Cutting method

Abstract

The present invention provides a cutting method that imparts ultrasonic vibration to a cutting tool to cut a workpiece and reduces excessive wear of the cutting tool. The cutting method cuts a workpiece using a cutting device that has a chuck table that holds the workpiece and a cutting unit that has a cutting tool that cuts the workpiece held by the chuck table and an ultrasonic vibrator that ultrasonically vibrates the cutting tool in a radial direction of the cutting tool. The cutting method has a holding step that holds the workpiece with the chuck table and a cutting step that performs ultrasonic cutting and normal cutting on the same cutting line among a plurality of cutting lines set for the workpiece. The ultrasonic cutting cuts the workpiece with the cutting tool that is ultrasonically vibrated. The normal cutting cuts the workpiece with the cutting tool that is not ultrasonically vibrated.

Description

TECHNICAL FIELD

[0001] The present application relates to a cutting method of cutting a workpiece using a cutting apparatus having a cutting unit including an ultrasonic vibrator. BACKGROUND

[0002] In a case where a plate-shaped workpiece such as a semiconductor wafer is cut along a division line set in a lattice shape on a front surface side of the workpiece, a cutting apparatus is generally used. The cutting apparatus has a cutting unit and a chuck table disposed below the cutting unit.

[0003] The cutting unit includes a cylindrical spindle. A cutting tool having a circular ring-shaped cutting edge is attached to one end portion of the spindle, and a rotary drive source such as a motor is connected to the other end portion of the spindle.

[0004] In a case where the workpiece is cut, first, the back surface side of the workpiece is suction-held by a holding surface of the chuck table so that the front surface side is exposed upward. Then, the workpiece is divided into a plurality of chips by cutting the workpiece with the cutting tool rotating at high speed along each division line.

[0005] In a case where the workpiece is formed of a brittle hard material or a high-hardness material, cutting of the workpiece becomes difficult. Therefore, it is known that the cutting tool is vibrated in the radial direction by applying ultrasonic vibration to the cutting tool and the workpiece is cut (for example, see Patent Document 1).

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-53234

[0007] When the cutting tool is given ultrasonic vibration, the workpiece is easily cut, but the wear of the cutting tool is correspondingly promoted, and thus there is a problem that the life of the cutting tool is shortened and the frequency of replacement of the cutting tool is increased. SUMMARY

[0008] The present application has been made in view of the above-described problems, and has an object to cut a workpiece by applying ultrasonic vibration to a cutting tool and to reduce excessive wear of the cutting tool.

[0009] According to one embodiment of the present application, there is provided a cutting method of cutting a workpiece using a cutting apparatus having a chuck table that holds the workpiece and a cutting unit that has a cutting tool that cuts the workpiece held by the chuck table and an ultrasonic vibrator that ultrasonically vibrates the cutting tool in a radial direction of the cutting tool, the cutting method comprising: a holding step of holding the workpiece by the chuck table; and a cutting step of performing ultrasonic cutting and normal cutting on the same cutting line among a plurality of cutting lines provided in the workpiece, wherein the ultrasonic cutting cuts the workpiece using the cutting tool that is ultrasonically vibrated, and the normal cutting cuts the workpiece using the cutting tool that is not ultrasonically vibrated.

[0010] Preferably, in the cutting step, after the ultrasonic cutting is performed on a portion of the same cutting line, the ultrasonic vibration is stopped, the cutting tool is not moved in an indexing feed direction, and the normal cutting is performed from a position at which the ultrasonic cutting was last performed on the same cutting line.

[0011] In the cutting step of the cutting method according to one embodiment of the present application, ultrasonic cutting and normal cutting are performed on the same cutting line among a plurality of cutting lines provided in the workpiece, wherein the ultrasonic cutting cuts the workpiece using the cutting tool that is ultrasonically vibrated, and the normal cutting cuts the workpiece using the cutting tool that is not ultrasonically vibrated. Thus, in the ultrasonic cutting, the moderate wear promotion of the cutting tool can be maintained and the workpiece can be cut, and in the normal cutting, the excessive wear of the cutting tool can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a perspective view of a cutting apparatus.

[0013] Figure 2 is a partial cross-sectional side view of the cutting apparatus.

[0014] Figure 3 is a view showing a chuck table and the like in the cutting apparatus.

[0015] Figure 4 is a flowchart showing the cutting method.

[0016] Figure 5 is a view showing a cutting sequence in the cutting method in the embodiment.

[0017] Figure 6 is an image of a glass substrate after cutting using the cutting method of the embodiment.

[0018] Figure 7 (A) is an image of a glass substrate after cutting using the cutting method of the first comparative example, Figure 7 (B) is an image of a glass substrate after cutting using the cutting method of the second comparative example.

[0019] Figure 8 is a view showing the cutting sequence in the cutting method of the second embodiment.

[0020] Explanation of Reference Numerals

[0021] 2: cutting device; 4: cutting unit; 6: spindle housing; 8: spindle; 8a: motor mounting portion; 10: screw; 11: workpiece, 11a: front surface; 11b: back surface; 12: cutting tool; 12a: cutting edge; 12b: radial direction; 13: division intended line; 13a: prescribed position; 13b: cutting groove; 14: motor; 14a: rotor; 14b: stator coil; 15: device; 17: dicing tape; 19: frame; 21: frame unit; 16: ultrasonic vibrator; 18: piezoelectric element; 20, 22: electrode plate; 23: glass substrate; 23a: prescribed position; 24: rotary transformer; 26: power receiving portion; 26a: rotor core; 26b: power receiving coil; 28: power supply portion; 28a: stator core; 28b: power supply coil; 32: AC power supply; 32a: control circuit; 34: voltage frequency adjustment unit; 36: power supply unit; 40: chuck table; 40a: holding surface; 42: frame; 42a: recessed portion; 42b: flow path; 44: porous plate; 46: suction source; 48: electromagnetic valve; 50: machining feed unit. DETAILED DESCRIPTION

[0022] An embodiment relating to one mode of the present application will be described with reference to the drawings. Figure 1 is a perspective view of the cutting device 2, Figure 2 is a partially cutaway side view of the cutting device 2, Figure 3 is a view showing the chuck table 40 and the like in the cutting device 2.

[0023] The cutting device 2 has a cutting unit 4 that cuts the workpiece 11. The cutting unit 4 has a cylindrical spindle housing 6 disposed substantially parallel to the Y-axis direction (index feed direction). Inside the spindle housing 6, a portion of a cylindrical spindle 8 is rotatably housed (see Figure 2 ).

[0024] A threaded hole is formed in one end portion of the spindle 8. A cutting tool 12 is mounted to the one end portion of the spindle 8 by a screw 10 fixed to the threaded hole. The cutting tool 12 has a circular ring-shaped cutting edge 12a in the outer peripheral portion. The cutting edge 12a is composed of abrasive grains and a bonding material that fixes the abrasive grains.

[0025] A cylindrical motor mounting portion 8a is provided at the other end portion of the main shaft 8. A rotor 14a of a motor 14 that rotates the main shaft 8 is coupled to the motor mounting portion 8a. The rotor 14a has, for example, a permanent magnet.

[0026] A stator coil 14b fixed to the main shaft housing 6 is separately provided at the outer peripheral side of the rotor 14a. When alternating-current power is supplied to the stator coil 14b from an alternating-current power supply 32 via a control circuit 32a to be described later, the rotor 14a rotates.

[0027] Further, the control circuit 32a adjusts the current supplied to the stator coil 14b. The operation of the control circuit 32a is controlled by a control unit (not shown) of the cutting tool 2. An ultrasonic vibrator 16 that imparts ultrasonic vibrations to the cutting tool 12 is coupled to the side of the motor 14 opposite the motor mounting portion 8a.

[0028] The ultrasonic vibrator 16 has a ring-shaped piezoelectric element 18 polarized in the axial direction of the main shaft 8. The piezoelectric element 18 is formed of a piezoelectric ceramic such as barium titanate, lead zirconate titanate, or lithium tantalate. Ring-shaped electrode plates 20 and 22 are respectively fixed to the polarized surfaces on both sides of the piezoelectric element 18.

[0029] A rotary transformer 24 is coupled to the side of the ultrasonic vibrator 16 opposite the motor 14. The rotary transformer 24 has a cylindrical power receiving portion 26. The power receiving portion 26 includes a rotor core 26a coupled to the main shaft 8 via the ultrasonic vibrator 16, and a power receiving coil 26b wound around the outer peripheral portion of the rotor core 26a.

[0030] A ring-shaped power feeding portion 28 is separately provided on the outer side of the power receiving portion 26 in such a manner as to surround the power receiving portion 26. The power feeding portion 28 includes a ring-shaped stator core 28a provided on the outer peripheral side of the power receiving coil 26b, and a power feeding coil 28b provided on the inner peripheral side surface of the stator core 28a.

[0031] Power is supplied from the alternating-current power supply 32 to the power feeding coil 28b via a voltage frequency adjusting unit 34. The voltage frequency adjusting unit 34 is, for example, a function generator, and the operation of the voltage frequency adjusting unit 34 is controlled by the control unit (not shown) of the cutting tool 2.

[0032] The alternating-current power supply 32 and the voltage frequency adjusting unit 34 constitute a power supply unit 36 that supplies alternating-current power at a prescribed frequency and a prescribed voltage to the power feeding portion 28. When power is supplied to the power feeding coil 28b, an alternating-current voltage is applied to the power receiving coil 26b in a non-contact manner.

[0033] An electrode plate 20 is connected to one end of the power receiving coil 26b, and an electrode plate 22 is connected to the other end of the power receiving coil 26b, so that an alternating voltage applied to the power receiving coil 26b is applied to the electrode plates 20, 22.

[0034] When an alternating voltage of an ultrasonic frequency is applied to the electrode plates 20, 22, the ultrasonic vibrator 16 vibrates in the axial direction of the spindle 8 at the frequency of the ultrasonic wave. The vibration in the axial direction of the spindle 8 is converted into a vibration in the radial direction 12b of the cutting tool 12 at the end portion of the spindle 8, and the cutting tool 12 vibrates in the radial direction 12b at the frequency of the ultrasonic wave, that is, ultrasonic vibration is performed.

[0035] A chuck table 40 is disposed below the cutting unit 4. The chuck table 40 has a frame 42 (see FIG. 2) in a disc shape. A recess 42a in a disc shape is formed in the upper portion of the frame 42, and a porous plate 44 in a disc shape formed of a porous ceramic is fixed in the recess 42a. Figure 3

[0036] The upper surface of the porous plate 44 and the upper surface of the frame 42 are substantially flush with each other, and constitute a holding surface 40a of the chuck table 40. One end of a flow path 42b is connected to the central portion of the recess 42a, and a suction source 46 such as an ejector is connected to the other end of the flow path 42b.

[0037] Further, a solenoid valve 48 is provided between the one end and the other end of the flow path 42b. When the solenoid valve 48 is in an open state, a negative pressure generated by the suction source 46 is transmitted to the porous plate 44 via the flow path 42b, and a negative pressure is generated on the upper surface of the porous plate 44.

[0038] Here, the workpiece 11 held by the holding surface 40a will be described. As shown in FIG. 1, the workpiece 11 in a disc shape is formed of a semiconductor wafer such as silicon, and a plurality of division intended lines 13 (cutting lines) are set in a lattice shape on the front surface 11a side of the workpiece 11. Figure 1

[0039] In each region divided by the plurality of division intended lines 13, a device 15 such as an IC (Integrated Circuit) or an LSI (Large Scale Integration) is formed. However, the kind, material, size, shape, structure, and the like of the workpiece 11 are not limited.

[0040] The workpiece 11 can also be a wafer or a substrate formed of a compound semiconductor (GaN, SiC, or the like) other than silicon, glass, ceramic, resin, metal, or the like. Further, the kind, number, shape, structure, size, arrangement, and the like of the device 15 formed on the workpiece 11 are not limited. The device 15 can also not be formed on the workpiece 11. ​​

[0041] A resin-made dicing tape 17 is attached to the back surface 11b side of the work 11. The dicing tape 17 is circular, and the diameter of the dicing tape 17 is larger than the diameter of the work 11. The work 11 is attached to the central portion of the dicing tape 17, and one face of a ring-shaped frame 19 formed of metal is attached to the outer peripheral portion of the dicing tape 17.

[0042] Thus, a frame unit 21 is constituted in which the work 11 is supported by the frame 19 via the dicing tape 17. Also, in Figure 2 and Figure 3 , the dicing tape 17 and the frame 19 are omitted.

[0043] A θ stage (not shown) that rotates the chuck table 40 about a rotation axis that is substantially parallel to the Z-axis direction (height direction, vertical direction) is provided below the chuck table 40. This θ stage is supported by a machining feed unit 50 (refer to Figure 2 ).

[0044] The machining feed unit 50 is a ball screw type moving mechanism that moves the chuck table 40 and the θ stage in the X-axis direction (machining feed direction). In addition, the X-axis direction, the Y-axis direction, and the Z-axis direction are directions that are perpendicular to one another.

[0045] Next, a machining method in which the work 11 is machined using the cutting apparatus 2 will be described. Figure 4 is a flowchart showing the machining method. First, as shown in Figure 3 , the back surface 11b side of the work 11 is held by the holding face 40a of the chuck table 40 (holding step S10).

[0046] After the holding step S10, the work 11 is machined (machining step S20). In the machining step S20, first, the dividing intended line 13 is detected by a camera unit (not shown), and the orientation of the work 11 is adjusted by the θ stage (not shown) so that one of the dividing intended lines 13 is substantially parallel to the X-axis direction.

[0047] After that, the cutting tool 12 that is rotating at high speed is positioned on the extension line of one of the dividing intended lines 13, and the lower end of the cutting tool 12 is positioned at a height between the back surface 11b and the holding face 40a. Furthermore, the ultrasonic vibrator 16 is caused to operate.

[0048] Next, as shown in Figure 1 , the chuck table 40 is moved in the X-axis direction, and in one of the dividing intended lines 13, from one side to a prescribed position 13a, ultrasonic machining is performed in which the work 11 is machined by the cutting tool 12 that is vibrating at the frequency of the ultrasonic waves. Also, at the time of machining, machining water such as pure water is supplied to the machining point from a machining water supply nozzle.

[0049] After the ultrasonic cutting is performed to the prescribed position 13a, the cutting unit 4 is index-fed by a prescribed length. Then, on the other division predetermined line 13 adjacent to the one division predetermined line 13 on which the cutting groove 13b is formed in the Y-axis direction, the ultrasonic cutting is similarly performed from the side of the other division predetermined line 13 to the prescribed position 13a.

[0050] Similarly, after the cutting groove 13b is formed by the ultrasonic cutting along all of the division predetermined lines 13 in one direction, the power supply to the ultrasonic vibrator 16 is stopped, and the rotating cutting tool 12 is lowered to cut into the prescribed position 13a of the division predetermined line 13 on which the cutting is first performed.

[0051] Then, from the prescribed position 13a to the other side of the division predetermined line 13, the following normal cutting is performed: the cutting tool 12 in a state not vibrating at the frequency of the ultrasonic waves cuts the workpiece 11. Similarly, for the remaining division predetermined lines 13, the normal cutting is performed from the prescribed position 13a to the other side of the division predetermined line 13.

[0052] After the cutting groove 13b is formed along all of the division predetermined lines 13 in one direction, the chuck table 40 is rotated by 90 degrees so that the division predetermined line 13 on which the cutting is not performed is substantially parallel to the X-axis direction. Then, the ultrasonic cutting and the normal cutting are similarly performed on all of the division predetermined lines 13 on which the cutting is not performed. Thus, the workpiece 11 is divided into a plurality of chips.

[0053] In the cutting step S20 of the present embodiment, the cutting groove 13b is formed along each division predetermined line 13 by performing the ultrasonic cutting and the normal cutting on the same division predetermined line 13 (the same cutting line). In addition, the same division predetermined line 13 (the same cutting line) refers to one division predetermined line 13 (one cutting line) that is continuously set in a straight line shape.

[0054] In the ultrasonic cutting, the moderate wear promotion of the cutting tool 12 can be maintained and the workpiece 11 is cut. On the contrary, in the normal cutting, since the cutting tool 12 is not vibrated, the excessive wear of the cutting tool 12 can be suppressed. Thus, the moderate wear promotion of the cutting tool 12 can be maintained and the excessive wear of the cutting tool 12 can be suppressed.

[0055]

EMBODIMENT

[0056] Next, the embodiment will be described. Figure 5 is a view showing the cutting sequence in the cutting method in the embodiment, Figure 6 is an image of a glass substrate 23 (made of sodium glass) after the cutting is performed by the cutting method of the embodiment. In addition, in Figure 6 , the portion on which the cutting groove is not formed is omitted.

[0057] In this embodiment, a square, plate-shaped glass substrate 23 with one side of 100 mm, another side of 100 mm, and a thickness of 0.5 mm is used. Forty cutting lines are set along one side of the glass substrate 23. In addition, each cutting line is discretely set along the other side of the glass substrate 23.

[0058] In particular, in this embodiment, ultrasonic cutting is performed from one end of an edge to a predetermined position 23a located at 15mm, in the order of #1 to #40 (dashed lines). Then, normal cutting is performed from the predetermined position 23a to the other end of an edge, in the order of #41 to #80 (dashed lines). Figure 5 ).

[0059] In addition, the cutting lines shown by #1 and #41 are the same cutting lines, and the cutting lines shown by #N and #N+40 are also the same cutting lines (in addition, N is a natural number of 2 or more and 40 or less).

[0060] During cutting, the cutting tool 12 rotates at 20,000 rpm, and the chuck stage 40, which holds the glass substrate 23, performs a machining feed at 20 mm / s. Additionally, during cutting, pure water (not shown) is supplied to the machining point at a rate of 2.5 L / min from the cutting water supply nozzle.

[0061] Thus, a cutting groove with a depth of 430 μm is formed on each cutting line (see reference). Figure 6 In this embodiment, when 40 cutting grooves were formed, the cutting edge 12a of the cutting tool 12 consumed 0.9 μm in the radial direction 12b.

[0062] Figure 7 Image (A) is an image of the glass substrate 23 after cutting using the cutting method of the first comparative example. Additionally, in Figure 7 In (A), the portion where the cutting grooves are not formed is omitted. In the first comparative example, normal cutting from one end of one side of the glass substrate 23 to the other end was performed in the order of #1 to #40, thereby discretely forming 40 cutting grooves in the direction of the other side of the glass substrate 23.

[0063] The rotational speed of the cutting tool 12 and the machining feed rate of the chuck table 40 are the same as in the embodiment described above, and cutting water is also provided in the same manner. When the formation of 40 cutting grooves is completed, the cutting edge 12a of the cutting tool 12 is consumed by 0.5 μm in the radial direction 12b.

[0064] The consumption of cutting edge 12a is reduced compared to the embodiment, but according to Figure 7 (A) and Figure 6It is understood from a comparison between (A) of the first comparative example and (A) of the embodiment that a significant processing failure occurs in the rear of the cutting sequence in the first comparative example. The processing failure is shown in black in (A) of the first comparative example. It is presumed that the cause of the processing failure is a clogging of abrasive grains due to an inadequate consumption of the bonding material. Figure 7

[0065] Figure 7 (B) of the first comparative example is an image of the glass substrate 23 after cutting using the cutting method of the first comparative example. In addition, in (B) of the first comparative example, a portion in which the cutting groove is not formed is omitted. In the first comparative example, ultrasonic cutting is performed from one end of one edge of the glass substrate 23 to the other end in the order of #1 to #40, whereby 40 cutting grooves are discretely formed in the direction of the other edge of the glass substrate 23. Figure 7

[0066] The rotational speed of the cutting tool 12 and the machining feed speed of the chuck table 40 are the same as in the above-described embodiment, and cutting water is also provided in the same manner. Figure 7 Figure 6 It is understood from a comparison between (B) of the second comparative example and (A) of the embodiment that almost no processing failure occurs in the second comparative example. However, the consumption amount of the cutting edge 12a is significantly increased compared to the embodiment.

[0067] Specifically, at the end of the formation of the 40 cutting grooves, the cutting edge 12a of the cutting tool 12 is consumed by 2.55 μm in the radial direction 12b. If the first comparative example and the second comparative example are compared with the embodiment, it can be said that in the cutting method of the embodiment, the moderate wear promotion of the cutting tool 12 can be maintained and the excessive wear of the cutting tool 12 can be suppressed.

[0068] Next, the second embodiment will be described. Figure 8 is a view showing the cutting sequence in the cutting method of the second embodiment. In the second embodiment, after cutting is performed from one end to the other end of one cutting line, indexing feed is performed, and cutting is performed from one end to the other end of an adjacent one cutting line.

[0069] However, in the second embodiment, first, as shown by the dashed line, ultrasonic cutting is performed from one end of the glass substrate 23 to a prescribed position 23a (to a portion on the same cutting line) and then the ultrasonic cutting is stopped.

[0070] Then, without moving the cutting tool 12 in the Y-axis direction, as shown by the single-dot chain line, normal cutting is performed from the prescribed position 23a (a position at which ultrasonic cutting was last performed on the same cutting line) to the other end of the glass substrate 23.

[0071] ​​​Thus, by performing the ultrasonic cutting and the normal cutting on the same cutting line, in the ultrasonic cutting, the moderate wear promotion of the cutting tool 12 can be maintained and the glass substrate 23 is cut, and in the normal cutting, the excessive wear of the cutting tool 12 can be suppressed.

[0072] Further, the configuration, method, and the like of the above-described embodiments can be appropriately changed and implemented as long as the range of the object of the present application is not deviated. For example, the above-described workpiece 11 can be cut according to the cutting method of the second embodiment.

Claims

1. A cutting method of cutting a workpiece using a cutting apparatus, the cutting apparatus having: a chuck table that holds the workpiece; and a cutting unit that has a cutting tool that cuts the workpiece held by the chuck table, and an ultrasonic vibrator that ultrasonically vibrates the cutting tool in a radial direction of the cutting tool, characterized in that the cutting method has steps of: a holding step of holding the workpiece by the chuck table; and a cutting step of performing ultrasonic cutting and normal cutting on the same cutting line among a plurality of cutting lines set for the workpiece, wherein the ultrasonic cutting cuts the workpiece by the cutting tool that is ultrasonically vibrated, and the normal cutting cuts the workpiece by the cutting tool that is not ultrasonically vibrated, in the cutting step, the ultrasonic cutting is performed in a first region from a first position to a prescribed position in a length direction of the same cutting line, and the normal cutting is performed in a second region different from the first region in the length direction of the same cutting line and from the prescribed position to a second position.

2. The cutting method according to claim 1, characterized in that in the cutting step, after the ultrasonic cutting is performed in the first region from the first position to the prescribed position in the length direction of the same cutting line, ultrasonic vibration is stopped, the cutting tool is not moved in an indexing feed direction, and the normal cutting is performed in the second region different from the first region in the length direction of the same cutting line and from the prescribed position to the second position at which the ultrasonic cutting was last performed.

3. The cutting method according to claim 1, characterized in that in the cutting step, a cutting groove formed by the ultrasonic cutting and the normal cutting has the same depth.

4. The cutting method according to any one of claims 1 to 3, characterized in that the workpiece is a glass substrate.

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