Peeling method, method for manufacturing a wafer, and peeling apparatus

Abstract

To provide a peeling method and a peeling device, capable of peeling a wafer after an ingot in which a peeling layer is formed is separated in the peeling layer even when the ingot becomes thin.SOLUTION: In a state where an outer peripheral region of a lower surface of an ingot is sucked and a lower side of a circumference of an arc-like part of an outer periphery of the lower surface of the ingot is released, a supersonic wave is applied to an upper surface of the ingot via a liquid layer. In such a case, since the lower side of the circumference of the arc-like part of the outer periphery of the lower surface of the ingot is opened, liquid which becomes a medium of the supersonic wave is not accumulated in the circumference of the arc-like part of the outer periphery of the lower surface of the ingot. Thus, a peeling layer formed inside the ingot is not immersed in the liquid when applying the supersonic wave to the upper surface of the ingot via a layer of the liquid. As a result, a wafer can be peeled from the ingot by separating the ingot in the peeling layer even if the ingot becomes thin.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a peeling method and a peeling apparatus for peeling a cylindrical ingot having a peeling layer formed therein at the peeling layer to peel a disk-shaped wafer from the ingot.

Background Art

[0002] Chips of semiconductor devices are generally manufactured using disk-shaped wafers. Such wafers are produced, for example, by cutting a cylindrical semiconductor ingot (hereinafter also simply referred to as an ingot) using a wire saw and then polishing the surface (see, for example, Patent Document 1).

[0003] Specifically, when a wafer is cut from an ingot using a wire saw, fine irregularities are formed on the surface, and the wafer is curved as a whole (the wafer warps). Therefore, the wafer cut out in this way is often polished on the surface in order to remove the irregularities and flatten it.

[0004] However, when the wafer is polished, a part of the wafer becomes polishing dust and is discarded, and the wafer becomes thinner. Taking this point into consideration, when cutting a wafer from an ingot, the wafer is generally cut from the ingot to be thicker than the wafer used for manufacturing chips of semiconductor devices.

[0005] Ingots used for manufacturing chips of semiconductor devices are expensive. Therefore, when generating a wafer by a method that requires polishing, the manufacturing cost of chips of semiconductor devices manufactured using this wafer tends to be high.

[0006] Furthermore, single-crystalline SiC (silicon carbide), which is expected as a material for power devices, has a high hardness. Therefore, when cutting a wafer from a single-crystalline SiC ingot using a wire saw, the required time tends to be long, and the wire saw tends to wear out.

[0007] As a result, the manufacturing cost of single-crystal SiC wafers tends to be high. In view of this, a method has been proposed to peel wafers from an ingot using a laser beam and ultrasonic waves without using a wire saw (see, for example, Patent Document 2).

[0008] In this method, first, the ingot is irradiated with a laser beam while the focal point of the laser beam having a wavelength that penetrates the ingot is positioned at a predetermined depth from the upper surface of the ingot. As a result, a peeling layer with low strength (for example, a modified portion where SiC is separated into Si (silicon) and C (carbon) and a layer including cracks extending from the modified portion) is formed inside the ingot.

[0009] Next, ultrasonic waves are applied to the upper surface of the ingot through a liquid layer. As a result, new cracks are formed in the peeling layer, and existing cracks further extend, further reducing the strength of the peeling layer. Then, the upper surface side of the ingot is suctioned and pulled upward. As a result, the ingot is separated at the peeling layer and the wafer is peeled from the ingot.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] When a large number of wafers are peeled from an ingot, the ingot becomes thin. When using such a thin ingot, wafer peeling may become difficult compared to when using a sufficiently thick ingot.

[0012] In view of this point, an object of the present invention is to provide a peeling method and a peeling apparatus capable of separating an ingot having a peeling layer formed therein at the peeling layer and peeling a wafer from the ingot even when the ingot becomes thin.

Means for Solving the Problems

[0013] According to one aspect of the present invention, there is provided a peeling method for separating a columnar ingot having a peeling layer formed therein at the peeling layer and peeling a disk-shaped wafer from the ingot, wherein an outer peripheral region of a lower surface of the ingot is sucked, and a lower portion around an arc-shaped portion of the outer periphery of the lower surface of the ingot is open, As a result, the liquid flowing down along the side surface of the ingot from above around the portion does not stay around the portion but flows downwards. and a step of applying ultrasonic waves to an upper surface of the ingot through a liquid layer is included. Alternatively, according to one aspect of the present invention, there is provided a peeling method for peeling a disk-shaped wafer from a columnar ingot having a peeling layer formed therein by separating the ingot at the peeling layer, the method including an ultrasonic application step of applying ultrasonic waves to the upper surface of the ingot through a liquid layer in a state where the outer peripheral region of the lower surface of the ingot is sucked and the lower side around the arcuate portion of the outer periphery of the lower surface of the ingot is open, the ultrasonic application step being carried out in a state where the ingot is held on the holding surface of a chuck table, and the radius of the holding surface being designed to be approximately equal to the radius of the ingot in plan view.

[0014] According to another aspect of the present invention, A method for manufacturing a wafer in which a columnar ingot having a release layer formed therein is separated at the release layer to produce a disk-shaped wafer from the ingot, wherein an outer peripheral region of the lower surface of the ingot is sucked, and a lower portion around an arc-shaped portion of the outer periphery of the lower surface of the ingot is opened, so that a liquid flowing down along the side surface of the ingot from above around the portion does not stay around the portion but flows downwards, and an ultrasonic application step of applying ultrasonic waves to the upper surface of the ingot through a liquid layer; and a separation step of separating the ingot at the release layer to peel the wafer from the ingot after the ultrasonic application step. Alternatively, according to another aspect of the present invention, there is provided a method for manufacturing a wafer in which a columnar ingot having a release layer formed therein is separated at the release layer to produce a disk-shaped wafer from the ingot, wherein an outer peripheral region of the lower surface of the ingot is sucked, and a lower portion around an arc-shaped portion of the outer periphery of the lower surface of the ingot is opened, and an ultrasonic application step of applying ultrasonic waves to the upper surface of the ingot through a liquid layer; and a separation step of separating the ingot at the release layer to peel the wafer from the ingot after the ultrasonic application step, wherein the ultrasonic application step is carried out with the ingot held on a holding surface of a chuck table, and the radius of the holding surface is designed to be approximately equal to the radius of the ingot in plan view.

[0015] According to still another aspect of the present invention, there is provided a peeling device for separating a columnar ingot having a peeling layer at the peeling layer to peel a disk-shaped wafer from the ingot, the peeling device comprising: an ultrasonic application unit for applying ultrasonic waves to the upper surface of the ingot through a liquid layer; and a chuck table having a circular holding surface for sucking and holding the outer peripheral region of the lower surface of the ingot, the holding surface having a flat circular central region, an annular suction region surrounding the central region and communicating with a suction source through a suction passage, and a flat annular outermost region surrounding the suction region and located at the outermost side of the holding surface, the width along the radial direction of the holding surface of the outermost region surrounding the arcuate portion of the outer periphery of the suction region being 5% or less of the radius of the holding surface, and the distance between the arcuate portion of the outer periphery of the central region and the center of the holding surface being 70% or more of the radius of the holding surface. Alternatively, according to still another aspect of the present invention, there is provided a peeling device for separating a columnar ingot having a peeling layer at the peeling layer to peel a disk-shaped wafer from the ingot, the peeling device comprising: an ultrasonic application unit for applying ultrasonic waves to the upper surface of the ingot through a liquid layer; and a chuck table having a circular holding surface for sucking and holding the outer peripheral region of the lower surface of the ingot, the holding surface having a flat circular central region, an annular suction region surrounding the central region and communicating with a suction source through a suction passage, and a flat annular outermost region surrounding the suction region and located at the outermost side of the holding surface, the width along the radial direction of the holding surface of the outermost region surrounding the arcuate portion of the outer periphery of the suction region being 5% or less of the radius of the holding surface, and the liquid flowing down along the side surface of the ingot from above the periphery of the portion without being blocked by the outermost region below the periphery of the arcuate portion of the outer periphery of the lower surface of the ingot, and ultrasonic waves being applied to the upper surface of the ingot through a liquid layer in a state where the liquid flows down without staying around the periphery of the portion.

[0016] Furthermore, in the peeling device of the present invention, it is preferable that the upper part of the chuck table including the holding surface is made of stainless steel. Further, in the peeling apparatus of the present invention, the ultrasonic wave applying unit preferably includes a first ultrasonic wave applying unit that applies ultrasonic waves to a first region of the upper surface of the ingot with a first energy density, and a second ultrasonic wave applying unit that applies ultrasonic waves to a second region wider than the first region of the upper surface of the ingot with a second energy density lower than the first energy density.

Effects of the Invention

[0017] In the present invention, even when the ingot becomes thin, the ingot can be separated at the peeling layer and the wafer can be peeled from the ingot.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

[0019] When the inventors of the present invention were earnestly verifying the fact that when peeling a wafer from an ingot, if the ingot is thin, it becomes difficult to peel the wafer, they found that the peeling of the wafer from the ingot becomes difficult because the peeling layer formed inside the ingot is immersed in a liquid.

[0020] Specifically, the application of ultrasonic waves to the upper surface of the ingot is performed while the lower surface of the ingot is sucked and held by a chuck table having a holding surface with a size wider than that of the lower surface of the ingot. Then, when ultrasonic waves are applied to the upper surface of the ingot through a liquid layer in this state, this liquid flows along the side surface of the ingot and accumulates on the holding surface of the chuck table.

[0021] Here, as the ingot held by the chuck table becomes thinner, the distance between the peeling layer formed inside the ingot and the holding surface of the chuck table becomes shorter. Therefore, if the ingot becomes thinner, the probability that the peeling layer is immersed in the liquid accumulated on the holding surface of the chuck table when ultrasonic waves are applied to the upper surface of the ingot becomes higher.

[0022] Therefore, the inventors of the present invention applied a chuck table having a holding surface with a size sufficiently smaller than the lower surface of the ingot as a chuck table that sucks and holds the lower surface of the ingot when applying ultrasonic waves to the upper surface of the ingot, and tried to peel the wafer from the ingot. However, even in this case, it was sometimes difficult to peel the wafer from the ingot.

[0023] The inventors of the present invention also earnestly verified this point and found that the peeling of the wafer from the ingot becomes difficult because the outer peripheral region of the lower surface of the ingot is not sucked. That is, the inventors of the present invention found that when the outer peripheral region of the lower surface of the ingot is not sucked, ultrasonic waves are not efficiently propagated to the region of the peeling layer located directly above this outer peripheral region, and the extension of cracks in this region of the peeling layer is inhibited.

[0024] Based on the above findings, the inventors have completed the present invention. Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1(A) is a perspective view schematically showing an example of an ingot, and FIG. 1(B) is a side view schematically showing an example of the ingot. The ingot 11 shown in FIGS. 1(A) and 1(B) is a columnar single-crystal SiC ingot having generally parallel upper surface 11a and lower surface 11b.

[0025] The ingot 11 is manufactured using epitaxial growth. And, in order to reduce lattice defects formed inside the ingot 11, the c-axis 11c of single-crystal SiC is generated so as to be slightly inclined with respect to the perpendicular line 11d of the upper surface 11a and the lower surface 11b. For example, the angle (off-angle) α formed between the c-axis 11c and the perpendicular line 11d is 1° to 6° (typically, 4°).

[0026] On the side surface of the ingot 11, a flat portion indicating the crystal orientation of single-crystal SiC, that is, an orientation flat 13 is formed. And this orientation flat 13 is formed so as to be parallel to the intersection line where the plane parallel to the c-plane 11e of single-crystal SiC intersects the upper surface 11a or the lower surface 11b.

[0027] Note that the ingot 11 may be made of a semiconductor material other than SiC (for example, silicon (Si) or gallium nitride (GaN), etc.). Also, an orientation flat 13 may not be formed on the side surface of the ingot 11. Alternatively, another orientation flat may be formed on the side surface of the ingot 11 in addition to the orientation flat 13, or a notch indicating the crystal orientation of the material constituting the ingot may be formed instead of the orientation flat 13.

[0028] FIG. 2 is a flowchart showing an example of a peeling method for peeling a wafer from an ingot. In this method, first, a laser beam is irradiated onto the ingot 11 to form a peeling layer (peeling layer formation step: S1).

[0029] FIG. 3 is a perspective view schematically showing the state of the peeling layer formation step (S1). Specifically, FIG. 3 is a perspective view schematically showing the state of irradiating the ingot 11 with a laser beam from the upper surface 11a side in the laser irradiation apparatus. Note that the X1-axis direction and the Y1-axis direction shown in FIG. 3 are directions orthogonal to each other on the horizontal plane, and the Z1-axis direction is a direction (vertical direction) orthogonal to the X1-axis direction and the Y1-axis direction.

[0030] The laser irradiation apparatus 2 shown in FIG. 3 has a circular holding surface substantially parallel to the horizontal plane, and has a chuck table 4 capable of holding the ingot 11 on this holding surface. This chuck table 4 is connected to a suction source (not shown).

[0031] This suction source has an ejector or the like and can generate a negative pressure in the space near the holding surface of the chuck table 4. When the suction source operates with the ingot 11 placed on the holding surface, the ingot 11 is sucked and held by the chuck table 4.

[0032] Furthermore, the chuck table 4 is connected to an X1-axis direction moving mechanism (not shown) and a Y1-axis direction moving mechanism (not shown). Each of the X1-axis direction moving mechanism and the Y1-axis direction moving mechanism has, for example, a ball screw and a motor or the like. When the X1-axis direction moving mechanism and / or the Y1-axis direction moving mechanism operates, the chuck table 4 moves along the X1-axis direction and / or the Y1-axis direction.

[0033] Also, the chuck table 4 is connected to a rotation mechanism (not shown). The rotation mechanism has, for example, a spindle and a motor or the like. When the rotation mechanism operates, the chuck table 4 rotates about a straight line along the Z1-axis direction passing through the center of the holding surface as the rotation axis.

[0034] Above the chuck table 4, a head 8 of a laser irradiation unit 6 is provided. The head 8 is provided at the tip (one end) of a connecting portion 10 extending along the Y1-axis direction. Note that the head 8 houses an optical system such as a condenser lens and a mirror, and the connecting portion 10 houses an optical system such as a mirror and / or a lens.

[0035] The other end of the connecting portion 10 is connected to a Z1-axis direction movement mechanism (not shown). The Z1-axis direction movement mechanism has, for example, a ball screw and a motor. When the Z1-axis direction movement mechanism operates, the head 8 and the connecting portion 10 move along the Z1-axis direction.

[0036] Further, the laser irradiation unit 6 has a laser oscillator (not shown) that generates a laser beam having a wavelength (for example, 1064 nm) that passes through the ingot 11. This laser oscillator has, for example, Nd:YAG as a laser medium. When a laser beam is generated by the laser oscillator, the laser beam is irradiated onto the holding surface side of the chuck table 4 through the optical systems housed in the connecting portion 10 and the head 8.

[0037] Furthermore, an imaging unit 12 capable of imaging the holding surface side of the chuck table 4 is provided on the side portion of the connecting portion 10. The imaging unit 12 has, for example, a light source such as an LED (Light Emitting Diode), an objective lens, and an imaging element such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The objective lens of the imaging unit 12 is provided at a position separated along the X1-axis direction as viewed from the head 8.

[0038] The peeling layer formation step (S1) is performed, for example, in the following order. First, the ingot 11 is placed on the holding surface of the chuck table 4 so that the upper surface 11a faces upward. Next, the suction source is operated so that the ingot 11 is sucked and held by the chuck table 4.

[0039] Next, based on an image of the upper surface 11a of the ingot 11 formed by imaging with the imaging unit 12, etc., the rotation mechanism rotates the chuck table 4 so that the orientation flat 13 becomes parallel to the X1-axis direction. Next, the X1-axis direction movement mechanism and / or the Y1-axis direction movement mechanism move the chuck table 4 so that the head 8 is positioned above the outside of the side surface of the ingot 11.

[0040] Next, the optical system of the head 8 and / or the connecting portion 10 is set so that the condensing point of the laser beam irradiated from the laser irradiation unit 6 is positioned at the height between the upper surface 11a and the lower surface 11b of the ingot 11. For example, the Z1-axis direction movement mechanism moves the head 8 and the connecting portion 10 so that the distance in the Z1-axis direction between the condensing lens housed in the head 8 and the upper surface 11a of the ingot 11 becomes a predetermined distance.

[0041] Note that such setting of the optical system may be performed at any timing as long as it is before the irradiation of the laser beam onto the ingot 11. For example, the setting of the optical system may be performed prior to the rotation and movement of the chuck table 4 described above. Also, such setting of the optical system is performed so that the distance between the condensing point of the laser beam and the upper surface 11a of the ingot 11 is slightly larger than the thickness of the wafer used for manufacturing the chips of the semiconductor device.

[0042] Next, while the X1-axis direction movement mechanism moves the chuck table 4 so that the condensing point of the laser beam is positioned inside the ingot 11, the laser irradiation unit 6 irradiates a laser beam having a wavelength that can penetrate the ingot 11. That is, the laser irradiation unit 6 irradiates the ingot 11 with a laser beam while relatively moving the ingot 11 and the condensing point of the laser beam along the intersection line where the plane parallel to the c-plane 11e of the ingot 11 (single crystal SiC) intersects the upper surface 11a.

[0043] Next, the irradiation with the same laser beam is repeated. Specifically, the same laser beam is irradiated onto a linear region along the X1-axis that is separated from a linear region along the X1-axis by a predetermined distance in the Y1-axis direction from the linear region along the X1-axis of the ingot 11 irradiated with the laser beam. As a result, in a cross-section parallel to the upper surface 11a and the lower surface 11b of the ingot 11, a plurality of modified portions 15 (for example, portions where SiC is separated into Si (silicon) and C (carbon)) are formed inside the ingot 11.

[0044] FIG. 4 is a cross-sectional view schematically showing the ingot 11 after the peeling layer forming step (S1). As shown in FIG. 4, when the modified portion 15 is formed inside the ingot 11 in the peeling layer forming step (S1), the crack 17 can extend from the modified portion 15 along the c-plane 11e. As a result, a peeling layer 19 having the modified portion 15 and the crack 17 is formed inside the ingot 11.

[0045] In the method shown in FIG. 2, ultrasonic waves are applied to the upper surface 11a of the ingot 11 through a liquid layer after the peeling layer forming step (S1) (ultrasonic wave application step: S2). Then, after the peeling layer forming step (S1), the ingot 11 is separated at the peeling layer 19 to peel the wafer (peeling step: S3).

[0046] FIG. 5 is a perspective view schematically showing an example of a peeling device used in the ultrasonic wave application step (S2) and the peeling step (S3). The X2-axis direction and the Y2-axis direction shown in FIG. 5 are directions orthogonal to each other on a horizontal plane, and the Z2-axis direction is a direction (vertical direction) orthogonal to the X2-axis direction and the Y2-axis direction.

[0047] The peeling device 14 shown in FIG. 5 has a columnar table base 16. The lower part of a columnar chuck table 18 is mounted on the central region of the upper part of this table base 16 using a fixture such as a bolt. The diameter of the lower surface of this chuck table 18 is shorter than the diameter of the upper surface of the table base 16.

[0048] Further, the table base 16 is connected to a rotation mechanism (not shown). When the rotation mechanism operates, the table base 16 and the chuck table 18 rotate about a straight line along the Z2-axis direction passing through the center of the upper surface of the chuck table 18 as the rotation axis.

[0049] The upper surface of the chuck table 18 serves as a holding surface for holding the ingot 11. FIG. 6(A) is a top view schematically showing the holding surface of the chuck table 18, and FIG. 6(B) is a cross-sectional view schematically showing the cross-section of the chuck table 18 along the AB line shown in FIG. 6(A).

[0050] The holding surface 20 of the chuck table 18 shown in FIG. 6(A) has a flat circular central region 20a, an annular first groove 20b surrounding the central region 20a, a flat annular intermediate region 20c surrounding the first groove 20b, an annular second groove 20d surrounding the intermediate region 20c, and a flat annular outermost region 20e surrounding the second groove 20d and located at the outermost side of the holding surface 20.

[0051] Furthermore, four openings 22 are provided at substantially equal intervals along the circumferential direction of the holding surface 20 on the bottom surfaces of the first groove 20b and the second groove 20d, respectively. These openings 22 communicate with a suction passage 24 provided inside the chuck table 18, and this suction passage 24 communicates with a suction source (not shown).

[0052] Therefore, when the suction source operates with the ingot 11 placed on the holding surface 20 of the chuck table 18, a suction force acts on the lower surface of the ingot 11 through the suction passage 24, the openings 22, and the first groove 20b and the second groove 20d.

[0053] Thereby, the chuck table 18 sucks and holds the ingot 11. That is, in the holding surface 20 of the chuck table 18, the regions where the first groove 20b and the second groove 20d are provided function as regions (suction regions) for sucking the ingot 11.

[0054] In addition, the radius of the holding surface 20 is designed to be approximately equal to the radius of the ingot 11 in plan view (the distance between a point on the outer peripheral arc-shaped portion and the center). Further, the outer peripheries of the central region 20a, the first groove 20b, the intermediate region 20c, and the second groove 20d are designed to be similar to the outer periphery of the ingot 11 in plan view.

[0055] That is, these outer peripheries include portions that linearly extend corresponding to the orientation flat 13 formed on the side surface of the ingot 11. Further, the linearly extending portions included in these outer peripheries are provided in the same direction when viewed from the center O of the holding surface 20.

[0056] Note that, in order for the chuck table 18 to suck and hold the outer peripheral region of the lower surface of the ingot 11, it is preferable that the width along the radial direction of the holding surface 20 of the outermost region 20e that does not function as a suction region is designed to be as narrow as possible. For example, the width along the radial direction of the holding surface 20 of the outermost region surrounding the arc-shaped portion of the outer periphery of the second groove 20d is designed to be 5% or less of the radius of the holding surface 20. Further, this width is preferably 4% or less of the radius of the holding surface 20, more preferably 3% or less, and most preferably 2% or less.

[0057] In addition, in order to intensively apply the suction force provided from the suction source to the outer peripheral region of the lower surface of the ingot 11, it is preferable that the width along the radial direction of the central region 20a that does not function as a suction region is designed to be as wide as possible. For example, the distance between the arc-shaped portion of the outer periphery of the central region 20a (the arc-shaped portion of the inner periphery of the first groove 20b) and the center O of the holding surface 20 is designed to be 70% or more of the radius of the holding surface 20. Further, this distance is preferably 75% or more of the radius of the holding surface 20, more preferably 80% or more, and most preferably 85% or more.

[0058] Specifically, if the ingot 11 is a 4-inch (diameter 100 mm) ingot, the holding surface 20 may be designed such that the distances D1 to D9 shown in FIG. 6(A) are, for example, as described in the following table.

[0059]

Table 1

[0060] Similarly, if the ingot 11 is a 6-inch (diameter 150 mm) ingot, the holding surface 20 may be designed so that the distances D1 to D9 shown in FIG. 6(A) are, for example, as described in the following table.

[0061]

Table 2

[0062] Furthermore, the upper part of the chuck table 18 including the holding surface 20 is preferably made of a material that does not inhibit the propagation of ultrasonic waves from the ultrasonic application unit described later to the region of the peeling layer 19 located directly above the outer peripheral region of the lower surface 11b of the ingot 11. For example, this upper part is preferably made of stainless steel or the like. Thereby, the ultrasonic waves can be reflected by the holding surface 20 and efficiently propagated to the said region of the peeling layer 19.

[0063] FIG. 7(A) is a top view schematically showing the chuck table 18 holding the ingot 11, and FIG. 7(B) is a side view schematically showing the chuck table 18 holding the ingot 11. As shown in FIGS. 7(A) and 7(B), the ingot 11 is held by the chuck table 18 with the lower part around the arc-shaped portion of the outer periphery of its lower surface 11b being open.

[0064] In this specification, the state where the lower part around the arc-shaped portion of the outer periphery of the lower surface of the ingot is open means that the liquid flowing down from above around this portion flows downwards without staying around this periphery.

[0065] Referring again to FIG. 5, the remaining components of the peeling device 14 will be described. Above the chuck table 18 diagonally, a moving mechanism 26 is provided. This moving mechanism 26 extends along the Y2-axis direction and has a rectangular columnar frame 28 with an opening 28a provided on the side surface on the chuck table 18 side. In this frame 28, a first ball screw (not shown) and a second ball screw (not shown) are accommodated.

[0066] The base end portion of the screw shaft of this first ball screw is connected to the motor 30 through an opening provided at one end (rear end) portion of the frame 28. Similarly, the base end portion of the screw shaft of the second ball screw is connected to the motor 32 through an opening provided at the other end (front end) portion of the frame 28. Further, the base end portions of the first moving plate 34 and the second moving plate 36 are inserted into the opening 28a of the frame 28.

[0067] And the base end portion of the first moving plate 34 is fixed to the nut of the first ball screw. Similarly, the base end portion of the second moving plate 36 is fixed to the nut of the second ball screw. Therefore, when the motor 30 and / or the motor 32 operates, the first moving plate 34 and / or the second moving plate 36 move along the Y2-axis direction within a range where they do not contact each other.

[0068] At the tip of the first moving plate 34, an ultrasonic application unit 38 for applying ultrasonic waves to the upper surface 11a of the ingot 11 is provided. This ultrasonic application unit 38 has a first ultrasonic application unit 40 and a second ultrasonic application unit 42 provided so as to be arranged along the Y2-axis direction.

[0069] The first ultrasonic application unit 40 has an ultrasonic nozzle 44. This ultrasonic nozzle 44 has a hollow truncated cone portion 44a whose width becomes narrower as it approaches the lower end, and a cylindrical portion 44b extending upward from the upper end of the truncated cone portion 44a.

[0070] The frustoconical portion 44a is provided such that the lower end surface of the frustoconical portion 44a faces the upper surface 11a of the ingot 11 held by the chuck table 18, and an opening is provided in this lower end surface. Further, an ultrasonic vibrator is incorporated in the cylindrical portion 44b.

[0071] The tip (lower end) portion of the rod of the air cylinder 46 is fixed to the central region of the upper surface of the cylindrical portion 44b of the ultrasonic nozzle 44. Further, the cylinder side of this air cylinder 46 is fixed to the lower surface side of the tip portion of the first moving plate 34.

[0072] A cylindrical first connection port 48 through which liquid (for example, water) is supplied from a liquid supply source (not shown) via a pipe (not shown), a valve (not shown), etc. is provided at one end (rear end) side of the upper surface of the tip portion of the first moving plate 34.

[0073] The liquid supplied to the first connection port 48 is supplied to a region where vibration by the ultrasonic vibrator incorporated in the cylindrical portion 44b of the ultrasonic nozzle 44 is transmitted through the flow paths provided in the first moving plate 34 and the air cylinder 46.

[0074] Then, the liquid to which the vibration by the ultrasonic vibrator is transmitted is supplied from the opening provided in the lower end surface of the frustoconical portion 44a to the upper surface 11a of the ingot 11 held by the chuck table 18 through the flow path in the ultrasonic nozzle 44.

[0075] Further, the second ultrasonic application unit 42 has a columnar vibration member 50 that is wider than the cylindrical portion 44b of the ultrasonic nozzle 44. This vibration member 50 is provided such that the lower end surface of the vibration member 50 faces the upper surface 11a of the ingot 11 held by the chuck table 18.

[0076] Further, the vibration member 50 incorporates an ultrasonic vibrator similar to the ultrasonic vibrator incorporated in the cylindrical portion 44b of the ultrasonic nozzle 44. And when this ultrasonic vibrator vibrates, the entire vibration member 50 vibrates.

[0077] At the central region of the upper surface of the vibration member 50, the tip (lower end) portion of the rod of the air cylinder 52 is fixed. And the cylinder side of this air cylinder 52 is fixed to the lower surface side of the tip portion of the first moving plate 34.

[0078] On the other end (front end) side of the upper surface of the tip portion of the first moving plate 34, a cylindrical second connection port 54 to which liquid (for example, water) is supplied from a liquid supply source (not shown) via a pipe (not shown), a valve (not shown), etc. is provided.

[0079] The liquid supplied to this second connection port 54 is supplied to a liquid nozzle 56 provided at a position adjacent to the vibration member 50 and the air cylinder 52 in the Y2-axis direction. Further, this liquid passes through the flow path in the liquid nozzle 56 and is supplied to the lower end surface of the vibration member 50 from the opening provided in the lower end surface thereof.

[0080] Also, at the tip portion of the second moving plate 36, a peeling unit 58 for peeling the ingot 11 in the peeling layer 19 and peeling a disk-shaped wafer from the ingot 11 is provided.

[0081] This peeling unit 58 has a suction plate 60 provided with a plurality of suction ports on the lower surface. The plurality of suction ports communicate with a suction source (not shown) such as an ejector via a flow path (not shown) provided inside the suction plate 60, a pipe (not shown) connected to this flow path, a valve (not shown), etc.

[0082] Also, at the central region of the upper surface of the suction plate 60, the tip (lower end) portion of the rod of the air cylinder 62 is fixed. And the cylinder side of this air cylinder 62 is fixed to the lower surface side of the tip portion of the second moving plate 36.

[0083] The ultrasonic application step (S2) is performed, for example, by applying ultrasonic waves to the upper surface 11a of the ingot 11 using the first ultrasonic application unit 40 and then applying ultrasonic waves to the upper surface 11a of the ingot 11 using the second ultrasonic application unit 42.

[0084] FIG. 8(A) is a side view schematically showing a state in which ultrasonic waves are applied to the upper surface 11a of the ingot 11 using the first ultrasonic application unit 40, and FIG. 8(B) is a side view schematically showing a state in which ultrasonic waves are applied to the upper surface 11a of the ingot 11 using the second ultrasonic application unit 42.

[0085] In this ultrasonic application step (S2), first, the ingot 11 is placed on the holding surface 20 of the chuck table 18 so that the upper surface 11a of the ingot 11 after the release layer formation step (S1) faces upward. Next, the suction source is operated so that the outer peripheral region of the lower surface 11b of the ingot 11 is sucked and the ingot 11 is held by the chuck table 4.

[0086] Next, the motor 30 is operated to position the first moving plate 34 above the ingot 11. Next, the air cylinder 46 is operated to lower the rod, and the lower end surface of the frustoconical portion 44a of the ultrasonic nozzle 44 is brought close to the upper surface 11a of the ingot 11.

[0087] Next, with the ultrasonic vibrator built into the cylindrical portion 44b of the ultrasonic nozzle 44 vibrating, the liquid L1 is supplied from the liquid supply source to the ultrasonic nozzle 44. At this time, this liquid L1 is supplied to the upper surface 11a of the ingot 11 through the opening provided in the lower end surface of the frustoconical portion 44a of the ultrasonic nozzle 44 (see FIG. 8(A)).

[0088] Next, while supplying the liquid to the upper surface 11a of the ingot 11, the rotation mechanism is operated to rotate the table base 16 and the chuck table 18. Thereby, ultrasonic waves are applied to a predetermined region (first region) of the upper surface 11a of the ingot 11 using the liquid as a medium.

[0089] Next, the air cylinder 46 is operated to raise the rod, separating the lower end surface of the frustum portion 44a of the ultrasonic nozzle 44 from the upper surface 11a of the ingot 11. Next, the air cylinder 52 is operated to lower the rod, approaching the lower end surface of the vibration member 50 to the upper surface 11a of the ingot 11.

[0090] Next, with the ultrasonic vibrator built into the vibration member 50 vibrating to vibrate the entire vibration member 50, the liquid L2 is supplied from the liquid supply source to the liquid nozzle 56. At this time, this liquid L2 is supplied from the liquid nozzle 56 to the lower end surface of the vibration member 50 (see FIG. 8(B)).

[0091] Next, while supplying liquid to the lower end surface of the vibration member 50, the rotation mechanism is operated to rotate the table base 16 and the chuck table 18. Thereby, ultrasonic waves are applied to a predetermined region (second region) of the upper surface 11a of the ingot 11 using the liquid as a medium. Thus, the ultrasonic application step (S2) is completed.

[0092] Note that the area of the opening provided in the lower end surface of the frustum portion 44a of the ultrasonic nozzle 44 is narrower than the area of the lower end surface of the vibration member 50. Therefore, the area of the second region is wider than the area of the first region.

[0093] Also, in this ultrasonic application step (S2), the ultrasonic vibrators used in the first ultrasonic application unit 40 (ultrasonic nozzle 44) and the second ultrasonic application unit 42 (vibration member 50) vibrate under the same conditions.

[0094] However, the region of the upper surface 11a of the ingot 11 to which ultrasonic waves are applied when using the first ultrasonic application unit 40 (first region) is narrower than the second region to which ultrasonic waves are applied when using the second ultrasonic application unit 42.

[0095] Therefore, the amount of liquid contributing to the application of ultrasonic waves to the upper surface 11a of the ingot 11 is greater when using the second ultrasonic application unit 42 than when using the first ultrasonic application unit 40. For this reason, the energy density of the ultrasonic waves applied to the upper surface 11a of the ingot 11 using the second ultrasonic application unit 42 is lower than the energy density of the ultrasonic waves applied to the upper surface 11a of the ingot 11 using the first ultrasonic application unit 40.

[0096] FIG. 9 is a cross-sectional view schematically showing the ingot 11 after the ultrasonic application step (S2). As shown in FIG. 9, when ultrasonic waves are applied to the upper surface 11a of the ingot 11 in the ultrasonic application step (S2), new cracks are generated in the release layer 19, and the existing cracks further extend.

[0097] Next, the peeling step (S3) is performed. FIGS. 10(A) and 10(B) are side views schematically showing a state in which the ingot 11 is separated at the release layer 19 using the peeling unit 58 to peel the wafer.

[0098] In this peeling step (S3), first, the motor 30 is operated to retract the first moving plate 34 from above the ingot 11, and the motor 32 is operated to position the second moving plate above the ingot 11.

[0099] Next, the air cylinder 62 is operated to lower the rod, bringing the lower surface of the suction plate 60 close to, or into contact with, the upper surface 11a of the ingot 11 (see FIG. 10(A)). Next, a suction source communicating with a plurality of suction ports provided on the lower surface of the suction plate 60 is operated.

[0100] Next, the air cylinder 62 is operated to raise the rod, separating the lower surface of the suction plate 60 from the upper surface 11a of the ingot 11. As a result, the ingot 11 with the upper surface 11a sucked by the suction plate 60 is separated at the release layer 19, and the wafer 21 is peeled off (see FIG. 10(B)).

[0101] In the method shown in FIG. 2, the outer peripheral region of the lower surface 11b of the ingot 11 is sucked, and ultrasonic waves can be applied to the upper surface 11a of the ingot 11 through a liquid layer while the lower part around the arc-shaped portion of the outer periphery of the lower surface 11b of the ingot 11 is open.

[0102] When the outer peripheral region of the lower surface 11b of the ingot 11 is sucked in this way, ultrasonic waves are efficiently propagated to the region of the release layer 19 located directly above the outer peripheral region of the lower surface 11b of the ingot 11, so that the crack propagation in the region of this release layer 19 is not inhibited.

[0103] Also, when the lower part around the arc-shaped portion of the outer periphery of the lower surface 11b of the ingot 11 is open, the liquid serving as the medium for ultrasonic waves does not accumulate around the arc-shaped portion of the outer periphery of the lower surface 11b of the ingot 11.

[0104] As a result, when ultrasonic waves are applied to the upper surface 11a of the ingot 11 through a liquid layer, the release layer 19 formed inside the ingot 11 is not immersed in the liquid. As a result, even when the ingot 11 becomes thin, the ingot 11 can be separated at the release layer 19 and the wafer 21 can be peeled off from the ingot 11.

[0105] Note that the above-described peeling method and peeling device are one aspect of the present invention, and the present invention is not limited to the above-described peeling method and peeling device. For example, in the above-described peeling method, the ultrasonic wave application step (S2) is performed by using the first ultrasonic wave application unit 40 and the second ultrasonic wave application unit 42 in order, but the ultrasonic wave application step (S2) may be performed by using only any one of them.

[0106] In addition, in the above-described peeling method, the ultrasonic transducer (the former) used in the first ultrasonic application unit 40 (ultrasonic nozzle 44) and the ultrasonic transducer (the latter) used in the second ultrasonic application unit 42 (vibrating member 50) were vibrated under the same conditions to perform the ultrasonic application step (S2). However, the conditions for vibrating both may be changed. For example, the conditions for vibrating both may be changed so that the energy density of the ultrasonic wave generated by the vibration of the latter is lower than the energy density of the ultrasonic wave generated by the vibration of the former.

[0107] In addition, in the above-described peeling method, the ultrasonic application step (S2) and the peeling step (S3) were performed using a single peeling device 14. However, in the peeling method of the present invention, both steps may be performed using different devices.

[0108] In addition, in the above-described peeling method, the wafer 21 was peeled off by sucking the upper surface 11a side of the ingot 11 on which the peeling layer 19 was formed. However, the peeling method for peeling the wafer 21 from the ingot 11 in the peeling method of the present invention is not limited to this. For example, the wafer 21 may be peeled off from the ingot 11 by manually pulling the upper surface 11a side of the ingot 11.

[0109] In addition, in the peeling device of the present invention, the holding surface of the chuck table may have any shape as long as it can suck the outer peripheral region of the lower surface 11b of the ingot 11 and apply ultrasonic waves to the upper surface 11a of the ingot 11 through a liquid layer without accumulating liquid around the arc-shaped portion of the outer periphery of the lower surface 11b of the ingot 11. For example, the radius of this holding surface may be designed to be slightly longer or shorter than the radius of the ingot 11 in a plan view (the distance between a point on the arc-shaped portion of the outer periphery and the center).

[0110] Also, when peeling a wafer from an ingot without an orientation flat provided on its side surface, the groove included in the holding surface of the chuck table may not include a portion that linearly extends corresponding to the orientation flat. FIG. 11 is a top view schematically showing the holding surface of such a chuck table.

[0111] The holding surface 64 of the chuck table shown in FIG. 11 has the same structure as the holding surface 20 of the chuck table 18 shown in FIGS. 6(A) and 6(B). However, the holding surface 64 is different from the holding surface 20 in that the outer peripheries of the central region 64a, the first groove 64b, the intermediate region 64c, and the second groove 64d each extend in a perfect circular shape.

[0112] The chuck table having this holding surface 64 is used, for example, in a peeling device when peeling a wafer from a relatively large ingot (for example, an ingot of 8 inches or more) having a notch formed on its side surface.

[0113] Note that, similar to the holding surface 20, the holding surface 64 is preferably designed such that the width along the radial direction of the holding surface 64 in the outermost region 64e is as narrow as possible, and the width along the radial direction of the central region 64a is as wide as possible.

[0114] Specifically, if the ingot held on the holding surface 64 is an 8-inch (diameter 200 mm) ingot, the holding surface 64 may be designed such that the distances D11 to D15 shown in FIG. 11 are, for example, as described in the following table.

[0115]

Table 3

[0116] In addition, the structures and methods according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention.

Explanation of Reference Numerals

[0117] 11: Ingot (11a: upper surface, 11b: lower surface, 11c: c-axis) (11d: perpendicular line, 11e: c-plane) 13: Orientation flat 15: Modification part 17: Crack 19: Release layer 21: Wafer 2: Laser irradiation device 4: Chuck table 6: Laser irradiation unit 8: Head 10: Connection part 12: Imaging unit 14: Release device 16: Table base 18: Chuck table 20: Holding surface (20a: central region, 20b: first groove, 20c: intermediate region) (20d: second groove, 20e: outermost region) 22: Opening 24: Suction path 26: Moving mechanism 28: Frame body (28a: opening) 30: Motor 32: Motor 34: First moving plate 36: Second moving plate 38: Ultrasonic application unit 40: First ultrasonic application unit 42: Second ultrasonic application unit 44: Ultrasonic nozzle (44a: frustum part, 44b: cylindrical part) 46: Air cylinder 48: First connection port 50: Vibration member 52: Air cylinder 54: Second connection port 56: Liquid nozzle 58: Release unit 60: Suction plate 62: Air cylinder 64: Holding surface (64a: Central region, 64b: First groove, 64c: Intermediate region) (64d: Second groove, 64e: Outermost region)

Claims

1. A peeling method for peeling a disk-shaped wafer from a columnar ingot having a peeling layer formed therein by separating the ingot at the peeling layer, comprising: a step of applying ultrasonic waves to the upper surface of the ingot through a liquid layer in a state where the outer peripheral region of the lower surface of the ingot is sucked and the lower part around the arc-shaped part of the outer periphery of the lower surface of the ingot is open, so that the liquid flowing down along the side surface of the ingot from above around the part does not stay around the part but flows downwards.

2. A peeling method for peeling a disk-shaped wafer from a columnar ingot having a peeling layer formed therein by separating the ingot at the peeling layer, comprising: a step of applying ultrasonic waves to the upper surface of the ingot through a liquid layer in a state where the outer peripheral region of the lower surface of the ingot is sucked and the lower part around the arc-shaped part of the outer periphery of the lower surface of the ingot is open, wherein the step of applying ultrasonic waves is carried out in a state where the ingot is held on the holding surface of a chuck table, and the radius of the holding surface is designed to be approximately equal to the radius of the ingot in a plan view.

3. A method for manufacturing a wafer for manufacturing a disk-shaped wafer by separating a columnar ingot having a peeling layer formed therein at the peeling layer, comprising: a step of applying ultrasonic waves to the upper surface of the ingot through a liquid layer in a state where the outer peripheral region of the lower surface of the ingot is sucked and the lower part around the arc-shaped part of the outer periphery of the lower surface of the ingot is open, so that the liquid flowing down along the side surface of the ingot from above around the part does not stay around the part but flows downwards; and a peeling step of separating the ingot at the peeling layer to peel the wafer from the ingot after the step of applying ultrasonic waves.

4. A method for manufacturing a wafer for manufacturing a disk-shaped wafer by separating a columnar ingot having a peeling layer formed therein at the peeling layer, comprising: An ultrasonic application step of applying ultrasonic waves to the upper surface of the ingot through a liquid layer while the outer peripheral region of the lower surface of the ingot is sucked and the lower part around the arc-shaped portion of the outer periphery of the lower surface of the ingot is open; A peeling step of separating the ingot in the peeling layer after the ultrasonic application step to peel the wafer from the ingot, including; The ultrasonic application step is performed while the ingot is held on the holding surface of the chuck table; A method for manufacturing a wafer, characterized in that the radius of the holding surface is designed to be approximately equal to the radius of the ingot in a plan view.

5. A peeling device for separating a columnar ingot formed with a peeling layer in the peeling layer to peel a disk-shaped wafer from the ingot, An ultrasonic application unit for applying ultrasonic waves to the upper surface of the ingot through a liquid layer; A chuck table having a circular holding surface for sucking and holding the outer peripheral region of the lower surface of the ingot, comprising; The holding surface is A flat circular central region; An annular suction region surrounding the central region and communicating with a suction source through a suction path; An annular outermost region surrounding the suction region and located at the outermost side of the holding surface, having; The width along the radial direction of the holding surface of the outermost region surrounding the arc-shaped portion of the outer periphery of the suction region is 5% or less of the radius of the holding surface; A peeling device, characterized in that the distance between the arc-shaped portion of the outer periphery of the central region and the center of the holding surface is 70% or more of the radius of the holding surface.

6. A peeling device for separating a columnar ingot formed with a peeling layer in the peeling layer to peel a disk-shaped wafer from the ingot, An ultrasonic application unit for applying ultrasonic waves to the upper surface of the ingot through a liquid layer; A chuck table having a circular holding surface for sucking and holding the outer peripheral region of the lower surface of the ingot, comprising; The holding surface is A flat circular central region; An annular suction region surrounding the central region and communicating with a suction source through a suction path; An annular outermost region surrounding the suction region and located at the outermost side of the holding surface, having; The width along the radial direction of the holding surface of the outermost region surrounding the arc-shaped portion of the outer periphery of the suction region is 5% or less of the radius of the holding surface; The attracting region attracts the outer peripheral region of the lower surface of the ingot, and the lower part around the arc-shaped portion of the outer periphery of the lower surface of the ingot is opened without being blocked by the outermost region, so that the liquid flowing down along the side surface of the ingot from above around the portion does not stay around the portion but flows downwards. An ultrasonic wave is applied to the upper surface of the ingot through a liquid layer. A peeling device characterized by this.

7. The upper part of the chuck table including the holding surface is made of stainless steel. The peeling device according to claim 5 or 6, characterized by this.

8. The ultrasonic wave applying unit A first ultrasonic wave applying unit that applies ultrasonic waves to a first region on the upper surface of the ingot with a first energy density; A second ultrasonic wave applying unit that applies ultrasonic waves to a second region wider than the first region on the upper surface of the ingot with a second energy density lower than the first energy density; The peeling device according to any one of claims 5 to 7, characterized by including this.

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