Cutting method for workpieces

Abstract

Edge trimming reduces the unevenness at the bottom of the annular stepped portion formed on the outer circumference of the workpiece. [Solution] The present invention provides a method for cutting a workpiece, comprising: a first cutting step in which a cutting blade attached to the tip of a spindle whose longitudinal direction is aligned with the holding surface is used to cut the outer circumference of one surface of a workpiece held on the holding surface of a chuck table to form a stepped portion, and a second cutting step in which, after the first cutting step, the bottom of the stepped portion is cut by moving the chuck table and the cutting blade relative to each other, wherein the second cutting step includes moving the chuck table and the cutting blade relative to each other along the longitudinal direction of the spindle while maintaining the height position of the spindle relative to the chuck table.

Description

Technical Field

[0001] The present invention relates to a cutting method for a workpiece, which removes a chamfer portion on one surface of the workpiece having a chamfer portion on the outer peripheral portion of one surface and forms an annular stepped portion on the outer peripheral portion of the workpiece.

Background Art

[0002] When manufacturing semiconductor device chips, for example, the wafer (i.e., the workpiece) is divided into a plurality of semiconductor device chips by cutting the wafer along a plurality of division planned lines set in a grid pattern on the surface of the wafer.

[0003] Before dividing the wafer in this way, devices such as ICs (Integrated Circuits) are formed in each region partitioned by a plurality of division planned lines, and then the back surface of the wafer is polished to thin the wafer to a predetermined thickness, and then the wafer is divided.

[0004] By the way, when chamfer portions are formed on the outer peripheral portions of the front and back surfaces of the wafer, if the back surface of the wafer is polished to thin the thickness of the wafer to less than half of that before polishing, a so-called sharp edge (also referred to as a knife edge) is formed on the outer peripheral edge of the front surface of the wafer. The sharp edge may induce breakage of the wafer.

[0005] Therefore, in order to prevent breakage of the wafer caused by the sharp edge, before polishing the back surface, the chamfer portion on the front surface of the wafer is removed by cutting the outer peripheral portion of the front surface of the wafer with a cutting blade (i.e., performing so-called edge trimming), and then, a technique of polishing the back surface of the wafer is known (see, for example, Patent Document 1).

[0006] An annular stepped portion is formed on the outer peripheral portion of the front surface of the wafer by edge trimming, and cutting marks are usually formed at the bottom of this stepped portion due to cutting with a cutting blade. Note that the cutting marks formed at the bottom of the stepped portion include periodic irregularities in the radial direction of the wafer.

[0007] If cutting marks containing such irregularities exist at the bottom of a stepped section, for example, when measuring the distance from the measuring instrument to the bottom of the stepped section using an optical method and calculating the distance from the bottom of the stepped section to the back surface of the wafer (i.e., the remaining thickness of the outer edge of the wafer), the measurement light may not be properly reflected at the bottom of the stepped section. In this case, problems such as obtaining excessive measurement errors or being unable to measure at all may occur. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2000-173961 [Overview of the project] [Problems that the invention aims to solve]

[0009] This invention has been made in view of the aforementioned problems, and aims to reduce the unevenness at the bottom of the annular stepped portion formed on the outer circumference of a workpiece by edge trimming. [Means for solving the problem]

[0010] According to one aspect of the present invention, a method for cutting a workpiece having a chamfered portion on the outer circumference of one surface of the workpiece is provided, which removes the chamfered portion on one surface of the workpiece and forms an annular stepped portion on the outer circumference of the one surface, comprising: a first cutting step of cutting the outer circumference of one surface of the workpiece to form the stepped portion by cutting into the chamfered portion of one surface of the workpiece held on the holding surface of the chuck table with a cutting blade mounted on the tip of a spindle whose longitudinal direction is aligned with the holding surface, and rotating the chuck table; and a second cutting step of cutting the bottom of the stepped portion by moving the chuck table and the cutting blade relative to each other after the first cutting step, wherein the second cutting step includes moving the chuck table and the cutting blade relative to each other along the longitudinal direction of the spindle while maintaining the height position of the spindle relative to the chuck table.

[0011] Preferably, in the second cutting step, the chuck table is rotated while the chuck table and the cutting blade are moved relative to each other.

[0012] Preferably, the workpiece cutting method further includes a third cutting step in which, while maintaining the height position of the spindle relative to the chuck table, the cutting blade is moved relative to the chuck table in the opposite direction to the direction of movement of the cutting blade relative to the chuck table in the second cutting step, and the second cutting step and the third cutting step are repeated multiple times.

[0013] Preferably, the method for cutting a workpiece further comprises a chuck table rotation step, in which the chuck table is rotated by a predetermined angle after the second cutting step, and a third cutting step, in which, while maintaining the height position of the spindle relative to the chuck table, the cutting blade is moved relative to the chuck table in the opposite direction to the direction of movement of the cutting blade relative to the chuck table in the second cutting step.

[0014] Preferably, the second cutting step, the chuck table rotation step after the second cutting step, and the third cutting step after the chuck table rotation step are repeated in this order.

[0015] Preferably, the workpiece comprises a lower wafer and an upper wafer having chamfered portions on the outer periphery of both sides and being fixed on top of the lower wafer, wherein the first cutting step forms the stepped portion on the outer periphery of the upper wafer, and the second cutting step cuts the bottom of the stepped portion of the upper wafer.

[0016] Preferably, the workpiece cutting method further includes a measurement step of irradiating the bottom of the stepped portion that has been subjected to the second cutting step with measuring light from a sensor head, and measuring the distance from the other side of the workpiece located opposite to the one side to the bottom of the stepped portion.

[0017] Preferably, the method for cutting a workpiece further comprises: an additional first cutting step after the second cutting step, in which the cutting blade is driven into the bottom of the stepped portion and the chuck table is rotated to deepen the stepped portion, thereby forming the stepped portion with the outer peripheral side surface of the upper wafer, the outer peripheral side surface of the lower wafer, and the outer peripheral portion of the lower wafer; and an additional second cutting step after the additional first cutting step, in which the outer peripheral portion of the lower wafer constituting the stepped portion is cut.

[0018] Preferably, the method for cutting the workpiece further includes an imaging step of imaging the bottom of the stepped portion that has undergone the additional second cutting step. [Effects of the Invention]

[0019] In a workpiece cutting method according to one aspect of the present invention, an annular step is formed on the outer circumference of one surface of the workpiece in a first cutting step, and then the bottom of the step is cut in a second cutting step. In particular, the second cutting step includes moving the cutting blade along the longitudinal direction of the spindle while maintaining the height position of the spindle relative to the chuck table, so that the irregularities formed at the bottom of the step can be reduced. [Brief explanation of the drawing]

[0020] [Figure 1] It is a flow chart of a cutting method. [Figure 2] FIG. 2(A) is a side view of the wafer, and FIG. 2(B) is a top view of the wafer. [Figure 3] FIG. 3(A) is a partial cross-sectional side view showing the first cutting step, and FIG. 3(B) is a top view showing the first cutting step. [Figure 4] FIG. 4(A) is a partial cross-sectional side view showing the start of the second cutting step, and FIG. 4(B) is a top view showing the start of the second cutting step. [Figure 5] FIG. 5(A) is a partial cross-sectional side view showing the end of the second cutting step, and FIG. 5(B) is a top view showing the end of the second cutting step. [Figure 6] FIG. 6(A) is a schematic top view of the wafer after the second cutting step, FIG. 6(B) is a schematic cross-sectional view taken along A-A of FIG. 6(A), and FIG. 6(C) is a schematic cross-sectional view taken along B-B of FIG. 6(A). [Figure 7] It is a partial cross-sectional side view showing the measurement step. [Figure 8] FIG. 8(A) is a partial cross-sectional side view showing the start of the second cutting step according to the second embodiment, and FIG. 8(B) is a top view showing the start of the second cutting step according to the second embodiment. [Figure 9] FIG. 9(A) is a top view showing a first example of the wafer after the second cutting step according to the second embodiment, and FIG. 9(B) is a top view showing a second example of the wafer after the second cutting step according to the second embodiment. [Figure 10] It is a flow chart of a cutting method according to the third embodiment. [Figure 11] FIG. 1 (A) is a top view showing a first example of the wafer cut by the cutting method according to the third embodiment, and FIG. 11(B) is a top view showing a second example of the wafer cut by the cutting method according to the third embodiment. [Figure 12] It is a flow chart of a cutting method according to the fourth embodiment. [Figure 13]Figure 13(A) is a top view showing a first example of a wafer cut using the cutting method of the fourth embodiment, and Figure 13(B) is a top view showing a second example of a wafer cut using the cutting method of the fourth embodiment. [Figure 14] This is a flowchart of the cutting method according to the fifth embodiment. [Figure 15] Figure 15(A) is a side view of the bonded wafer, and Figure 15(B) is a top view of the bonded wafer. [Figure 16] Figure 16(A) is a partial cross-sectional side view showing the first cutting process, and Figure 16(B) is a partial cross-sectional side view showing the second cutting process. [Figure 17] This is a partial cross-sectional side view showing the measurement process. [Figure 18] Figure 18(A) is a partial cross-sectional side view showing an additional first cutting process, and Figure 18(B) is a partial cross-sectional side view showing an additional second cutting process. [Figure 19] Figure 19(A) is a partial cross-sectional side view showing the imaging process, Figure 19(B) is a schematic diagram of an image obtained in the imaging process of the fifth embodiment, and Figure 19(C) is a schematic diagram of an image obtained in a conventional imaging process. [Modes for carrying out the invention]

[0021] (First Embodiment) An embodiment according to one aspect of the present invention will be described with reference to the attached drawings. Figure 1 is a flow chart of a cutting method for wafer 11 (see Figures 2(A) and 2(B)). In the first embodiment, the first cutting step S10, the second cutting step S20, and the measurement step S30 are performed in that order.

[0022] First, the disc-shaped wafer (workpiece) 11 will be described with reference to Figures 2(A) and 2(B). Figure 2(A) is a side view of the wafer 11, and Figure 2(B) is a top view of the wafer 11.

[0023] The wafer 11 has a front surface (i.e., one side) 11a and a back surface (i.e., the other side) 11b. The front surface 11a and the back surface 11b are located on opposite sides in the thickness direction 11c of the wafer 11. The wafer 11 has, for example, a diameter of about 300 mm (i.e., 12 inches) and a thickness of about 775 μm.

[0024] Multiple division lines (not shown) are arranged in a grid pattern on the surface 11a of the wafer 11. Devices such as ICs (not shown) are formed in each rectangular region demarcated by the multiple division lines. The surface 11a has a chamfered portion 11a1 on its outer edge, and the back surface 11b similarly has a chamfered portion 11b1 on its outer edge. The chamfered portions 11a1 and 11b1 are also called bevels.

[0025] In the thickness direction 11c of the wafer 11, between the chamfered portion 11a1 of the surface 11a and the chamfered portion 11b1 of the back surface 11b, there exists an edge 11d that defines the outermost periphery of the wafer 11 when viewed from above.

[0026] In this embodiment, a cutting device 2 (see Figures 3(A) and 3(B)) is used to remove the chamfered portion 11a1 of the surface 11a and to form an annular stepped portion 11e (see Figures 4(A) to 5(B)) on the outer circumference of the wafer 11.

[0027] Next, we will briefly explain the cutting device 2 with reference to Figure 3(A). The X, Y, and Z axes shown in Figure 3(A) are orthogonal to each other. The X axis is approximately parallel to the machining feed direction of the cutting device 2, and the Y axis is approximately parallel to the indexing feed direction of the cutting device 2. The Z axis is approximately parallel to the vertical direction.

[0028] Figure 3(A) shows the +X, +Y, and +Z directions. However, the X-axis direction includes the +X and -X directions, which are parallel to the X-axis and opposite to each other. Similarly, the Y-axis direction includes the +Y and -Y directions, which are parallel to the Y-axis and opposite to each other, and the Z-axis direction includes the +Z and -Z directions, which are parallel to the Z-axis and opposite to each other.

[0029] As shown in Figure 3(A), the cutting device 2 has a disc-shaped chuck table 4. The chuck table 4 has a disc-shaped frame 6 made of a non-porous hard resin. A disc-shaped recess 6a is provided in the center of the upper surface of the frame 6. A disc-shaped porous plate 8 made of porous ceramics is fixed to the recess 6a using an adhesive or the like.

[0030] The annular upper surface of the frame 6 and the upper surface of the porous plate 8 constitute a holding surface 4a that holds the wafer 11 by suction. The holding surface 4a is substantially flush and arranged substantially parallel to the XY plane. A channel is formed in the frame 6 for transmitting negative pressure to the porous plate 8.

[0031] A vacuum generating device (not shown), such as a vacuum pump, is connected to the flow path of the frame 6. The wafer 11 is held in place by suction due to the negative pressure transmitted from the vacuum generating device to the holding surface 4a. Note that the chuck table 4 is not limited to this example.

[0032] The chuck table 4 may not have a porous plate 8, but may have the frame 6 described above having an outer diameter approximately the same as the outer diameter of the wafer 11. In this case, an annular suction groove for supplying negative pressure is provided on the annular upper surface of the frame 6, and the wafer 11 is held in place by the negative pressure transmitted to the annular suction groove.

[0033] A rotating shaft 10 is connected to the bottom of the chuck table 4. The longitudinal direction of the rotating shaft 10 is approximately parallel to the Z-axis. When power is transmitted to the rotating shaft 10 from a rotational drive source (not shown), such as a motor, the chuck table 4 rotates around the rotating shaft 10.

[0034] Furthermore, by adjusting the motor's operation, the rotation direction of the chuck table 4 can be set to either clockwise or counterclockwise when viewed from above, and the rotation speed of the chuck table 4 can be set to any desired value.

[0035] The chuck table 4 and the rotational drive source are supported by an X-axis movement mechanism (not shown) having a ball screw, servo motor, etc., and are configured to move along the X-axis. The X-axis movement mechanism is also called a machining feed mechanism.

[0036] A cutting unit 12 is provided above the holding surface 4a of the chuck table 4. The cutting unit 12 has a spindle housing 14 whose longitudinal portion is arranged along the Y-axis. A portion of a cylindrical spindle 16 is rotatably housed in the spindle housing 14 by air bearings (i.e., hydrostatic air bearings).

[0037] The longitudinal direction of the spindle 16 is positioned approximately parallel to the Y-axis. In other words, the longitudinal direction of the spindle 16 is aligned with the holding surface 4a. A stator (not shown) is provided inside the spindle housing 14, and a rotor, which together with the stator constitutes a motor, is provided on a part of the spindle 16.

[0038] The tip of the spindle 16 protrudes outside the spindle housing 14, and a cutting blade 18 having an annular cutting edge is attached to the tip of the spindle 16 using a blade mount, fixing nut, etc.

[0039] The cutting blade 18 has abrasive grains made of diamond or the like, and a bonding material for fixing the abrasive grains. The cutting blade 18 rotates around the spindle 16 as the spindle 16 rotates.

[0040] A Z-axis movement mechanism (not shown) having a ball screw, servo motor, etc., is attached to the spindle housing 14. The Z-axis movement mechanism allows the cutting unit 12 to move along the Z axis. This adjusts the cutting depth of the cutting blade 18 in relation to the wafer 11. The Z-axis movement mechanism is also called a cutting feed mechanism.

[0041] The Z-axis movement mechanism is configured to move along the Y-axis by a Y-axis movement mechanism (not shown) that includes a ball screw, a servo motor, etc. The Y-axis movement mechanism allows the cutting unit 12 to move along the Y-axis. In other words, the cutting blade 18 can be moved along the Y-axis. The Y-axis movement mechanism is also called an indexing feed mechanism.

[0042] In this embodiment, a sensor head 22 (see Figure 7) of a thickness measuring instrument 20, which measures the thickness of the outer periphery of the wafer 11 non-contactually by an optical method, is fixed to one side of the spindle housing 14 in the X-axis direction.

[0043] Therefore, the sensor head 22 is movable along the Y and Z axes together with the spindle housing 14. However, the sensor head 22 may also be movable along the X, Y, and Z axes independently of the spindle housing 14.

[0044] The thickness measuring instrument 20 of this embodiment is a spectral interference type thickness measuring instrument and includes an SLD (Super Luminescent Diode) light source (not shown) that emits light in the near-infrared wavelength band that can penetrate the wafer 11, a sensor head 22, a spectrometer (not shown), a waveform analysis unit (not shown) which is realized by executing a program on a processor, and the like.

[0045] In this embodiment, a microscope camera 30 (see Figure 19(A)) that uses visible light to image the wafer 11 is fixed to the other side of the spindle housing 14 in the X-axis direction. The microscope camera 30 is also movable along the Y-axis and Z-axis together with the spindle housing 14.

[0046] However, the microscope camera 30 may be movable along the X, Y, and Z axes independently of the spindle housing 14. Next, each step shown in Figure 1 will be described with reference to Figures 3(A) to 7.

[0047] Figure 3(A) is a partial cross-sectional side view showing the first cutting process S10, and Figure 3(B) is a top view showing the first cutting process S10. In the first cutting process S10, the wafer 11 is first held by suction on the holding surface 4a of the chuck table 4.

[0048] Next, the lower end of the cutting blade 18, which rotates at high speed around the spindle 16 as its axis of rotation, is positioned at a height between the surface 11a and the back surface 11b. For example, the rotational speed of the spindle 16 is set to 30,000 rpm, and the lower end of the cutting blade 18 is set to a predetermined value of several tens of micrometers to 100 micrometers from the surface 11a.

[0049] Then, the chuck table 4 is moved along the X-axis relative to the cutting unit 12. Specifically, the chuck table 4 is moved along the X-axis until, in a top view, the extension of the rotation center 16a of the spindle 16 in the Y-axis direction intersects with the rotation center 10a of the rotation axis 10, thereby cutting the cutting blade 18 into the chamfered portion 11a1 of the wafer 11.

[0050] If the cutting unit 12 is movable along the X-axis, the cutting blade 18 may make a cut into the chamfered portion 11a1 by moving the cutting unit 12 along the X-axis.

[0051] Furthermore, this is not limited to movement of the chuck table 4 or the cutting unit 12 in the X-axis direction, but may also be achieved by moving the chuck table 4 and the cutting unit 12 relatively along the Z-axis (i.e., lowering the cutting unit 12 along the Z-axis, or raising the chuck table 4 along the Z-axis).

[0052] In any case, the cutting blade 18 is used to cut into the chamfered portion 11a1 of the surface 11a, and the chuck table 4 is rotated at a predetermined rotational speed (for example, 5° / s) around the rotation axis 10 at least one rotation, thereby cutting the outer periphery of the surface 11a of the wafer 11 to form a stepped portion 11e (see Figures 4(A) and 4(B)).

[0053] The stepped portion 11e is defined by a cylindrical outer peripheral surface that is substantially perpendicular to the surface 11a, and an annular bottom portion (i.e., the bottom portion 11e1 described later) that is connected to the outer peripheral surface at the end of this outer peripheral surface that is located on the opposite side from the surface 11a in the thickness direction 11c.

[0054] If the cutting blade thickness of the cutting blade 18 is sufficiently large compared to the width of the stepped portion 11e, the stepped portion 11e can be formed, for example, by rotating the chuck table 4 once.

[0055] In contrast, if the cutting blade thickness of the cutting blade 18 is smaller than the width of the stepped portion 11e, the rotation of the chuck table 4 is continued, and the cutting blade 18 repeatedly cuts into the wafer 11 in the X-axis direction, pulls out the cutting blade 18 from the wafer 11 in the X-axis direction, and adjusts the position of the cutting blade 18 relative to the wafer 11 in the Y-axis direction.

[0056] In the first cutting process S10, concentric cutting marks are formed on the bottom 11e1 of the stepped portion 11e due to the rotation of the chuck table 4 (see Figures 6(B) and 6(C)). The concentric cutting marks create irregularities on the bottom 11e1 (see Figure 6(B)).

[0057] The irregularities on the bottom portion 11e1 are formed, for example, due to the fact that the amount of abrasive grains protruding from the bonding material of the cutting blade 18 (i.e., the protruding length) varies in the thickness direction of the cutting blade 18.

[0058] In this embodiment, after the first cutting step S10, the bottom portion 11e1 of the stepped portion 11e is cut by moving the chuck table 4 and the cutting unit 12 (i.e., the spindle 16) relative to each other (second cutting step S20).

[0059] Figure 4(A) is a partial cross-sectional side view showing the start of the second cutting process S20, and Figure 4(B) is a top view showing the start of the second cutting process S20.

[0060] The second cutting step S20 includes moving the chuck table 4 and the cutting blade 18 relative to each other along the Y-axis while maintaining the height position of the cutting unit 12 (i.e., the spindle 16) relative to the chuck table 4.

[0061] In the second cutting step S20 of this embodiment, while maintaining the rotation of the spindle 16 and keeping the chuck table 4 stationary within the cutting apparatus 2 without rotating it, the cutting unit 12 (i.e., the spindle 16, cutting blade 18, etc.) is moved along the Y axis to the radially outward side of the holding surface 4a (i.e., in the -Y direction) at a predetermined speed of 1 mm / s to 50 mm / s.

[0062] In the second cutting process S20, similar to the spark-out in the grinding process of the wafer 11 using a grinding wheel, the cutting feed rate of the cutting blade 18 in the Z-axis direction is set to zero (i.e., the height position of the cutting blade 18 is maintained), and the cutting blade 18, which is rotating around the spindle 16, is moved radially outward from the holding surface 4a along the Y-axis.

[0063] In this manner, the chuck table 4 and the cutting blade 18 are moved relative to each other along the Y-axis until the lower end of the cutting blade 18 is completely separated from the wafer 11. Note that the direction of movement of the cutting blade 18 relative to the chuck table 4 is not limited to the Y-axis direction.

[0064] The cutting blade 18 may be moved along the X-axis relative to the chuck table 4 until its lower end is completely separated from the wafer 11. Alternatively, the cutting blade 18 may be moved along the Y-axis while simultaneously moving along the X-axis relative to the chuck table 4.

[0065] In short, the goal is to cut the bottom 11e1 of the stepped portion 11e by moving the rotating cutting blade 18 in parallel along the holding surface 4a in the XY plane while maintaining the height position of the cutting blade 18.

[0066] Figure 5(A) is a partial cross-sectional side view showing the end of the second cutting process S20, and Figure 5(B) is a top view showing the end of the second cutting process S20. Figure 6(A) is a top view of the wafer 11 after the second cutting process S20.

[0067] Figure 6(B) is a schematic cross-sectional view of Figure 6(A) at point AA before cutting in the second cutting process S20, and Figure 6(C) is a schematic cross-sectional view of Figure 6(A) at point BB after cutting in the second cutting process S20.

[0068] Figures 6(B) and 6(C) are illustrative examples of possible configurations of the bottom 11e1 of the stepped portion 11e, and the shape of the bottom 11e1 of the stepped portion 11e is not limited to those shown in Figures 6(B) and 6(C).

[0069] In the surface reduction region 11e2 where the second cutting process S20 is performed, as the cutting blade 18 is moved relative to the wafer 11 while rotating the cutting blade 18, new cutting marks with a diagonal pattern are formed when viewed from above (see Figures 5(B) and 6(A)).

[0070] However, in the unevenness reduction region 11e2, the unevenness is reduced compared to the unevenness non-reduction region 11e3, where the second cutting process S20 has not been performed on the bottom portion 11e1 (see Figure 6(C)). In other words, the second cutting process S20 can reduce the unevenness formed on the bottom portion 11e1 of the stepped portion 11e in the first cutting process S10.

[0071] After the second cutting process S20, the measurement process S30 is performed. Figure 7 is a partial cross-sectional side view showing the measurement process S30. In the measurement process S30, measurement light L is irradiated from the sensor head 22 onto the bottom 11e1 (i.e., the unevenness reduction region 11e2) of the stepped portion 11e that has been subjected to the second cutting process S20, and the distance L1 from the back surface 11b of the wafer 11 to the bottom 11e1 of the stepped portion 11e is measured.

[0072] By first measuring the distance L2 (not shown) from the sensor head 22 to the holding surface 4a, and then measuring the distance L3 (not shown) from the sensor head 22 to the bottom 11e1 of the stepped portion 11e, the above-mentioned distance L1 (see Figure 7), which is the difference between distance L2 and distance L3, is obtained. Distance L1 is the remaining thickness of the wafer 11 formed on the outer periphery of the wafer 11 by forming the stepped portion 11e.

[0073] In this embodiment, as a result of reducing the unevenness of the bottom 11e1 of the stepped portion 11e, the measurement light L irradiated onto the unevenness reduction region 11e2 is more easily reflected appropriately by the bottom 11e1 of the stepped portion 11e. Therefore, the remaining thickness of the wafer 11 at the outer edge can be measured more accurately compared to when the measurement light L is irradiated onto the non-unreduced unevenness region 11e3.

[0074] (Second Embodiment) Next, a second embodiment will be described with reference to Figures 8(A) to 9(B). Figure 8(A) is a partial cross-sectional side view showing the start of the second cutting process S20 according to the second embodiment, and Figure 8(B) is a top view showing the start of the second cutting process S20 according to the second embodiment.

[0075] In the second cutting step S20 of the second embodiment, the rotation of the spindle 16 is maintained, and the cutting blade 18 is moved radially outward from the holding surface 4a along the Y axis while the chuck table 4 is rotated. This point differs from the first embodiment.

[0076] Figure 9(A) is a top view showing a first example of the wafer 11 after the second cutting process S20 according to the second embodiment. Figure 9(A) shows an example in which a spiral cutting mark is formed on the stepped portion 11e due to the rotation speed of the chuck table 4 being greater than the speed of movement of the cutting blade 18 in the Y-axis direction.

[0077] In the first example as well, the irregularities formed on the bottom 11e1 of the stepped portion 11e can be reduced. Furthermore, in Figure 9(A), since the irregularity reduction region 11e2 exists over almost the entire bottom 11e1 of the stepped portion 11e, there is the advantage that thickness measurement using the measuring light L is possible anywhere on the bottom 11e1.

[0078] Figure 9(B) is a top view showing a second example of the wafer 11 after the second cutting process S20 according to the second embodiment. Figure 9(B) shows an example in which the surface irregularity reduction region 11e2 is approximately a parallelogram, rather than a rectangle as shown in Figure 6(A), due to the fact that the speed of movement of the cutting blade 18 in the Y-axis direction is greater than the speed of rotation of the chuck table 4.

[0079] In the second example as well, the irregularities formed on the bottom 11e1 of the stepped portion 11e can be reduced. Furthermore, although the range of the irregularity reduction region 11e2 in Figure 9(B) is narrower than the range of the irregularity reduction region 11e2 in Figure 9(A), it has the advantage that the second cutting process S20 can be completed in a shorter time compared to the second cutting process S20 in Figure 9(A).

[0080] (Third Embodiment) Next, the third embodiment will be described with reference to Figures 10 to 11(B). Figure 10 is a flowchart of the wafer cutting method in the third embodiment. In the third embodiment, if the second cutting process S20 is not repeated after the second cutting process S20 (NO in the determination process S22), the flow is terminated after the measurement process S30 described above.

[0081] In contrast, if the second cutting process S20 is repeated after the second cutting process S20 (YES in the decision process S22), the process proceeds to the chuck table rotation process S24, in which the chuck table 4 is rotated by a predetermined angle. The rotation angle is not particularly limited, but for example, it is in the range of 5° to 180°. After the chuck table rotation process S24, the process proceeds to the third cutting process S26.

[0082] In the third cutting step S26, while maintaining the height position of the spindle 16 relative to the chuck table 4, the cutting blade 18 is moved relative to the chuck table 4 in the opposite direction (for example, the +Y direction) to the direction of movement of the cutting blade 18 relative to the chuck table 4 in the second cutting step S20 (for example, the -Y direction).

[0083] In the third cutting step S26, as in the second cutting step S20, the irregularities formed on the bottom 11e1 of the stepped portion 11e can be reduced. At the end of the third cutting step S26, the relative position of the cutting blade 18 in the radial direction of the chuck table 4 is the same as the relative position of the cutting blade 18 in the radial direction of the chuck table 4 at the end of the second cutting step S20.

[0084] Then, after the third cutting process S26, the process returns to the second cutting process S20. After the second cutting process S20, if the decision in the judgment process S22 is again YES, the process proceeds to the third cutting process S26. In this manner, in this embodiment, the second cutting process S20, the chuck table rotation process S24 after the second cutting process S20, and the third cutting process S26 after the chuck table rotation process S24 are repeated multiple times in this order.

[0085] Figure 11(A) is a top view showing a first example of a wafer 11 cut by the cutting method of the third embodiment. In the first example, in the second cutting step S20 and the third cutting step S26, a surface irregularity reduction region 11e2 is formed at the bottom 11e1 of the stepped portion 11e.

[0086] Therefore, by repeating the second cutting process S20, the chuck table rotation process S24, and the third cutting process S26, a plurality of surface irregularity reduction regions 11e2 are formed at approximately equal intervals along the circumferential direction of the wafer 11.

[0087] Figure 11(B) is a top view showing a second example of a wafer 11 cut by the cutting method of the third embodiment. In the second example, similar to Figure 9(B) of the second embodiment, the chuck table 4 is rotated in both the second cutting step S20 and the third cutting step S26.

[0088] In addition, in the second cutting step S20, the cutting blade 18 is moved from the inside to the outside in the radial direction of the holding surface 4a, and in the third cutting step S26, the cutting blade 18 is moved from the outside to the inside in the radial direction of the holding surface 4a. Therefore, the shape of the unevenness reduction region 11e2 is different in the second cutting step S20 and the third cutting step S26.

[0089] (Fourth Embodiment) Next, the fourth embodiment will be described with reference to Figures 12 to 13(B). Figure 12 is a flowchart of the wafer cutting method in the fourth embodiment. Figure 13(A) is a top view showing a first example of a wafer 11 cut by the cutting method of the fourth embodiment.

[0090] In the first example of the fourth embodiment, if the second cutting process S20 is repeated after the second cutting process S20 (YES in the decision process S22), the process proceeds to the third cutting process S26 without going through the chuck table rotation process S24 in the third embodiment.

[0091] However, in the second cutting process S20, the chuck table 4 is rotated (i.e., while the rotation continues) and the chuck table 4 and the cutting blade 18 are moved relative to each other. This moves the cutting blade 18 away from the stepped portion 11e.

[0092] In this second cutting process S20, the spiral-shaped unevenness reduction region 11e shown in Figure 13(A) 2A A stump is formed at the bottom 11e1. Once the cutting blade 18 has completely separated from the wafer 11 (i.e., when the second cutting process S20 is completed), the rotation of the chuck table 4 is stopped.

[0093] Then, with the rotation of the chuck table 4 stopped, the third cutting process S26 is performed. In the third cutting process S26, the roughly rectangular unevenness reduction region 11e shown in Figure 13(A) is cut. 2B A bottom portion 11e1 is formed.

[0094] By repeating the second cutting process S20 and the third cutting process S26 multiple times, a surface area 11e is created in the bottom portion 11e1. 2A and unevenness reduction area 11e 2B These are formed periodically. Of course, the rotation of the cutting blade 18 (i.e., the spindle 16) is continued during each cutting process.

[0095] Figure 13(B) is a top view showing a second example of a wafer 11 cut by the cutting method of the fourth embodiment. In the second example of the fourth embodiment, the second cutting step S20 and the third cutting step S26 are repeated while the chuck table 4 is rotated (i.e., while the rotation is continuous).

[0096] However, in the second cutting process S20, the speed of movement of the cutting blade 18 is relatively small relative to the rotation speed of the chuck table 4, while in the third cutting process S26, the speed of movement of the cutting blade 18 is relatively large relative to the rotation speed of the chuck table 4.

[0097] Therefore, in the second cutting process S20, the spiral-shaped unevenness reduction region 11e 2A Although a roughly parallelogram-shaped unevenness reduction region 11e is formed at the bottom 11e1, in the third cutting step S26, a roughly parallelogram-shaped unevenness reduction region 11e is formed similar to that in Figure 9(B) of the second embodiment. 2B A bottom portion 11e1 is formed.

[0098] (Fifth Embodiment) Next, the fifth embodiment will be described with reference to Figures 14 to 19(C). Figure 14 is a flowchart of the cutting method for the bonded wafer 21 (see Figures 15(A) and 15(B)) in the fifth embodiment.

[0099] First, let's describe the bonded wafer (i.e., the workpiece) 21. Figure 15(A) is a side view of the bonded wafer 21, and Figure 15(B) is a top view of the bonded wafer 21.

[0100] The bonded wafer 21 has a lower wafer 15 and an upper wafer 17 fixed to each other via a bonding layer (not shown), and is also called a laminated wafer. The shapes of the lower wafer 15 and the upper wafer 17 are substantially the same as those of the wafer 11 described above.

[0101] The lower wafer 15 has a front surface (i.e., the other side) 15a and a back surface (i.e., one side) 15b. The front surface 15a and the back surface 15b are located on opposite sides in the thickness direction 15c of the lower wafer 15.

[0102] Multiple division lines (not shown) are arranged in a grid pattern on the surface 15a of the lower wafer 15, and devices such as ICs (not shown) are formed in each rectangular region demarcated by the multiple division lines.

[0103] Note that the lower wafer 15 does not necessarily have to have a device on it. The lower wafer 15 may be a substrate made of semiconductor, resin, metal, ceramics, glass, etc., which has approximately the same diameter as the upper wafer 17 and does not have a device.

[0104] The surface 15a of the lower wafer 15 has a chamfered portion 15a1 on its outer periphery, and similarly, the back surface 15b also has a chamfered portion 15b1 on its outer periphery. In the thickness direction 15c, an edge 15d that defines the outermost periphery of the lower wafer 15 exists between the chamfered portion 15a1 of the surface 15a and the chamfered portion 15b1 of the back surface 15b.

[0105] The shape of the lower wafer 15 is not limited to the shape shown in Figure 15(A). The lower wafer 15 does not have a chamfered portion 15a1 on the outer periphery of the surface 15a and a chamfered portion 15b1 on the outer periphery of the back surface 15b, and the intersection regions of the outer periphery side surface of the lower wafer 15 and the surface 15a and back surface 15b may be angular.

[0106] The upper wafer 17 also has a front surface 17a and a back surface 17b located on opposite sides in the thickness direction 17c. The front surface 17a of the upper wafer 17 is divided by a plurality of division lines, and a device (not shown) is formed in each rectangular region divided by the plurality of division lines.

[0107] The surface 17a of the upper wafer 17 has a chamfered portion 17a1 on its outer edge, and similarly, the back surface 17b also has a chamfered portion 17b1 on its outer edge. In the thickness direction 17c, an edge 17d that defines the outermost edge of the upper wafer 17 exists between the chamfered portion 17a1 of the surface 17a and the chamfered portion 17b1 of the back surface 17b.

[0108] In this embodiment, the cutting apparatus 2 described above is used to perform the first cutting process S10 to the imaging process S60 shown in Figure 14. The first cutting process S10 in this embodiment is substantially the same as the first cutting process S10 in the first embodiment, so redundant explanations may be omitted.

[0109] Figure 16(A) is a partial cross-sectional side view showing the first cutting process S10. In the first cutting process S10 of this embodiment, a cutting blade 18A with a relatively large average particle size of abrasive grains (a so-called coarse blade) is used.

[0110] In the first cutting process S10, the cutting blade 18A cuts into the outer periphery of the upper wafer 17 such that the thickness from the bottom 11e1 to the surface 17a of the stepped portion 11e in the thickness direction 15c, 17c (i.e., the remaining thickness 17e of the stepped portion 11e) is a predetermined value of 10 μm or more and 50 μm or less.

[0111] After cutting the outer periphery of the upper wafer 17 with the cutting blade 18A in this manner, the chuck table 4 is rotated to form a stepped portion 11e on the outer periphery of the back surface 17b of the upper wafer 17, similar to the first embodiment. After the first cutting process S10, the second cutting process S20 is performed, similar to the first embodiment.

[0112] Figure 16(B) is a partial cross-sectional side view showing the second cutting process S20. The second cutting process S20 in this embodiment is substantially the same as the second cutting process S20 in the first embodiment, so redundant explanations may be omitted.

[0113] In the second cutting process S20, while maintaining the rotation of the spindle 16 and keeping the chuck table 4 stationary within the cutting apparatus 2 without rotating it, the cutting unit 12 is moved radially outward from the holding surface 4a along the Y axis.

[0114] This process cuts the bottom portion 11e1 of the stepped portion 11e of the upper wafer 17, forming a surface irregularity reduction region 11e2 on the bottom portion 11e1. After the second cutting process S20, the measurement process S30 is performed. Figure 17 is a partial cross-sectional side view showing the measurement process S30.

[0115] In the measurement step S30, the measurement light L is irradiated onto the unevenness reduction region 11e2 formed by the second cutting step S20. This allows for more accurate measurement of the remaining thickness 17e at the outer edge of the upper wafer 17 compared to when the measurement light L is irradiated onto the non-unevenness reduction region 11e3. Therefore, the cutting depth position of the cutting blade 18B in the subsequent additional first cutting step S40 can be controlled with high precision.

[0116] After the measurement process S30, an additional first cutting process S40 is performed. Figure 18(A) is a partial cross-sectional side view showing the additional first cutting process S40. In the additional first cutting process S10, a cutting blade (so-called finishing blade) 18B is used, in which the average particle size of the abrasive grains is smaller than that of the cutting blade 18A.

[0117] In the additional first cutting step S40, similar to the first cutting step S10, the cutting blade 18B is driven into the bottom 11e1 of the stepped portion 11e of the upper wafer 17, and the chuck table 4 is rotated. Specifically, the lower end of the cutting blade 18 is positioned about 1 μm to 2 μm deeper than the surface 15a of the lower wafer 15, and the chuck table 4 is rotated.

[0118] This further deepens the stepped portion 11e and forms a stepped portion 21a, which is composed of the cylindrical outer peripheral side surface of the upper wafer 17 and the cylindrical outer peripheral side surface located near the surface 15a of the lower wafer 15, and the annular outer peripheral portion of the lower wafer 15 that is exposed and not covered by the upper wafer 17 (i.e., the bottom portion 21a1, which will be described later).

[0119] After the additional first cutting step S40, an additional second cutting step S50 is performed. Figure 18(B) is a partial cross-sectional side view showing the additional second cutting step S50. The cutting blade 18B is also used in the additional second cutting step S50.

[0120] In the additional second cutting step S50, similar to the second cutting step S20, the outer periphery of the lower wafer 15 constituting the stepped portion 21a is cut by relatively moving the chuck table 4 and the cutting blade 18. This forms a surface roughness reduction region 21a2 at the bottom 21a1 of the stepped portion 21a. The bottom 21a1 other than the surface roughness reduction region 21a2 becomes a surface roughness non-reduction region 21a3.

[0121] After the additional second cutting step S50, the imaging step S60 is performed. Figure 19(A) is a partial cross-sectional side view showing the imaging step S60. In the imaging step S60, for example, a microscope camera 30 that images the object with visible light is used.

[0122] The microscope camera 30 includes a light source, an objective lens, an imaging lens, a solid-state image sensor, etc. (none of which are shown). In imaging step S60, a lens unit 32 equipped with an objective lens is placed above the stepped portion 21a, and the bottom portion 21a1 of the stepped portion 21a (i.e., the unevenness reduction region 21a2) which has undergone the additional second cutting step S50 is imaged.

[0123] An identification number is provided on the outer periphery of the surface 15a of the lower wafer 15. Since the ID number is formed to a certain depth from the surface 15a by laser engraving or the like, the ID number remains on the outer periphery of the surface 15a even after the additional second cutting process S20.

[0124] In imaging step S60, the unevenness reduction region 11e2 formed by the additional second cutting step S50 is imaged, which has the advantage of allowing for clearer imaging of the ID numbers remaining on the outer periphery of the lower wafer 15.

[0125] Figure 19(B) is a schematic diagram of an image obtained in imaging step S60 of the fifth embodiment. In contrast, Figure 19(C) is a schematic diagram of an image obtained in a conventional imaging step that images the outer periphery of the lower wafer 15, which has not undergone the additional second cutting step S50.

[0126] Although a detailed explanation will be omitted, in the fifth embodiment as well, the second embodiment may be applied in the second cutting step S20, and the third or fourth embodiment, which performs the third cutting step S26, may be applied from the second cutting step S20 to the measurement step S30.

[0127] Similarly, the second embodiment may be applied to the additional second cutting step S50, and similarly, the third or fourth embodiment, which performs the third cutting step S26, may be applied from the additional second cutting step S50 to the imaging step S60.

[0128] Furthermore, the structures, methods, etc., according to the above embodiments can be modified as appropriate without departing from the scope of the object of the present invention. The bottom portions 11e1 and 21a1 of the stepped portions 11e and 21a may be read as bottom surfaces. [Explanation of Symbols]

[0129] 2:Cutting device 4: Chuck table, 4a: Holding surface, 6: Frame, 6a: Recess, 8: Porous plate 10: axis of rotation, 10a: center of rotation 11: Wafer (workpiece) 11a: Surface (one side), 11a1: Chamfered part 11b: Back surface, 11b1: Chamfered area 11c: thickness direction, 11d: edge, 11e: stepped portion, 11e1: bottom 11e2,11e 2A ,11e2B : Area with reduced unevenness, 11e3: Area without reduced unevenness 12: Cutting unit, 14: Spindle housing 15: Lower wafer 15a: Surface, 15a1: Chamfered part 15b: Reverse side (one side), 15b1: Chamfered part 15c: thickness direction, 15d: edge 16: Spindle, 16a: Center of rotation 17: Upper wafer 17a: Surface, 17a1: Chamfered portion 17b: Reverse side, 17b1: Chamfered part 17c: thickness direction, 17d: edge, 17e: remaining thickness 18, 18A, 18B: Cutting blades 20: Thickness measuring instrument, 22: Sensor head 21: Bonded wafer (workpiece) 21a: Step part, 21a1: Bottom part, 21a2: Unevenness reduction area, 21a3: Unevenness reduction area 30: Microscope camera, 32: Lens unit L: Measuring light, L1, L2, L3: Distance S10: 1st cutting process, S20: 2nd cutting process S22: Decision-making process, S24: Chuck table rotation process S26: 3rd cutting process, S30: Measuring process S40: Additional first cutting process, S50: Additional second cutting process, S60: Imaging process

Claims

1. A cutting method for a workpiece having a chamfered portion on the outer circumference of one surface, wherein the chamfered portion on that surface is removed and an annular stepped portion is formed on the outer circumference of that surface, A first cutting step involves cutting the outer circumference of one surface of the workpiece, which is held on the holding surface of the chuck table, into the chamfered portion of that surface, with a cutting blade attached to the tip of a spindle whose longitudinal direction is aligned with the holding surface, and rotating the chuck table to cut the outer circumference of that surface of the workpiece and form the stepped portion. A second cutting step is performed in which the bottom of the stepped portion is cut by moving the chuck table and the cutting blade relative to each other after the first cutting step, Equipped with, A method for cutting a workpiece, characterized in that the second cutting step includes moving the chuck table and the cutting blade relative to each other along the longitudinal direction of the spindle while maintaining the height position of the spindle relative to the chuck table.

2. The method for cutting a workpiece according to claim 1, characterized in that, in the second cutting step, the chuck table is rotated while the chuck table and the cutting blade are moved relative to each other.

3. The invention further comprises a third cutting step in which, while maintaining the height position of the spindle relative to the chuck table, the cutting blade is moved relative to the chuck table in a direction opposite to the direction of movement of the cutting blade relative to the chuck table in the second cutting step, The method for cutting a workpiece according to claim 2, characterized in that the second cutting step and the third cutting step are repeated multiple times.

4. After the second cutting step, a chuck table rotation step is performed in which the chuck table is rotated by a predetermined angle, A third cutting step is performed in which, after the chuck table rotation step, the cutting blade is moved relative to the chuck table in the opposite direction to the direction of movement of the cutting blade relative to the chuck table in the second cutting step, while maintaining the height position of the spindle relative to the chuck table. The method for cutting a workpiece according to claim 1, further comprising the above.

5. The second cutting process and, The chuck table rotation step after the second cutting step, The third cutting step after the chuck table rotation step, The method for cutting a workpiece according to claim 4, characterized in that the steps are repeated in this order.

6. The workpiece comprises a lower wafer and an upper wafer having chamfered edges on both sides and being fixed on top of the lower wafer. In the first cutting process, the stepped portion is formed on the outer periphery of the upper wafer. The method for cutting a workpiece according to claim 1, characterized in that the second cutting step involves cutting the bottom of the stepped portion of the upper wafer.

7. A method for cutting a workpiece according to any one of claims 1 to 6, further comprising a measurement step of irradiating the bottom of the stepped portion that has been subjected to the second cutting step with measuring light from a sensor head, and measuring the distance from the other surface of the workpiece located opposite to the one surface to the bottom of the stepped portion.

8. After the second cutting step, the cutting blade is driven into the bottom of the stepped portion and the chuck table is rotated to deepen the stepped portion, and an additional first cutting step is performed to form the stepped portion with the outer peripheral side surface of the upper wafer, the outer peripheral side surface of the lower wafer, and the outer peripheral portion of the lower wafer. After the additional first cutting step, an additional second cutting step is performed to cut the outer periphery of the lower wafer that constitutes the stepped portion, The method for cutting a workpiece according to claim 6, further comprising the above.

9. The method for cutting a workpiece according to claim 8, further comprising an imaging step of imaging the bottom of the stepped portion that has been subjected to the additional second cutting step.

Images