention includes a chuck table, a cutting unit, a thickness gauge for measuring the thickness of the step portion, and a control unit for controlling the chuck table, the cutting unit, and the thickness gauge.

The control unit has a memory section that stores the rotation angle of the chuck table and the thickness of the step portion corresponding to the rotation angle, and a correction section that calculates a correction value for the infeed amount of the cutting unit during cutting based on the data on the thickness of the step portion stored in the memory section. The control unit corrects the infeed amount of the cutting unit according to the correction value, thereby reducing the variation in the thickness of the step portion.

FIG. FIG. FIG. 2 is a flow diagram of a cutting method according to the first embodiment. FIG. 4A is a diagram showing the upper surface measuring step, and FIG. 4B is a diagram showing the holding step. FIG. 5A is a partial cross-sectional side view showing the first cutting step, and FIG. 5B is a perspective view showing the first cutting step. FIG. 2 is a diagram showing a thickness measurement step. FIG. 7A is a graph showing the variation in thickness of the step portion, and FIG. 7B is a graph showing the correction values. FIG. 11 is a perspective view showing a second cutting step. FIG. 11 is a flowchart of a cutting method according to a second embodiment. FIG. 10A is a diagram showing a provisional cutting step, FIG. 10B is a diagram showing a thickness measurement step, and FIG. 10C is a diagram showing a main cutting step.

An embodiment of the present invention will be described with reference to the attached drawings. First, a cutting device 2 according to a first embodiment will be described with reference to Figs. 1 and 2. Fig. 1 is a perspective view of the cutting device 2, and Fig. 2 is a partial cross-sectional side view of the cutting device 2.

The X-axis direction (machining feed direction), Y-axis direction (indexing feed direction), and Z-axis direction (vertical direction, height direction) shown in Figures 1 and 2 are mutually perpendicular. The cutting device 2 has a base 4 that supports or houses each component.

A cover 6 is provided on the top of the base 4, forming a top surface and multiple side surfaces. A cutting unit 8 is housed inside the cover 6. The cutting unit 8 has a rectangular column-shaped spindle housing 10.

The spindle housing 10 is arranged so that its longitudinal direction is approximately parallel to the Y-axis direction. As shown in FIG. 2, the spindle housing 10 accommodates a portion of the cylindrical spindle 12 in a rotatable manner.

An annular cutting blade 16 is attached to one end of the spindle 12. The cutting blade 16 is, for example, a hub-type blade, and has an annular base made of a metal such as aluminum and a cutting edge 16a arranged in an annular shape on the outer periphery of the base.

The thickness of the cutting blade 16a is greater than the thickness of the cutting blade used to divide the workpiece 11 into multiple chips. The thickness of the cutting blade 16a is, for example, 1 mm or more and 3 mm or less. A rotation drive source 14 such as a servo motor is connected to the other end of the spindle 12.

The spindle housing 10 is connected to a Z-axis movement mechanism 20. The Z-axis movement mechanism 20 has a pair of guide rails 22. A Z-axis movement plate (not shown) is slidably attached to the pair of guide rails 22.

The spindle housing 10 is fixed to the front side of the Z-axis moving plate, and a nut portion (not shown) is provided on the back side of the Z-axis moving plate. A ball screw 24 is rotatably connected to the nut portion, which is disposed along the Z-axis direction between a pair of guide rails 22.

When the ball screw 24 is rotated by a rotary drive source 26 such as a pulse motor connected to the upper end of the ball screw 24, the cutting unit 8 moves along the Z-axis direction. The Z-axis movement mechanism 20 is disposed on the front side of the Y-axis movement plate 30.

The Y-axis moving plate 30 is slidably attached to a pair of guide rails 32 arranged along the Y-axis direction. Note that only one of the guide rails 32 is shown in FIG. 2. A ball screw 34 is arranged along the Y-axis direction between the pair of guide rails 32.

A nut portion (not shown) provided on the back side of the Y-axis moving plate 30 is rotatably connected to the ball screw 34. A rotary drive source 36 such as a pulse motor is connected to one end of the ball screw 34. When the ball screw 34 is rotated by the rotary drive source 36, the cutting unit 8 and the Z-axis moving mechanism 20 move along the Y-axis direction.

A chuck table 38 for suction-holding the workpiece 11 is provided below the cutting unit 8. A rotation mechanism 40 for rotating the chuck table 38 around a predetermined rotation axis 40a that is approximately parallel to the Z-axis direction is connected to the lower part of the chuck table 38.

An X-axis movement mechanism (not shown) that moves the chuck table 38 and the rotation mechanism 40 along the X-axis direction is provided below the rotation mechanism 40. The chuck table 38 has a disk-shaped frame 42 made of metal or the like.

A disk-shaped recess is formed in the upper part of the frame 42, and a disk-shaped porous plate 44 made of porous ceramics is fixed in this recess. A flow path (not shown) is formed in the frame 42, and one end of the flow path is connected to the lower surface of the porous plate 44.

The other end of the flow path is connected to a suction source (not shown) such as an ejector, and when the suction source is operated, negative pressure is generated on the upper surface 44a of the porous plate 44. The upper surface 44a of the porous plate 44 is flush with the upper surface 42a of the frame 42.

The upper surfaces 42a and 44a form a substantially flat holding surface 38a for suction-holding the workpiece 11. A thickness gauge 46 is disposed above the chuck table 38. In this embodiment, the thickness gauge 46 has a laser displacement meter 48.

The laser displacement meter 48 is disposed at a predetermined position above the upper surface 42a of the frame 42 (the outer periphery of the chuck table 38). The laser displacement meter 48 is also called a laser level sensor.

The laser displacement meter 48 is, for example, a spectroscopic interference type laser displacement meter having an SLD (Super Luminescent Diode) light source, and is used to measure the distance to an object in a non-contact manner using a laser beam.

By rotating the chuck table 38 once while irradiating a laser beam from the laser displacement meter 48 to a single point on the upper surface 42a, a first distance _A1 (see Figure 4 (A)) from the laser displacement meter 48 to the upper surface 42a can be measured along the circumferential direction of the upper surface 42a.

In addition, when the back surface 11b of the workpiece 11 (see FIG. 4B) is held by suction with the holding surface 38a and a laser beam is irradiated onto a point on the outer periphery of the front surface 11a of the workpiece 11, the chuck table 38 is rotated once, and the distance from the laser displacement meter 48 to the front surface 11a can be measured along the circumferential direction of the front surface 11a.

The thickness of the workpiece 11 at a point on the surface 11a is calculated by calculating the difference between the distance from the laser displacement meter 48 to the point on the surface _11a and a first distance A1 from the laser displacement meter 48 to the upper surface 42a of the frame 42 at the same XY coordinates as the point.

The workpiece 11 is, for example, a disk-shaped semiconductor wafer made of silicon. In this embodiment, two types of workpieces 11 are used. The first type of workpiece 11 is a so-called dummy wafer, such as an NP (Non Product) wafer or a QC (Quality Control) wafer.

The dummy wafer does not have any devices such as ICs (Integrated Circuits) or LSIs (Large Scale Integration) formed on it (see Figures 4(B), 5(A), and 5(B)). In the first embodiment, this dummy wafer is used to first obtain a correction value for the infeed amount of the cutting blade 16 during edge trimming.

Next, edge trimming is performed on a second type of workpiece 11 (device wafer) on which a device is formed, while adjusting the cutting feed amount with high precision using the acquired correction value.

A plurality of planned division lines (streets) 15 are set on the surface 11a of the second type of workpiece 11, and devices 17 such as ICs and LSIs are formed in each area defined by the plurality of planned division lines 15 (see Figure 8).

However, both the dummy wafer and the device wafer have approximately the same diameter and thickness, and the outer periphery on the front surface 11a side and the outer periphery on the back surface 11b side are chamfered. Now, returning to Figure 1, other configurations of the cutting device 2 will be described.

As shown in FIG. 1, a cassette table 50 is provided at a corner of the base 4. A cassette (not shown) containing multiple workpieces 11 is placed on the upper surface of the cassette table 50. A touch panel display device 52 that functions as a display unit and an input unit is provided on the front surface 6a of the cover 6.

The cutting device 2 is provided with a control unit 54 that controls the operation of the cutting unit 8, Z-axis movement mechanism 20, Y-axis movement mechanism 28, chuck table 38, suction source, rotation mechanism 40, X-axis movement mechanism, thickness gauge 46, cassette table 50, display device 52, etc.

The control unit 54 is composed of a computer including, for example, a processor (processing device) represented by a CPU (Central Processing Unit), a main memory device such as a DRAM (Dynamic Random Access Memory), an SRAM (Static Random Access Memory), or a ROM (Read Only Memory), and an auxiliary memory device such as a flash memory, a hard disk drive, or a solid state drive.

The auxiliary storage device stores software including a specific program. The functions of the control unit 54 are realized by operating the processing device and the like in accordance with this software.

A part of the resources of the auxiliary storage device functions as a memory unit 56 that stores the rotation angle θ of the rotation mechanism 40 and the thickness 11d of the step portion 11c at a position corresponding to the rotation angle (see FIG. 6). Furthermore, a program stored in another part of the resources of the auxiliary storage device functions as a correction unit 58.

The correction unit 58 calculates the thickness 11d of the step portion 11c based on the difference between the first distance _A1 (see Figure 4(A)) from the laser displacement meter 48 to the upper surface 11e of the step portion 11c and the second distance _A2 (see Figure 6) from the laser displacement meter 48 to the upper surface 42a of the frame body 42.

In this embodiment, the thickness of the workpiece 11 is calculated by the correction unit 58, but it may also be calculated by a CPU, IC, ASIC (Application Specific Integrated Circuit), etc. installed in the thickness measuring device 46.

The correction unit 58 also calculates a correction value for the cutting feed amount of the cutting unit 8 based on the data on the thickness 11d of the step portion 11c stored in the memory unit 56, as described in Figures 7(A) and 7(B). The control unit 54 controls the Z-axis movement mechanism 20 based on the correction value, and adjusts the cutting feed amount.

Next, a cutting method for the workpiece 11 according to the first embodiment will be described with reference to Figures 3 to 8. Figure 3 is a flow diagram of the cutting method according to the first embodiment for performing edge trimming on the outer periphery of the surface 11a side of the workpiece 11.

First, the laser displacement meter 48 is used to measure a first distance _A1 from the laser displacement meter 48 to the upper surface 42a (upper surface measuring step S10). Fig. 4A is a diagram showing the upper surface measuring step S10.

In the top surface measurement step S10, the chuck table 38 is rotated once while the laser beam is irradiated to one point on the top surface 42a of the frame 42. This allows a first distance _A1 from the laser displacement meter 48 to the top surface 42a to be measured along the path of movement of the laser beam.

The upper surface 42a is substantially flat, but due to factors such as minute irregularities in the circumferential direction and a slight inclination of the rotating shaft 40a, the first distance _A1 has a variation, for example, on the order of μm.

The first distance _A1 is stored in the memory unit 56 together with the rotation angle θ of the chuck table 38. After the top surface measuring step S10, the back surface 11b side of the first type of workpiece 11 (dummy wafer) is held by the holding surface 38a (holding step S20).

Figure 4 (B) shows the holding step S20. After the holding step S20, the cutting edge 16a of the rotating cutting blade 16 is cut into the workpiece 11, and the lower end of the cutting edge 16a is positioned at a predetermined target depth position 13 on the outer periphery of the surface 11a side of the workpiece 11.

In this state, the chuck table 38 is rotated at least 360 degrees around the rotation axis 40a to cut the outer periphery of the surface 11a side with the cutting blade 16a, forming a step portion 11c on the outer periphery of the workpiece 11 (first cutting step S30).

Figure 5 (A) is a partial cross-sectional side view showing the first cutting step S30 (cutting step), and Figure 5 (B) is a perspective view showing the first cutting step S30. After the first cutting step S30, the thickness 11d of the step portion 11c formed in a ring shape along the circumferential direction of the surface 11a is measured (thickness measurement step S40).

Figure 6 shows the thickness measurement step S40. In the thickness measurement step S40, the chuck table 38 is rotated at least 360 degrees around the rotation axis 40a with the laser displacement meter 48 positioned above the step 11c in the same position as in the top surface measurement step S10.

This allows the second distance _A2 from the laser displacement meter 48 to the upper surface 11e of the stepped portion 11c to be measured along the circumferential direction of the workpiece 11. Next, in a thickness measurement step S40, the correction unit 58 calculates the difference between the first distance _A1 and the second distance _A2 , and calculates the thickness 11d of the stepped portion 11c.

Figure 7 (A) is a graph showing the variation in thickness 11d of step portion 11c measured in thickness measurement step S40. In Figure 7 (A), thickness 11d of step portion 11c is shown by a solid line, and target depth position 13 is shown by a dashed line.

In addition, in FIG. 7(A), the height position of the upper surface 42a of the frame body 42 is set as the reference height position (i.e., 0 μm). The target depth position 13 is, for example, 200 μm, and the thickness 11d of the step portion 11c varies from about 1 μm to 10 μm due to factors such as the unevenness and inclination described above.

Therefore, after the thickness measurement step S40, the correction unit 58 calculates a correction value for the cutting feed amount by inverting the data for the thickness 11d of the step portion 11c corresponding to the rotation angle θ with respect to the target depth position 13 (correction value calculation step S50).

Figure 7(B) is a graph showing the correction value. In Figure 7(B), the thickness 11d of the step portion 11c is shown by a dashed line, and the correction value is shown by a solid line. The rest is the same as Figure 7(A). After the correction value calculation step S50, the first type of workpiece 11 (dummy wafer) is removed from the holding surface 38a.

Then, the second type of workpiece 11 (device wafer) is held by suction on the holding surface 38a, and a step portion 11c is formed on the outer periphery of the surface 11a side of the second type of workpiece 11 while adjusting the incision feed amount of the cutting unit 8 according to the rotation angle θ (second cutting step S60).

Figure 8 is a perspective view showing the second cutting step S60. In the second cutting step S60, the surface 11a side is cut while adjusting the infeed amount using a correction value corresponding to the rotation angle θ, so that the variation in thickness 11d of the step portion 11c of the workpiece 11 can be reduced.

The correction value is obtained by actually performing edge trimming on a dummy wafer. Therefore, the correction value more accurately reflects the variation in thickness 11d of step portion 11c, including stress during cutting, compared to when the cutting feed amount is adjusted based only on the variation in height of surface 11a and holding surface 38a before cutting. Therefore, in the second cutting step S60, the variation in thickness 11d of step portion 11c can be effectively reduced.

Next, a second embodiment will be described. In the second embodiment, the above-mentioned cutting device 2 is used, but edge trimming is performed on a second type of workpiece 11 (device wafer) without using a first type of workpiece 11 (dummy wafer).

Fig. 9 is a flow diagram of the cutting method according to the second embodiment. In the second embodiment, first, in the same manner as in Fig. 4(A), a first distance _A1 from the laser displacement meter 48 to the upper surface 42a is measured along the circumferential direction of the upper surface 42a (upper surface measurement step S10).

After the top surface measurement step S10, the back surface 11b side of the second type of workpiece 11 (device wafer) is held by the holding surface 38a (holding step S20) in the same manner as in FIG. 4(B).

After the holding step S20, the cutting edge 16a of the rotating cutting blade 16 is cut into the workpiece 11, and the lower end of the cutting edge 16a is positioned at a provisional cutting target depth position 19 (see FIG. 10(A)) that is shallower (i.e., located above) than the predetermined target depth position 13 on the outer periphery of the surface 11a side of the workpiece 11.

The provisional cutting target depth position 19 is preferably shallower than the target depth position 13 so that the thickness 11d of the step portion 11c can be adjusted in the actual cutting that follows the provisional cutting. For example, if the target depth position 13 is 200 μm, it is set to a position that is a predetermined depth (e.g., 10 μm) shallower than this.

As shown in FIG. 10(A), with the lower end of the cutting edge 16a of the rotating cutting blade 16 positioned at the provisional cutting target depth position 19, the chuck table 38 is rotated at least 360 degrees around the rotation axis 40a to form a provisional cutting step portion 11f on the outer periphery of the workpiece 11 (provisional cutting step S32).

Figure 10 (A) is a diagram showing the provisional cutting step S32. After the provisional cutting step S32, the thickness 11g of the provisionally cut step portion 11f is measured (thickness measurement step S40). Figure 10 (B) is a diagram showing the thickness measurement step S40.

In the thickness measurement step S40, first, the chuck table 38 is rotated at least 360 degrees around the rotation axis 40a with the laser displacement meter 48 placed in the same position as in the top surface measurement step S10.

This measures a third distance _A3 from the laser displacement meter 48 to the top surface 11h of the provisionally cut step portion 11f along the circumferential direction of the workpiece 11. Next, the correction unit 58 calculates the difference between the first distance _A1 and the third distance A3 described above, thereby calculating the thickness _11g of the provisionally cut step portion 11f. The thickness 11g of the provisionally cut step portion 11f may also vary due to factors such as the unevenness and inclination described above.

Therefore, after the thickness measurement step S40, the correction unit 58 calculates a correction value for the cutting feed amount by inverting the data for the thickness 11g corresponding to the rotation angle θ with respect to the provisional cutting target depth position 19, in the same manner as in FIG. 7(B) (correction value calculation step S50).

After the correction value calculation step S50, the cutting edge 16a of the rotating cutting blade 16 is cut into the provisional cutting step 11f, and the lower end of the cutting edge 16a is positioned at a predetermined target depth position 13 on the outer periphery of the surface 11a side. In this state, the chuck table 38 is rotated at least 360 degrees around the rotation axis 40a to form a step 11c on the outer periphery of the workpiece 11 (main cutting step S62).

Figure 9 (C) shows the main cutting step S42. In the main cutting step S42, a step portion 11c having a thickness 11d is formed on the outer periphery of the surface 11a side by cutting to the target depth position 13.

In the second embodiment, the correction value for the infeed amount can be obtained through the top surface measurement step S10 and the correction value calculation step S50. Therefore, there is an advantage in that it is not necessary to use the first type of workpiece 11 (dummy wafer).

Also, in the second embodiment, by adjusting the infeed amount when processing the second type of workpiece 11 (device wafer), the variation in thickness 11d of the step portion 11c of the workpiece 11 can be reduced.

In addition, since the correction value is obtained by the provisional cutting step S32, the correction value more accurately reflects the variation in thickness 11d of the step portion 11c, including the stress during cutting, compared to the case where the infeed amount is adjusted based on the variation in height of the surface 11a or the holding surface 38a before cutting. Therefore, the variation in thickness 11d of the step portion 11c can be effectively reduced.

The structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. For example, the above-described cutting device 2 and cutting method can be realized even if the thickness measuring device 46 is equipped with a displacement meter of another type, such as an ultrasonic type, instead of the above-described laser displacement meter 48.

The workpiece 11 is not limited to a single wafer. The workpiece 11 may be a laminated wafer in which two disk-shaped wafers are bonded together. The laminated wafer is, for example, a first laminated wafer in which a carrier wafer and a dummy wafer are bonded together, or a second laminated wafer in which a carrier wafer and a device wafer are bonded together.

When the above-mentioned cutting method is applied to the stacked wafers, the cutting depth of the cutting edge 16a of the cutting blade 16 can be precisely adjusted to the joint between the upper and lower wafers, so that the outer periphery of only the upper wafer (dummy wafer or device wafer) can be removed by cutting without cutting the outer periphery of the lower wafer (carrier wafer).

2: cutting device, 4: base, 6: cover, 6a: front surface, 8: cutting unit, 10: spindle housing, 12: spindle, 14: rotation drive source, 11: workpiece, 11a: front surface, 11b: back surface, 11c: step portion, 11d, 11g: thickness, 11e, 11h: upper surface, 11f: provisional cutting step portion, 13: target depth position, 15: planned division line, 17: device, 16: cutting blade, 16a: cutting edge, 19: provisional cutting target depth position, 20: Z-axis movement mechanism 22, 32: guide rail, 24, 34: ball screw, 26, 36: rotation drive source 28: Y-axis movement mechanism, 30: Y-axis movement plate 38: chuck table, 38a: holding surface, 40: rotation mechanism, 40a: rotation shaft 42: frame, 42a: upper surface 44: porous plate, 44a: upper surface 46: thickness gauge, 48: laser displacement meter 50: cassette table, 52: display device 54: control unit, 56: memory unit, 58: correction unit _A1 : first distance, _A2 : second distance, _A3 : third distance, θ: rotation angle

Claims (4)

A cutting device for cutting an outer periphery on a front surface side of a workpiece having outer peripheries on a front surface side and a back surface side, the outer periphery being chamfered, and forming an annular step portion on the front surface side,
a chuck table having a holding surface for holding a back side of the workpiece, the chuck table being rotatable about a predetermined rotation axis while holding the workpiece on the holding surface;
a cutting unit having a spindle to which a cutting blade is attached at one end, the cutting blade being attached to the spindle to cut the outer periphery of the front surface side to form the step portion;
a thickness measuring device having a displacement meter and a processor , measuring a first distance from the displacement meter to an upper surface of an outer periphery of the chuck table and a second distance from the displacement meter to an upper surface of the step portion of the workpiece with the displacement meter, and measuring a thickness of the step portion by calculating a difference between the first distance and the second distance ;
a control unit for controlling the chuck table, the cutting unit, and the thickness measuring device;
The control unit
a storage unit that stores a rotation angle of the chuck table and a thickness of the step portion corresponding to the rotation angle;
a correction unit that calculates a correction value for the cutting feed amount of the cutting unit during cutting based on the thickness of the step portion calculated by the thickness measuring device, the data on the thickness of the step portion relative to a reference height position stored in the memory unit, and a deviation between a predetermined target depth position relative to the reference height position;
having
The control unit uses the correction value to adjust the cutting feed amount of the cutting unit, thereby reducing the variation in thickness of an annular step portion in a workpiece other than the workpiece, or the variation in thickness of the step portion in the workpiece. The cutting device according to claim 1, characterized in that the displacement meter is a laser displacement meter. A cutting method for forming an annular step portion on a front surface side of a workpiece having a chamfered outer periphery on each of a front surface side and a back surface side, by cutting the front surface side of the workpiece using a cutting device including a chuck table and a cutting unit having a cutting blade attached thereto, the method comprising the steps of:
an upper surface measuring step of measuring a first distance from the displacement meter to an upper surface of an outer periphery of the chuck table by the displacement meter;
a holding step of holding the back side of the workpiece on a holding surface of the chuck table;
a cutting step of positioning a lower end of the cutting blade at a predetermined target depth position in the outer circumferential portion after the holding step, and rotating the chuck table at least 360 degrees around a predetermined rotation axis to form the step portion on the front surface side;
a thickness measuring step of measuring a thickness of the step portion along a circumferential direction of the workpiece by using a thickness measuring device having a displacement meter disposed above the step portion and a processor , the thickness measuring device including a displacement meter and a processor, the thickness measuring device calculating a difference between a second distance measured by the displacement meter to an upper surface of the step portion of the workpiece and the first distance, by rotating the chuck table around the predetermined rotation axis of the workpiece at least 360 degrees after the cutting step;
a correction value calculation step of calculating a correction value for a cutting feed amount of the cutting unit based on a deviation between thickness data of the step portion corresponding to a rotation angle of the chuck table, the thickness data being for a reference height position, and a predetermined target depth position for the reference height position, after the thickness measurement step,
A cutting method characterized by reducing the variation in thickness of an annular step portion in a workpiece different from the workpiece, or the variation in thickness of the step portion in the workpiece, by utilizing the correction value to adjust the cutting feed amount of the cutting unit. A cutting method for forming an annular step portion on a front surface side of a workpiece having a chamfered outer periphery on each of a front surface side and a back surface side, by cutting the front surface side of the workpiece using a cutting device including a chuck table and a cutting unit having a cutting blade attached thereto, the method comprising:
an upper surface measuring step of measuring a first distance from the displacement meter to an upper surface of an outer periphery of the chuck table by the displacement meter;
a holding step of holding the back side of the workpiece on a holding surface of the chuck table;
a provisional cutting step of positioning a lower end of the cutting blade at a provisional cutting target depth position shallower than a predetermined target depth position in the outer circumferential portion and rotating the chuck table at least 360 degrees around a predetermined rotation axis to form a provisional cutting step portion on the front surface side after the holding step;
a thickness measuring step of measuring a thickness of the provisionally cut step portion along the circumferential direction of the workpiece by using a thickness measuring device having a displacement meter arranged above the provisionally cut step portion and a processor, the thickness measuring device including a displacement meter and a processor, the thickness measuring device calculating a difference between a second distance measured by the displacement meter to an upper surface of the step portion of the workpiece and the first distance, by rotating the chuck table of the workpiece at least 360 degrees around the predetermined rotation axis after the provisional cutting step;
a correction value calculation step of calculating a correction value for a cutting feed amount of the cutting unit based on a deviation between thickness data of the provisionally cut step portion corresponding to a rotation angle of the chuck table, the thickness data being for a reference height position, and a predetermined target depth position for the reference height position, after the thickness measurement step;
a main cutting step of, after the correction value calculation step, positioning a lower end of the cutting blade at a position of the predetermined target depth in the outer circumferential portion and rotating the chuck table around the predetermined rotation axis at least 360 degrees of the workpiece to form the step portion on the front surface side,
The cutting method comprises reducing variation in thickness of the step portion in the workpiece by adjusting the infeed amount of the cutting unit using the correction value.

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