Method for manufacturing wafer and processing device

Abstract

To provide a method for manufacturing a wafer which can reduce the time required to manufacture the upper limit of the numbers of wafers from each ingot while processing a plurality of ingots at the same time.SOLUTION: In a planarization step as one of a series of steps to manufacture wafers from ingots, an ingot is polished until the thickness of the ingot becomes smaller than the thickness of the ingot when the series of steps are started, by the thickness obtained by adding the finished thickness of wafers, the assumed thickness of a separation layer, and the distribution thickness obtained by dividing the excessive thickness of the ingot by the number obtained by subtracting one from the upper limit of the numbers of wafers that can be manufactured from the ingot.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a wafer manufacturing method for manufacturing three or more wafers from an ingot, and a processing apparatus therefor. [Background technology]

[0002] Semiconductor device chips are generally manufactured using wafers made of single crystals of silicon (Si), silicon carbide (SiC), gallium nitride (GaN), lithium tantalate (LiTaO3:LT), lithium niobate (LiNbO3:LN), etc. The wafers are manufactured by cutting them from ingots using, for example, a wire saw.

[0003] However, when cutting a wafer from an ingot using a wire saw, the cutting allowance is relatively large, about 300 μm. In addition, the surface of the wafer cut in this way has fine irregularities, and the wafer is curved overall (the wafer is warped). Therefore, when using the wafer to manufacture chips, the surface of the wafer needs to be flattened by lapping, etching, and / or polishing.

[0004] In this case, the amount of material that is finally used as wafers is about 2 / 3 of the total amount of the ingot. In other words, about 1 / 3 of the total amount of the ingot is discarded when cutting the wafers from the ingot and when flattening the wafer surface. Therefore, the productivity is low when manufacturing wafers using a wire saw in this way.

[0005] In view of this, a wafer manufacturing method has been proposed in which a laser beam having a wavelength that transmits through the material of an ingot is used to manufacture a wafer from the ingot (see, for example, Patent Document 1). Specifically, in this method, first, the focal point of the laser beam is irradiated onto the ingot while the focal point and the ingot are moved relatively to each other so that the focal point is positioned inside the ingot.

[0006] As a result, a separation layer including a modified portion and a crack extending from the modified portion is formed inside the ingot. Then, in this method, an external force is applied to the ingot so as to further extend the crack. As a result, the ingot is separated at the separation layer to produce a wafer.

[0007] Furthermore, when a wafer is manufactured from an ingot in this manner, a separation layer (ingot-side remaining separation layer and wafer-side remaining separation layer) remains on each of the ingot and the wafer. Therefore, in the above-described wafer manufacturing method, the ingot and the wafer are ground to remove the ingot-side remaining separation layer and the wafer-side remaining separation layer, respectively, and the ingot and the wafer are flattened. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2019-12765 A Summary of the Invention [Problem to be solved by the invention]

[0009] When the above-described wafer manufacturing process is repeated, an ingot may be left with a thickness slightly less than that required to produce two wafers, in which case the final wafer is produced by grinding the ingot down to the finished wafer thickness over an extended period of time.

[0010] However, when multiple ingots are processed in parallel to produce the maximum number of wafers from each ingot, the grinding process may take a long time to produce the final wafer from each ingot, which may cause a bottleneck, i.e., when grinding a particular ingot to produce the final wafer, the processing of other ingots may be stopped for a long time.

[0011] In view of this, an object of the present invention is to provide a wafer manufacturing method and processing apparatus therefor that can reduce the time required to manufacture an upper limit number of wafers from each ingot while simultaneously processing multiple ingots in parallel. [Means for solving the problem]

[0012] According to one aspect of the present invention, there is provided a method for producing three or more wafers from an ingot by repeating a series of steps including a separation layer forming step of forming a separation layer inside an ingot, a separation step of producing wafers by separating the ingot at the separation layer after the separation layer forming step, and a planarization step of removing an ingot-side remaining separation layer remaining in the ingot and a wafer-side remaining separation layer remaining in the wafer after the separation step, thereby planarizing the ingot and the wafer, respectively. Prior to producing the three or more wafers from the ingot, the method includes determining an upper limit number of the wafers that can be produced from the ingot by referring to an initial thickness of the ingot, a finished thickness of the wafer, and an expected thickness of the separation layer. and an excess thickness of the ingot, in which in the separation layer forming step, the separation layer is formed by relatively moving the ingot and a laser beam having a wavelength that transmits through the material of the ingot while irradiating the ingot with a laser beam so that the focal point of the laser beam is positioned at a predetermined depth from the surface of the ingot, and in the planarizing step, the ingot is ground until the thickness of the ingot is thinner than the thickness of the ingot at the time of starting the series of steps by a thickness obtained by adding the finishing thickness, the expected thickness, and a distributed thickness obtained by dividing the excess thickness by a number obtained by subtracting 1 from the upper limit number, and the wafer is ground until the wafer reaches the finishing thickness.

[0013] Furthermore, the predetermined depth is preferably a depth corresponding to a first thickness obtained by adding the finishing thickness and the thickness of the wafer-side remaining separation layer. Alternatively, the predetermined depth is preferably a depth corresponding to a second thickness obtained by adding the finishing thickness, the thickness of the wafer-side remaining separation layer, and the distributed thickness. Alternatively, the predetermined depth is preferably a depth longer than the first thickness obtained by adding the finishing thickness and the thickness of the wafer-side remaining separation layer, and shorter than the second thickness obtained by adding the first thickness and the distributed thickness.

[0014] According to another aspect of the present invention, a processing apparatus for manufacturing three or more wafers from an ingot includes a laser processing unit for forming a separation layer inside the ingot, a separating unit for manufacturing the wafers by separating the ingot at the separation layer, a planarizing unit for removing an ingot-side remaining separation layer remaining in the ingot to planarize the ingot, and a controller for controlling the laser processing unit, the separating unit, and the planarizing unit to repeat a series of steps including the formation of the separation layer, the separation of the ingot, and the planarization of the ingot a number of times obtained by subtracting 1 from an upper limit number of the wafers that can be manufactured from the ingot, and the controller includes a memory for storing an initial thickness of the ingot, a finished thickness of the wafer, and an expected thickness of the separation layer, and a processor for calculating the upper limit number and an excess thickness of the ingot by referring to the thickness, the finished thickness, and the estimated thickness, wherein the processor controls the laser processing unit so that the separation layer is formed by relatively moving the ingot and the laser beam while irradiating the ingot with a laser beam having a wavelength that transmits through the material of the ingot so that the focal point at which the laser beam is focused is positioned at a predetermined depth from the surface of the ingot, and controls the flattening unit so that the ingot is ground to a thickness thinner than the thickness of the ingot at the time when the series of steps is started by a thickness obtained by adding the finished thickness, the estimated thickness, and a distributed thickness obtained by dividing the excess thickness by a number obtained by subtracting 1 from the upper limit number. Effect of the Invention

[0015] In the present invention, in a planarization step (specifically, planarization of the ingot) included in a series of steps for producing wafers from an ingot, the ingot is ground until its thickness is thinner than the thickness of the ingot at the start of the series of steps by a thickness obtained by adding together the finished thickness of the wafer, the expected thickness of the separation layer, and a distributed thickness obtained by dividing the excess thickness of the ingot by a number obtained by subtracting 1 from the maximum number of wafers that can be produced from the ingot.

[0016] Then, when this series of steps is repeated, an ingot having a thickness greater than or equal to the minimum thickness of the ingot required to produce the final wafer (specifically, the thickness obtained by adding the finishing thickness of the wafer and the thickness of the remaining separation layer on the ingot side) and less than or equal to the thickness obtained by adding the minimum thickness of the ingot required to produce the final wafer and the distributed thickness is subjected to the final flattening step.

[0017] In this case, the time required to manufacture the final wafer is shortened by grinding the ingot until it has the finishing thickness of the wafer. Therefore, by applying the present invention as a method for manufacturing the upper limit number of wafers from each ingot while simultaneously processing multiple ingots in parallel, grinding the ingots to manufacture the final wafer from each ingot is less likely to become a bottleneck, and the time required can be reduced. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1(A) is a perspective view that shows a schematic diagram of an example of an ingot, and FIG. 1(B) is a side view that shows a schematic diagram of the ingot shown in FIG. 1(A). [Diagram 2] FIG. 2 is a flow chart that illustrates a schematic example of a wafer manufacturing method for manufacturing three or more wafers from the ingot shown in FIGS. 1(A) and 1(B). [Diagram 3] FIG. 3 is a side view diagrammatically showing parameters referred to in a calculation step included in the method for manufacturing the wafer shown in FIG. [Figure 4] FIG. 4 is a perspective view diagrammatically illustrating a separation layer forming step included in the method for producing the wafer shown in FIG. [Diagram 5] 5(A) is a partially enlarged cross-sectional view showing a schematic view of an ingot after a separation layer formation step included in the wafer manufacturing method shown in FIG. 2, and FIG. 5(B) is a plan view showing a schematic view of an ingot after a separation layer formation step included in the wafer manufacturing method shown in FIG. 2. [Figure 6] 6(A) and 6(B) are each a side view diagrammatically illustrating the state of a separation step included in the method for producing the wafer shown in FIG. [Figure 7] FIG. 7 is a perspective view showing a non-final planarization step included in the method for producing the wafer shown in FIG. [Figure 8] FIG. 8 is a block diagram that illustrates a schematic example of a processing apparatus for producing three or more wafers from the ingot illustrated in FIGS. 1(A) and 1(B). [Figure 9] FIG. 9 is a block diagram that illustrates a schematic diagram of another example of a processing apparatus for producing three or more wafers from the ingot illustrated in FIGS. 1(A) and 1(B). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1(A) is a perspective view showing an example of an ingot, and Fig. 1(B) is a side view showing the ingot shown in Fig. 1(A). The ingot 11 shown in Fig. 1(A) and Fig. 1(B) is made of, for example, a single crystal of SiC, and has a cylindrical shape including a front surface 11a and a back surface 11b that are approximately parallel to each other.

[0020] The ingot 11 is manufactured by epitaxial growth. In order to reduce lattice defects formed inside the ingot 11, the ingot 11 is manufactured so that the c-axis 11c of SiC is slightly tilted with respect to the perpendicular line 11d of the front surface 11a and the back surface 11b. For example, the angle (off angle) α between the c-axis 11c and the perpendicular line 11d is 1° to 6° (typically 4°).

[0021] Furthermore, two flat portions for indicating the crystal orientation of SiC, namely, a primary orientation flat 13 and a secondary orientation flat 15, are formed on the side surface of the ingot 11. The primary orientation flat 13 is longer than the secondary orientation flat 15. The secondary orientation flat 15 is formed so as to be parallel to an intersection line where a plane parallel to the c-plane 11e of SiC intersects with the front surface 11a or the back surface 11b.

[0022] Ingot 11 may be made of a single crystal of a material other than SiC (e.g., Si, GaN, LT, or LN, etc.). Ingot 11 may not have one or both of primary orientation flat 13 and secondary orientation flat 15 on its side surface, and may have a notch formed therein to indicate the crystal orientation of the material constituting ingot 11 instead.

[0023] 2 is a flow chart that illustrates an example of a wafer manufacturing method for manufacturing three or more wafers from an ingot 11. In short, in this method, n wafers are manufactured from an ingot 11 by repeating a series of steps for separating and flattening the ingot 11 by a number (n-1) obtained by subtracting 1 from the upper limit number n (n is a natural number equal to or greater than 3) of wafers that can be manufactured from the ingot 11.

[0024] Furthermore, in this method, the removal of excess thickness (i.e., the thickness in excess of the thickness required to produce n wafers) of ingot 11 is distributed over a series of steps performed (n-1) times, rather than being performed all at once in the series of steps performed to produce the final wafer.

[0025] Specifically, in this method, in each series of steps, the thickness of the ingot 11 is reduced by a thickness obtained by adding together the minimum thickness of the ingot 11 that is reduced during the manufacture of the wafer (specifically, a thickness obtained by adding together the finished thickness of the wafer described below and the expected thickness of the separation layer) and the distributed thickness (specifically, a thickness obtained by dividing the excess thickness by (n-1)).

[0026] 2, first, the upper limit number n of wafers that can be manufactured from an ingot 11 and the excess thickness of the ingot 11 are calculated with reference to previously determined parameters (calculation step S1). Fig. 3 is a side view that illustrates the parameters referred to in the calculation step S1.

[0027] In this calculation step S1, the initial thickness T0 of the ingot 11, the finished thickness T1 of the wafer (i.e., the thickness of the wafer after planarization in the non-final planarization step S5 and the final planarization step S6 described below), and the assumed thickness T2 of the separation layer (i.e., the thickness assumed to be possessed by the separation layer formed inside the ingot 11 in the separation layer formation step S2 described below) are referenced.

[0028] Specifically, in this method, the ingot 11 is separated into a number (n-1) obtained by subtracting 1 from the upper limit number n of wafers that can be produced from the ingot 11. Therefore, the initial thickness T0 of the ingot 11 becomes a value that satisfies the following inequalities (1) and (2).

number

number

[0029] Then, by modifying the above inequalities (1) and (2), it is found that the upper limit number n of wafers that can be produced from the ingot 11 is a natural number that satisfies the following inequality (3).

number

[0030] Moreover, if the upper limit number n of wafers that can be produced from the ingot 11 is calculated, the excess thickness T3 of the ingot 11 expressed by the following formula (4) can also be calculated.

number

[0031] Furthermore, once the upper limit number n of wafers that can be produced from the ingot 11 and the excess thickness T3 of the ingot 11 are calculated, it becomes possible to calculate the distributed thickness ΔT of the ingot 11, which is expressed by the following formula (5).

number

[0032] For example, if the initial thickness T0 of the ingot 11 is 20 mm (20,000 μm), the finished thickness T1 of the wafer is 350 μm, and the expected thickness T2 of the separation layer is 80 μm, the upper limit number n of wafers that can be manufactured from the ingot 11 is 46, and the excess thickness T3 of the ingot 11 is 300 μm. Furthermore, in this case, the distributed thickness ΔT of the ingot 11 is 6.67 μm.

[0033] After the calculation step S1, a separation layer is formed inside the ingot 11 (separation layer forming step S2). Fig. 4 is a perspective view showing the separation layer forming step S2. Note that the X-axis direction and the Y-axis direction shown in Fig. 4 are directions perpendicular to each other on a horizontal plane, and the Z-axis direction is a direction (vertical direction) perpendicular to the X-axis direction and the Y-axis direction.

[0034] This separation layer forming step S2 is performed in a laser processing device 2. The laser processing device 2 includes a chuck table 4 having a circular holding surface that is approximately parallel to a horizontal plane and capable of holding an ingot 11 on this holding surface.

[0035] The chuck table 4 is connected to a suction mechanism (not shown). This suction mechanism has, for example, an ejector. When the suction mechanism operates, a suction force acts on the space near the holding surface of the chuck table 4. Therefore, when the suction mechanism operates with the ingot 11 placed on the holding surface, the ingot 11 is held on the holding surface of the chuck table 4.

[0036] The chuck table 4 is connected to a rotation mechanism (not shown). The rotation mechanism includes, for example, a pulley and a motor. When the rotation mechanism operates, the chuck table 4 rotates about a rotation axis that is a straight line passing through the center of the holding surface along the Z-axis direction.

[0037] A head 8 of the laser beam irradiation unit 6 is provided above the chuck table 4. This head 8 is provided at the tip of a cylindrical housing 10 extending along the Y-axis direction. The head 8 houses an optical system such as a condenser lens and a mirror, and the housing 10 houses an optical system such as a mirror and / or a lens.

[0038] The base end of the housing 10 is connected to a movement mechanism. This movement mechanism has, for example, a ball screw and a motor. When the movement mechanism operates, the head 8 and the housing 10 move along the X-axis, Y-axis, and / or Z-axis directions.

[0039] The laser beam irradiation unit 6 also has a laser oscillator (not shown) that generates a laser beam with a wavelength (e.g., 1064 nm) that transmits through the material of the ingot 11. This laser oscillator has a laser medium such as Nd:YAG. When the laser beam is generated by the laser oscillator, the laser beam is emitted toward the holding surface of the chuck table 4 via an optical system contained in the housing 10 and the head 8.

[0040] Furthermore, an imaging unit 12 capable of capturing an image of the holding surface side of the chuck table 4 is provided on the side of the housing 10. The imaging unit 12 has 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.

[0041] When performing the separation layer forming step S2 in the laser processing apparatus 2, first, the ingot 11 is placed on the holding surface of the chuck table 4 with the surface 11a facing up. Next, the suction mechanism is operated so that the ingot 11 is held on the chuck table 4. Next, based on an image of the surface 11a of the ingot 11 formed by imaging by the imaging unit 12, etc., the rotation mechanism rotates the chuck table 4 so that the secondary orientation flat 15 is parallel to the X-axis direction.

[0042] Next, the movement mechanism moves the head 8 and the housing 10 along the X-axis direction and / or the Y-axis direction so that a region of the ingot 11 slightly inside the secondary orientation flat 15 is positioned in the X-axis direction when viewed in a plan view from the head 8. Next, the movement mechanism moves the head 8 and the housing 10 along the Z-axis direction so that the focal point at which the laser beam emitted from the head 8 is focused is positioned at a predetermined depth from the surface 11a of the ingot 11.

[0043] The predetermined depth is set with reference to a parameter that is known in advance. Specifically, the predetermined depth is set to be equal to or greater than a thickness (first thickness) obtained by adding the finishing thickness T1 of the wafer and the thickness of the separation layer (wafer-side remaining separation layer) remaining on the wafer after the wafer is separated from the ingot 11, and equal to or less than a thickness (second thickness) obtained by adding the first thickness and the distributed thickness ΔT of the ingot 11. The thickness of the wafer-side remaining separation layer is, in short, a thickness corresponding to a thickness obtained by subtracting the thickness of the separation layer (ingot-side remaining separation layer) remaining on the ingot 11 after the wafer is separated from the ingot 11 from the assumed thickness T2 of the separation layer.

[0044] Next, while emitting a laser beam from head 8, the moving mechanism moves head 8 and housing 10 along the X-axis direction so that the focal point at which the laser beam is focused passes from one end to the other end in the X-axis direction of ingot 11. In other words, while irradiating ingot 11 with the laser beam, the focal point at which the laser beam is focused and ingot 11 are moved relatively along the intersection line where a plane parallel to c-plane 11e of the material of ingot 11 (here, SiC) intersects with surface 11a.

[0045] Next, the moving mechanism moves the head 8 and the housing 10 along the Y-axis direction so that the head 8 is positioned in the X-axis direction when viewed in a plan view from a region slightly farther from the secondary orientation flat 15 than the region already irradiated with the laser beam. Next, the laser beam is irradiated again onto the ingot 11 as described above.

[0046] Furthermore, the movement of the head 8 and the housing 10 along the Y-axis direction and the irradiation of the laser beam onto the ingot 11 are repeated until the irradiation of the laser beam onto the region of the ingot 11 that is farthest from the secondary orientation flat 15 is completed, thereby completing the separation layer formation step S2.

[0047] Fig. 5(A) is a partially enlarged cross-sectional view showing the ingot 11 after the separation layer forming step S2, and Fig. 5(B) is a plan view showing the ingot 11 after the separation layer forming step S2. In the separation layer forming step S2, a modified portion 17 in which the crystal structure of the material of the ingot 11 (here, SiC) is disturbed is formed inside the ingot 11, centered on the focal point where the laser beam is focused.

[0048] Furthermore, when modified regions 17 are formed inside ingot 11, the volume of ingot 11 expands, causing internal stress in ingot 11. This internal stress is alleviated by the propagation of cracks 19 from modified regions 17. Note that these cracks 19 mainly propagate along c-plane 11e. As a result, a separation layer 21 including a plurality of modified regions 17 and cracks 19 propagating from each of the plurality of modified regions 17 is formed inside ingot 11.

[0049] After the separation layer forming step S2, the ingot 11 is separated at the separation layer 21 to produce wafers (separation step S3). Each of Fig. 6(A) and Fig. 6(B) is a side view showing the separation step S3. This separation step S3 is performed in a separation apparatus 14. The separation apparatus 14 includes a chuck table 16 having a structure similar to that of the chuck table 4 shown in Fig. 4.

[0050] The chuck table 16 is connected to a table-side suction mechanism (not shown). The table-side suction mechanism has, for example, a vacuum pump. When the table-side suction mechanism operates, a suction force acts on the space near the holding surface of the chuck table 16. Therefore, when the table-side suction mechanism operates with the ingot 11 placed on the holding surface, the ingot 11 is held on the holding surface of the chuck table 16.

[0051] A separation unit 18 is provided above the chuck table 16. This separation unit 18 has a suction plate 20 having a plurality of suction ports formed on the lower surface thereof. The plurality of suction ports communicate with a separation unit side suction mechanism such as a vacuum pump via suction paths formed inside the suction plate 20. When the separation unit side suction mechanism operates, a suction force acts on the space near the lower surface of the suction plate 20.

[0052] In addition, an upper portion of the suction plate 20 is connected to a vertical movement mechanism 22. This vertical movement mechanism 22 has, for example, an air cylinder, etc. When the vertical movement mechanism 22 operates, the suction plate 20 moves in the vertical direction.

[0053] When performing the separation step S3 in the separation device 14, first, the ingot 11 having the separation layer 21 formed therein is placed on the holding surface of the chuck table 16 with the surface 11a facing up, with the chuck table 16 and the suction plate 20 being sufficiently separated from each other. Next, the table-side suction mechanism is operated so that the ingot 11 is held on the chuck table 16.

[0054] Next, the vertical movement mechanism lowers the suction plate 20 so that the lower surface of the suction plate 20 contacts the front surface 11a of the ingot 11 (see FIG. 6(A)). Next, the separation unit side suction mechanism is operated so that the front surface 11a side of the ingot 11 is sucked upward.

[0055] Next, the vertical movement mechanism raises the suction plate 20 so as to separate the suction plate 20 from the chuck table 16 (see FIG. 6(B)). At this time, a tensile stress acts on the ingot 11, and the cracks 19 included in the separation layer 21 further extend.

[0056] As a result, the ingot 11 is separated at the separation layer 21 to produce an ingot 11 having an ingot-side remaining separation layer on its surface 11a side, and a wafer 23 having a wafer-side remaining separation layer on one side thereof. Note that the surface 11a of the ingot 11 and one side of the wafer 23 each have an uneven shape that reflects the distribution of the modified portions 17 and cracks 19 in the separation layer 21. This completes the separation step S3.

[0057] Then, if the ingot 11 has not been separated (n-1) times (step S4: NO), the ingot 11 is ground to a predetermined thickness to remove the remaining separation layer on the ingot side and flatten the ingot 11, and the wafer is ground to a finishing thickness T1 to remove the remaining separation layer on the wafer side and flatten the wafer 23 (non-final flattening step S5).

[0058] In addition, this specified thickness is thinner than the thickness of ingot 11 at the time when a series of steps including separation layer formation step S2, separation step S3, and non-final flattening step S5 are started (i.e., at the time when separation layer formation step S2 is started) by the sum of the finished thickness T1 of wafer 23, the estimated thickness T2 of separation layer 21, and the distributed thickness ΔT of ingot 11.

[0059] 7 is a perspective view showing the non-final planarization step S5 in a schematic manner. This non-final planarization step S5 is performed in a grinding device 24. The grinding device 24 has a holding surface having a shape corresponding to the side surface of a cone whose center protrudes slightly beyond the outer edge, and has a chuck table 26 capable of holding the wafer 23 on this holding surface.

[0060] The chuck table 26 is connected to a suction mechanism. This suction mechanism has an ejector and the like. When the suction mechanism operates, a suction force acts on the space near the holding surface of the chuck table 26. Therefore, when the suction mechanism operates with the ingot 11 or the wafer 23 placed on the holding surface, the ingot 11 or the wafer 23 is held on the holding surface of the chuck table 26.

[0061] Furthermore, the chuck table 26 is connected to a horizontal movement mechanism. The horizontal movement mechanism has, for example, a ball screw and a motor. When the horizontal movement mechanism operates, the chuck table 26 moves in the horizontal direction.

[0062] The chuck table 26 is connected to a rotation mechanism (not shown). The rotation mechanism includes, for example, a pulley and a motor. When the rotation mechanism operates, the chuck table 26 rotates about a rotation axis that is a straight line passing through the center of the holding surface.

[0063] A measuring unit (not shown) is provided near the chuck table 26. The measuring unit has, for example, a contact or non-contact thickness gauge. The measuring unit can measure the thickness of the ingot 11 or the wafer 23 held on the holding surface of the chuck table 26.

[0064] A grinding unit 28 is provided above the chuck table 26. The grinding unit 28 has a spindle 30 whose upper end is connected to a motor. A disk-shaped mount 32 is provided at the lower end of the spindle 30, and a grinding wheel 34 is attached to the mount 32.

[0065] The grinding wheel 34 has an annular base 36 and a plurality of grinding stones 38 arranged at intervals along the circumferential direction of the base 36. The lower surfaces of the grinding stones 38 are arranged at approximately the same height, and these lower surfaces serve as grinding surfaces for grinding the ingot 11 and the wafer 23.

[0066] Furthermore, the spindle 30 is connected to a vertical movement mechanism. This vertical movement mechanism has, for example, a ball screw and a motor. When the vertical movement mechanism operates, the spindle 30, the mount 32, and the grinding wheel 34 move in the vertical direction.

[0067] When the non-final planarization step S5 is performed in the grinding device 24, for example, the ingot 11 is ground to the above-mentioned predetermined thickness, and then the wafer 23 is ground to the finishing thickness T1. In this case, first, the ingot 11 is placed on the holding surface of the chuck table 26 with the surface 11a facing up, with the chuck table 26 and the grinding wheel 34 sufficiently spaced apart from each other in both the horizontal and vertical directions.

[0068] Next, the suction mechanism is operated so that the ingot 11 is held on the chuck table 26. Next, the horizontal movement mechanism moves the chuck table 26 so that the center of the holding surface of the chuck table 26 and the trajectories of the multiple grinding stones 38 when the grinding wheel 34 is rotated together with the spindle 30 overlap in the vertical direction.

[0069] Next, the rotation mechanism is operated to rotate the chuck table 26, and the motor connected to the upper end of the spindle 30 is operated to rotate the grinding wheel 34. Next, the vertical movement mechanism lowers the spindle 30, the mount 32, and the grinding wheel 34 so that the grinding surface of any one of the multiple grinding wheels 38 contacts the surface 11a of the ingot 11.

[0070] This starts grinding of the ingot 11. Then, this grinding, i.e., the lowering of the grinding wheel 34 while rotating both the chuck table 26 and the grinding wheel 34, is continued until the thickness of the ingot 11 measured by the measuring unit reaches the above-mentioned predetermined thickness.

[0071] Once grinding of the ingot 11 is completed, the rotation of both the chuck table 26 and the grinding wheel 34 is stopped, and the horizontal movement mechanism and vertical movement mechanism are operated to sufficiently separate the chuck table 26 and the grinding wheel 34 in the horizontal and vertical directions, respectively.

[0072] Next, the wafer 23 is ground to the finishing thickness T1 in the same manner as described above. This completes the non-final flattening step S5. In the non-final flattening step S5, either the grinding of the ingot 11 or the grinding of the wafer 23 may be performed in a grinding machine other than the grinding machine 24. In this case, both grinding operations can be performed in parallel.

[0073] In addition, the thickness of the ingot 11 and the thickness of the wafer 23 removed in the non-final flattening step S5 vary depending on the above-mentioned specified depth (i.e., the distance between the focal point of the laser beam irradiated to the ingot 11 in the separation layer formation step S2 and the surface 11a of the ingot 11).

[0074] Specifically, when the specified depth corresponds to the above-mentioned first thickness (i.e., the thickness obtained by adding the finishing thickness T1 of the wafer and the thickness of the remaining separation layer on the wafer side), the thickness of the ingot 11 removed in the non-final flattening step S5 corresponds to the thickness obtained by adding the thickness of the remaining separation layer on the ingot side and the distributed thickness ΔT of the ingot 11, and the thickness of the wafer 23 removed in the non-final flattening step S5 corresponds to the thickness of the remaining separation layer on the wafer side.

[0075] In this case, even if the crack 19 unintentionally extends long toward the back surface 11b of the ingot 11 in the separation layer formation step S2 and the separation step S3, there is a high probability that the ingot 11 can be flattened without the crack 19 remaining in the ingot 11.

[0076] Furthermore, when the specified depth corresponds to the second thickness described above (i.e., the thickness obtained by adding the first thickness described above and the distributed thickness ΔT of the ingot 11), the thickness of the ingot 11 removed in the non-final flattening step S5 corresponds to the thickness of the remaining separation layer on the ingot side, and the thickness of the wafer 23 removed in the non-final flattening step S5 corresponds to the thickness obtained by adding the thickness of the remaining separation layer on the wafer side and the distributed thickness ΔT of the ingot 11.

[0077] In this case, even if the crack 19 unintentionally extends long toward the surface 11a of the ingot 11 in the separation layer formation step S2 and the separation step S3, there is a high probability that the wafer 23 can be flattened without the crack 19 remaining in the wafer 23.

[0078] Furthermore, when the specified depth is longer than the above-mentioned first thickness and shorter than the above-mentioned second thickness, the thickness of the ingot 11 removed in the non-final flattening step S5 corresponds to the thickness obtained by adding the thickness of the remaining separation layer on the ingot side to the thickness obtained by multiplying the distributed thickness ΔT of the ingot 11 by (k / k+1) (k is a positive real number), and the thickness of the wafer 23 removed in the non-final flattening step S5 corresponds to the thickness obtained by adding the thickness of the remaining separation layer on the wafer side to the thickness obtained by multiplying the distributed thickness ΔT of the ingot 11 by (1 / k+1).

[0079] In this case, even if the crack 19 unintentionally extends to some extent toward both the front surface 11a and the back surface 11b of the ingot 11 in the separation layer formation step S2 and the separation step S3, there is a high probability that the crack 19 will not remain in either the ingot 11 or the wafer 23, and both the ingot 11 and the wafer 23 will be flattened.

[0080] After the non-final flattening step S5, the above-mentioned separation layer forming step S2 and separation step S3 are performed again. Furthermore, the above-mentioned non-final flattening step S5, separation layer forming step S2, and separation step S3 are repeated in sequence until the ingot 11 is separated (n-1) times.

[0081] Then, when the ingot 11 has been separated (n-1) times (step S4: YES), the ingot 11 and the wafer 23 are ground until each has a finishing thickness T1, thereby removing the remaining separation layer (i.e., the remaining separation layer on the ingot side or the remaining separation layer on the wafer side) and flattening the ingot and the wafer (two wafers) (final flattening step S6).

[0082] The thickness of ingot 11 at the time when the series of steps including separation layer formation step S2, separation step S3, and final flattening step S6 is started (i.e., at the time when the last separation layer formation step S2 is started) corresponds to the thickness obtained by doubling the finishing thickness T1 of wafer 23, plus the estimated thickness T2 of separation layer 21, and the distributed thickness ΔT of ingot 11.

[0083] In addition, the thickness of the ingot 11 at the start of the final flattening step S6 is greater than or equal to the minimum thickness of the ingot 11 required to manufacture the final wafer 23 (specifically, the thickness obtained by adding the finishing thickness T1 of the wafer 23 and the thickness of the remaining separation layer on the ingot side) and less than or equal to the thickness obtained by adding the minimum thickness of the ingot 11 required to manufacture the final wafer 23 and the distributed thickness ΔT.

[0084] The final planarization step S6 is performed in the same manner as the non-final planarization step S5 described above. Therefore, a detailed description of the final planarization step S6 will be omitted here. Then, when the final planarization step S6 is completed, the manufacturing of n wafers 23 from the ingot 11 is completed. That is, the wafer manufacturing method shown in FIG. 2 is completed.

[0085] In the wafer manufacturing method shown in FIG. 2, in a non-final flattening step S5 included in a series of steps for manufacturing a wafer 23 from an ingot 11, the ingot 11 is ground until the thickness of the ingot 11 at the start of the series of steps is thinner than the thickness of the ingot 11 by a thickness obtained by adding together the finished thickness of the wafer 23, the expected thickness T2 of the separation layer 21, and a distributed thickness ΔT obtained by dividing the excess thickness T3 of the ingot 11 by the number (n-1) obtained by subtracting 1 from the maximum number n of wafers 23 that can be manufactured from the ingot 11.

[0086] Then, by repeating this series of steps, an ingot 11 having a thickness greater than or equal to the minimum thickness of the ingot 11 required to manufacture the final wafer 23 (specifically, the thickness obtained by adding the finishing thickness T1 of the wafer 23 and the thickness of the remaining separation layer on the ingot side) and less than or equal to the thickness obtained by adding the minimum thickness of the ingot 11 required to manufacture the final wafer 23 and the distributed thickness ΔT is subjected to the final flattening step S6.

[0087] In this case, the time required to manufacture the last wafer 23 is shortened by grinding the ingot 11 until the ingot 11 has a finishing thickness T1 of the wafer 23. Therefore, by applying the wafer manufacturing method shown in Fig. 2 as a method for manufacturing an upper limit number n of wafers 23 from each ingot 11 while simultaneously processing a plurality of ingots 11 in parallel, grinding of the ingots 11 for manufacturing the last wafer 23 from each ingot 11 is less likely to become a bottleneck, and the time required can be reduced.

[0088] The above-mentioned content is one aspect of the present invention, and the present invention is not limited to the above-mentioned content. For example, in the present invention, a measurement step for measuring the initial thickness T0 of the ingot 11 may be performed before the calculation step S1.

[0089] In the present invention, an ultrasonic wave applying step may be performed after the separation layer forming step S2 and before the separation step S3, in which ultrasonic waves are applied to the front surface 11a side of the ingot 11. In this case, the cracks 19 included in the separation layer 21 are extended in the ultrasonic wave applying step, making it easier to separate the ingot 11 in the separation step S3.

[0090] The present invention may also be a processing apparatus for manufacturing three or more wafers 23 from an ingot 11. Fig. 8 is a block diagram showing a schematic example of such a processing apparatus. The processing apparatus 40 shown in Fig. 8 includes a laser processing unit 42, a separating unit 44, a flattening unit 46, and a controller 48.

[0091] The laser processing unit 42 has a structure similar to that of the laser processing device 2 shown in Fig. 4. Therefore, in the laser processing unit 42, it is possible to form the separation layer 21 inside the ingot 11 as described above.

[0092] The separating unit 44 has a structure similar to that of the separating apparatus 14 shown in Fig. 6. Therefore, in the separating unit 44, it is possible to separate the ingot 11 at the separating layer 21 to produce the wafers 23 as described above.

[0093] The planarization unit 46 has a structure similar to that of the grinding device 24 shown in Fig. 7. Therefore, in the planarization unit 46, as described above, it is possible to remove the ingot-side remaining separation layer remaining on the ingot 11 and the wafer-side remaining separation layer remaining on the wafer 23, thereby planarizing each of the ingot 11 and the wafer 23.

[0094] In addition, in the planarization unit 46, only planarization of the ingot 11 may be performed. In this case, a planarization unit other than the planarization unit 46 may be provided in the processing apparatus 40, and the planarization of the wafer 23 may be performed in the planarization unit. Alternatively, in this case, the planarization of the wafer 23 may be performed in an apparatus (e.g., a grinding apparatus) other than the processing apparatus 40.

[0095] The controller 48 has a processor 50 and a memory 52. ​​The processor 50 is configured, for example, by a CPU (Central Processing Unit) etc. The memory 52 is configured, for example, by a volatile memory such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory) and a non-volatile memory such as an SSD (Solid State Drive) (NAND type flash memory) or an HDD (Hard Disk Drive) (magnetic storage device).

[0096] The memory 52 stores data, programs, and the like used in the processor 50. Examples of this data include the initial thickness T0 of the ingot 11, the finished thickness T1 of the wafer 23, the estimated thickness T2 of the separation layer 21, the thickness of the remaining separation layer on the ingot side, and the thickness of the remaining separation layer on the wafer side. Examples of this program include a program for carrying out the wafer manufacturing method shown in FIG. 2 in the processing apparatus 40.

[0097] The processor 50 reads out and executes a program stored in the memory 52 while utilizing the data stored in the memory 52. ​​For example, the processor 50 refers to the initial thickness T0 of the ingot 11 stored in the memory 52, and reads out from the memory 52 a program for implementing the wafer manufacturing method shown in FIG.

[0098] Specifically, when the wafer manufacturing method shown in FIG. 2 is performed in the processing apparatus 40, the processor 50 first calculates the upper limit number n of wafers that can be manufactured from the ingot 11 and the excess thickness T3 of the ingot 11 by referring to the initial thickness T0 of the ingot 11, the finished thickness T1 of the wafer 23, and the assumed thickness T2 of the separation layer 21 stored in the memory 52 (calculation step S1).

[0099] Then, the processor 50 stores the calculated upper limit number n of wafers that can be manufactured from the ingot 11 and the surplus thickness T3 of the ingot 11 in the memory 52. ​​Furthermore, the processor 50 may calculate the distributed thickness ΔT of the ingot 11 by referring to the upper limit number n of wafers that can be manufactured from the ingot 11 and the surplus thickness T3 of the ingot 11, and store this in the memory 52.

[0100] Once calculation step S1 is completed, processor 50 controls laser processing unit 42, separation unit 44 and planarization unit 46 to repeat a series of steps including formation of separation layer 21 (separation layer formation step S2), separation of ingot 11 (separation step S3), and planarization of ingot 11 (non-final planarization step S5 or final planarization step S6) a number of times (n-1) obtained by subtracting 1 from the maximum number n of wafers 23 that can be produced from ingot 11.

[0101] In addition, in the processing device of the present invention, all processing units (specifically, the laser processing unit, the separating unit, and the flattening unit) are not controlled by one controller, but a controller may be provided for each processing unit, and each processing unit may be controlled by a separate controller. Fig. 9 is a block diagram showing a schematic example of a processing device in which a controller is provided for each processing unit.

[0102] 9 includes a laser processing unit 56 having a sub-controller 56a, a separation unit 58 having a sub-controller 58a, a flattening unit 60 having a sub-controller 60a, and a main controller 62. In other words, the processing device 54 has a similar structure to the processing device 40 shown in FIG. 8, except that the controller 48 is distributed as the sub-controllers 56a, 58a, 60a, and the main controller 62.

[0103] The laser processing unit 56 has, for example, a sub-controller 56a including a processor and a memory, in addition to the same components as those of the laser processing device 2 shown in Fig. 4. This memory stores, for example, data and programs required for forming the separation layer 21 in the laser processing unit 56 (separation layer forming step S2).

[0104] The separating unit 58 has, for example, a sub-controller 58a including a processor and a memory in addition to components similar to those of the separating apparatus 14 shown in Fig. 6. The memory stores, for example, data and programs required for separating the ingot 11 in the separating unit 58 (separating step S3).

[0105] The planarizing unit 60 has, for example, a sub-controller 60a including a processor and a memory in addition to components similar to those of the grinding device 24 shown in Fig. 7. The memory stores, for example, data and programs required for planarizing the ingot 11 and the wafer 23 in the planarizing unit 60 (non-final planarizing step S5 and final planarizing step S6).

[0106] In addition, in the planarization unit 60, only planarization of the ingot 11 may be performed. In this case, a planarization unit other than the planarization unit 60 may be provided in the processing device 54, and the wafer 23 may be planarized in the planarization unit. Alternatively, in this case, the wafer 23 may be planarized in a device (e.g., a grinding device) other than the processing device 54.

[0107] The main controller 62 includes a processor and a memory. In addition, the memory stores in advance, for example, the initial thickness T0 of the ingot 11, the finished thickness T1 of the wafer 23, the estimated thickness T2 of the separation layer 21, the thickness of the ingot-side remaining separation layer, and the thickness of the wafer-side remaining separation layer. The main controller 62 is also connected to the sub-controllers 56a, 58a, and 60a via wired or wireless communication lines.

[0108] In the processing device 54, a calculation step S1 is performed by the main controller 62. Specifically, with reference to the initial thickness T0 of the ingot 11, the finished thickness T1 of the wafer 23, and the estimated thickness T2 of the separation layer 21 stored in the memory of the main controller 62, a processor of the main controller 62 calculates the upper limit number n of wafers that can be manufactured from the ingot 11 and the excess thickness T3 of the ingot 11.

[0109] Then, the processor of the main controller 62 transmits data required to specify the above-mentioned predetermined depth (i.e., the distance between the focal point of the laser beam irradiated onto the ingot 11 in the separation layer forming step S2 and the surface 11a of the ingot 11) to the sub-controller 56a. Note that this data includes, for example, the finished thickness T1 of the wafer, the thickness of the wafer-side remaining separation layer, and data required to calculate the distributed thickness ΔT of the ingot 11 (specifically, the upper limit number n of wafers that can be manufactured from the ingot 11 and the excess thickness T3 of the ingot 11).

[0110] The processor of the main controller 62 also transmits data required to specify the above-mentioned predetermined thickness to the sub-controller 60a. This data includes, for example, the finished thickness T1 of the wafer 23, the estimated thickness T2 of the separation layer 21, and data required to calculate the distributed thickness ΔT of the ingot 11.

[0111] The processor of the main controller 62 may calculate the distributed thickness ΔT of the ingot 11 in addition to the upper limit number n of wafers that can be produced from the ingot 11 and the surplus thickness T3 of the ingot 11. In this case, the processor of the main controller 62 may transmit the distributed thickness ΔT of the ingot 11 itself to the sub-controllers 56a, 60a in place of data required for calculating the distributed thickness ΔT of the ingot 11.

[0112] When the calculation step S1 in the main controller 62 is completed, the main controller 62 transmits a signal to the sub-controller 56a to command the formation of the separation layer 21 (separation layer forming step S2) in the laser processing unit 56. Then, when the separation layer forming step S2 is completed by the sub-controller 56a controlling the same components as those of the laser processing device 2 shown in FIG.

[0113] When the main controller 62 receives the signal from the sub-controller 56a, the main controller 62 transmits a signal to the sub-controller 58a instructing the sub-controller 58a to separate the ingot 11 (separation step S3) in the separation section 58. Then, when the separation step S3 is completed by the sub-controller 58a controlling components similar to those of the separation device 14 shown in FIG. 6, the sub-controller 58a transmits a signal to that effect to the main controller 62.

[0114] When the main controller 62 receives the signal from the sub-controller 58a, the main controller 62 transmits a signal to the sub-controller 60a instructing the sub-controller 60a to perform flattening of the ingot 11 (non-final flattening step S5) in the flattening unit 60. Then, when the non-final flattening step S5 is completed by the sub-controller 60a controlling components similar to those of the grinding device 24 shown in FIG. 7, the sub-controller 60a transmits a signal to that effect to the main controller 62.

[0115] Furthermore, the exchange of signals between the sub-controllers 56a, 58a, 60a and the main controller 62 is repeated until the main controller 62 receives signals from the sub-controller 58a indicating that the separation step S3 has been completed a number (n-1) obtained by subtracting 1 from the maximum number n of wafers 23 that can be produced from an ingot 11.

[0116] Then, when the main controller 62 receives the number (n-1) of signals from the sub-controller 58a, the main controller 62 transmits a signal to instruct the sub-controller 60a to perform flattening of the ingot 11 (final flattening step S6) in the flattening unit 60. Then, when the final flattening step S6 is completed by the sub-controller 60a controlling components similar to those of the grinding device 24 shown in FIG. 7, the sub-controller 60a transmits a signal to that effect to the main controller 62.

[0117] In addition, the above-mentioned processing apparatus 40, 54 may be provided with additional components. For example, the processing apparatus 40, 54 may be provided with a measurement unit for measuring the initial thickness T0 of the ingot 11. The processing apparatus 40, 54 may also be provided with a transport unit for transporting the ingot 11 to or from any of the laser processing units 42, 56, the separation units 44, 58, and the flattening units 46, 60.

[0118] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0119] 2: Laser processing equipment 4: Chuck table 6: Laser beam irradiation unit 8: Head 10: Housing 11: Ingot (11a: front surface, 11b: back surface) (11c: c-axis, 11d: perpendicular, 11e: c-plane) 12: Imaging unit 13: Primary orientation flat 14: Separation device 15: Secondary orientation flat 16: Chuck table 17: Modification section 18: Separation unit 19: Crack 20: Suction plate 21: Separation layer 22: Vertical movement mechanism 23: Wafer (23a: one side) 24: Grinding equipment 26: Chuck table 28: Grinding unit 30: Spindle 32: Mount 34: Grinding wheel 36: Foundation 38: Grinding wheel 40: Processing equipment 42: Laser processing section 44: Separation part 46: Flattening part 48: Controller 50: Processor 52: Memory 54: Processing equipment 56: Laser processing section (56a: Sub-controller) 58: Separation unit (58a: sub-controller) 60: Flattening unit (60a: Sub-controller) 62: Main controller

Claims

1. A method for manufacturing a wafer, comprising: a separation layer forming step for forming a separation layer inside an ingot; a separation step for manufacturing wafers by separating the ingot at the separation layer after the separation layer forming step; and a planarization step for removing an ingot-side remaining separation layer remaining in the ingot and a wafer-side remaining separation layer remaining in the wafer after the separation step, thereby planarizing the ingot and the wafer, A calculation step of calculating an upper limit number of the wafers that can be produced from the ingot and an excess thickness of the ingot, with reference to an initial thickness of the ingot, a finished thickness of the wafer, and an expected thickness of the separation layer, prior to the production of three or more wafers from the ingot; In the separation layer forming step, the separation layer is formed by relatively moving the ingot and the focal point of the laser beam having a wavelength that transmits through the material of the ingot while irradiating the ingot with the laser beam so that the focal point is positioned at a predetermined depth from the surface of the ingot, In the planarization step, The ingot is ground until the thickness of the ingot is thinner than the thickness of the ingot at the start of the series of steps by a thickness obtained by adding the finishing thickness, the expected thickness, and a distributed thickness obtained by dividing the excess thickness by a number obtained by subtracting 1 from the upper limit number, and The method of manufacturing a wafer wherein the wafer is ground to the finish thickness.

2. 2. The method for producing a wafer according to claim 1, wherein the predetermined depth corresponds to a first thickness obtained by adding the finishing thickness and a thickness of the wafer-side remaining separation layer.

3. 2. The method for producing a wafer according to claim 1, wherein the predetermined depth corresponds to a second thickness obtained by adding the finishing thickness, the thickness of the wafer-side remaining separation layer, and the distributed thickness.

4. 2. The method for manufacturing a wafer according to claim 1, wherein the predetermined depth is longer than a first thickness obtained by adding the finishing thickness and the thickness of the wafer-side remaining separation layer, and shorter than a second thickness obtained by adding the first thickness and the distributed thickness.

5. A processing apparatus for manufacturing three or more wafers from an ingot, a laser processing unit for forming a separation layer inside the ingot; a separating section for producing the wafer by separating the ingot at the separating layer; a planarizing unit for removing the ingot-side remaining separation layer remaining on the ingot to planarize the ingot; a controller for controlling the laser processing unit, the separating unit, and the planarizing unit so as to repeat a series of steps including the formation of the separation layer, the separation of the ingot, and the planarization of the ingot a number of times obtained by subtracting 1 from the upper limit number of the wafers that can be manufactured from the ingot; The controller a memory for storing the initial thickness of the ingot, the finished thickness of the wafer, and the assumed thickness of the separation layer; A processor for calculating the upper limit number and the excess thickness of the ingot by referring to the initial thickness, the finished thickness, and the estimated thickness, The processor The laser processing unit is controlled so that the separation layer is formed by relatively moving the ingot and the focal point of the laser beam having a wavelength that transmits through the material of the ingot, while irradiating the ingot with the laser beam so that the focal point is positioned at a predetermined depth from the surface of the ingot, and A processing apparatus that controls the flattening unit so that the ingot is ground until the thickness thereof is thinner than the thickness of the ingot at the start of the series of steps by the sum of the finishing thickness, the expected thickness, and a distributed thickness obtained by dividing the excess thickness by a number obtained by subtracting 1 from the upper limit number.

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