Wafer circular cutting method

Abstract

To provide a wafer annular cutting method of forming a beveled part to an outer peripheral edge of a wafer when generating a wafer with a small diameter by cutting a wafer with a large diameter in an annular shape.SOLUTION: A method includes the steps of: holding one surface of a wafer W to a chuck table and exposing the other surface Wa; positioning a cutting blade 83 at a desired radial diameter which is smaller than the radial diameter of the wafer from a rotational center of the wafer; forming an annular groove 100-1 by cutting, by the cutting blade, the wafer from the other surface by a predetermined first depth; forming new annular grooves 101-2 and 101-3 by cutting, by the cutting blade, the wafer so as to be deeper than the cutting depth obtained by previously cutting from the other surface while moving the cutting blade to an outer side of a radial direction of the wafer until the depth of the annular groove from the other surface reaches the half of the thickness of the wafer; reversing the wafer when the depth of the annular groove reaches the half of the thickness of the wafer; holding the other surface to the chuck table and exposing one surface; and repeatedly forming wafer the similar annular groove to the one surface of the wafer.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a wafer annular cutting method for annularly cutting a wafer. [Background technology]

[0002] A wafer with multiple devices such as ICs and LSIs formed on its surface and divided by planned dividing lines has its back surface ground using a grinding machine to form it to the desired thickness, and then is divided into individual device chips using a dicing machine and laser processing machine, and these are used in electrical devices such as mobile phones and personal computers.

[0003] The diameter of the wafer varies widely, for example, φ100 mm, φ150 mm, φ200 mm, and φ300 mm, and is appropriately selected in consideration of production efficiency when forming a plurality of devices on the surface of the wafer.

[0004] When examining various processing conditions such as wafer grinding conditions, cutting conditions, laser processing conditions, and transport conditions, so-called dummy wafers, which have no devices formed on their surface, are generally used. Dummy wafers can be obtained by cutting a large-diameter wafer into an annular shape as needed to produce a wafer of the desired small diameter, and the present application proposes a method for cutting a wafer into an annular shape (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-54461 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, wafers on which devices are actually formed and which are then divided into individual device chips may have chamfered portions formed by removing corners from the outer peripheral edge. In contrast, when a small-diameter dummy wafer is formed using the technology described in Patent Document 1, such chamfered portions are not formed on the outer peripheral edge of the wafer, which poses a problem that it is not possible to set highly accurate processing conditions when considering the various processing conditions described above.

[0007] In particular, in the case of wafers formed from a material with high hardness, such as SiC wafers and sapphire wafers, there is a problem in that it is difficult to perform chamfering on the outer peripheral edge of the wafer after the wafer has been processed into an annular shape.

[0008] The present invention has been made in consideration of the above-mentioned facts, and its main technical object is to provide a wafer annular cutting method that can form a chamfered portion on the outer peripheral edge of a wafer when cutting a large-diameter wafer into an annular shape to produce a small-diameter wafer. [Means for solving the problem]

[0009] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a wafer annular cutting method for annularly cutting a wafer, comprising: a one-side surface holding step of holding one side of the wafer on a rotatable chuck table constituting a cutting device and exposing the other side; a cutting blade positioning step of positioning a cutting blade at a desired radius from the center of rotation of the wafer held on the chuck table that is smaller than the radius of the wafer; a first annular groove forming step of cutting the cutting blade from the other side to a predetermined first depth to form an annular groove; a second annular groove forming step of moving the cutting blade a predetermined first distance outward in the radial direction of the wafer and cutting from the other side to a second depth deeper than the first depth to form an annular groove; and a third annular groove forming step of moving the cutting blade a predetermined second distance outward in the radial direction of the wafer and cutting from the other side to a third depth deeper than the second depth to form an annular groove, and after the third annular groove forming step, a second annular groove forming step of repeatedly forming a new annular groove by moving the cutting blade radially outward of the wafer and cutting from the other surface deeper than the depth of the previous cut until the depth of the annular groove from that surface reaches half the thickness of the wafer, and then a second annular groove forming step of holding the other surface of the wafer on a chuck table to expose one surface is performed, the cutting blade is positioned at the desired radius from the center of rotation of the wafer, and the above-mentioned first annular groove forming step, second annular groove forming step, and third annular groove forming step are performed on one surface of the wafer, and after the third annular groove forming step, a one-surface annular groove forming step is performed in which the cutting blade is moved radially outward of the wafer and cutting from that one surface deeper than the depth of the previous cut until the depth of the annular groove from the exposed one surface reaches half the thickness of the wafer.

[0010] Preferably, the method further includes, before the other surface holding step, a step of positioning the wafer in an opening of a frame having an opening large enough to accommodate the wafer, and pressing a tape between the other surface of the wafer and the frame to integrate the wafer and the frame via the tape. Furthermore, to continuously perform the first annular groove forming step, the second annular groove forming step, the third annular groove forming step, and subsequent annular groove forming steps, a cutting blade may be moved radially outward at a predetermined speed as the chuck table rotates, and also moved at a predetermined speed in the cutting feed direction to spirally cut the wafer to form the annular groove. Furthermore, the wafer may be made of either SiC or sapphire. [Effects of the Invention]

[0011] The wafer annular cutting method of the present invention includes a one-side surface holding step of holding one side of a wafer on a rotatable chuck table constituting a cutting device and exposing the other side; a cutting blade positioning step of positioning a cutting blade at a desired radius smaller than the radius of the wafer from the center of rotation of the wafer held on the chuck table; a first annular groove forming step of cutting the cutting blade from the other side to a predetermined first depth to form an annular groove; and a first annular groove forming step of moving the cutting blade radially outward of the wafer by a predetermined first distance. a second annular groove forming step of cutting from the other surface to a second depth deeper than the first depth to form an annular groove; and a third annular groove forming step of moving the cutting blade a predetermined second distance outward in the radial direction of the wafer and cutting from the other surface to a third depth deeper than the second depth to form an annular groove, and after the third annular groove forming step, the cutting blade is moved radially outward of the wafer and cut from the other surface to a third depth deeper than the second depth until the depth of the annular groove from the other surface reaches half the thickness of the wafer. An other-side annular groove forming step is carried out in which new annular grooves are repeatedly formed by cutting deeper than the cut depth, and then an other-side surface holding step is carried out in which the other side of the wafer is held on a chuck table to expose one side, and the cutting blade is positioned at the desired radius from the center of rotation of the wafer, and the above-mentioned first annular groove forming step, second annular groove forming step, and third annular groove forming step are carried out on one side of the wafer, and after the third annular groove forming step, a new annular groove is repeatedly formed on the exposed one side. A one-side annular groove forming process is performed in which the cutting blade is moved radially outward of the wafer and a new annular groove is repeatedly formed by cutting deeper from one side than the previous cut until the depth of the annular groove reaches half the thickness of the wafer.This makes it possible to cut a large-diameter wafer into an annular shape and form a small-diameter wafer, not only for wafers made of silicon (Si) but also for wafers made of hard materials such as SiC and sapphire, and also makes it easy to form a chamfered portion at the outer peripheral edge. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an overall perspective view of a cutting device suitable for this embodiment. [Figure 2] 1A is a perspective view showing an embodiment of a step of holding one surface, and FIG. 1B is a perspective view showing an embodiment of a step of forming an annular groove on the other surface. [Figure 3] 3 is a partially enlarged cross-sectional view showing how the dummy wafer is cut in the first to third annular groove forming steps shown in FIG. 2. FIG. [Figure 4] FIG. 10 is a perspective view showing an embodiment of an integration step for integrating a dummy wafer and a frame. [Figure 5] FIG. 10 is a perspective view showing a mode in which one surface of the dummy wafer is turned upside down. [Figure 6] FIG. 10 is a perspective view showing an embodiment of a step of forming an annular groove on one surface. [Figure 7] FIG. 10 is a partially enlarged cross-sectional view showing a state in which a small-diameter dummy wafer has been separated. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a wafer annular cutting method according to the present invention will be described in detail with reference to the accompanying drawings.

[0014] 1 shows an overall perspective view of a cutting apparatus 1 suitable for carrying out the wafer annular cutting method of this embodiment. The workpiece to be processed by the cutting apparatus 1 is a large-diameter dummy wafer W made of, for example, SiC, having a thickness of 750 μm and a diameter of φ200 mm, with no devices formed on the front or back surface. By the wafer annular cutting method of this embodiment, which will be described below, the large-diameter dummy wafer W is annularly cut to produce a small-diameter dummy wafer Wd having a diameter of φ150 mm.

[0015] The cutting device 1 includes a housing 2 having a substantially rectangular parallelepiped shape, a cassette 4 placed on a cassette table 4a of the housing 2, a carry-in / out means 3 for carrying a dummy wafer W from the cassette 4 to a temporary storage table 5, a transport means 6 having a swivel arm for transporting the dummy wafer W carried out to the temporary storage table 5 to a rotatable chuck table 22 of a holding means 20, a cutting means 8 for cutting the dummy wafer W held on the chuck table 22, an alignment means 10 for imaging the dummy wafer W held on the chuck table 22 and detecting the center of rotation of the dummy wafer W and the cutting position by the cutting means 8, and a cleaning / carry-out means 14 for transporting the dummy wafer W from the carry-in / out position where the chuck table 22 is positioned in FIG. 1 to a cleaning device 12 (details are omitted). The cutting device 1 is further provided with a control means, a display means, etc. (not shown). As shown in Fig. 2(a), the chuck table 22 includes a frame 22a and a suction chuck 22b formed of a breathable material and surrounded by the frame 22a. A suction source (not shown) is connected to the suction chuck 22b, and when the suction source is activated, a negative pressure is generated on the holding surface formed by the suction chuck 22b. Note that clamps and the like disposed on the outer periphery of the chuck table 22 are omitted as appropriate in Figs. 2(a) and 2(b).

[0016] When carrying out the wafer annular cutting method of this embodiment, as shown in FIG. 2(a), one side Wb of the dummy wafer W is placed on the chuck table 22 constituting the cutting device 1 and held by suction, and a one-side surface holding step is carried out in which the other side Wa is exposed upward.

[0017] Next, a cutting blade positioning step is carried out in which the cutting blade is positioned at a desired radius that is smaller than the radius of the dummy wafer W from the center of rotation of the dummy wafer W held on the chuck table 22. More specifically, the chuck table 22 is moved in the X-axis direction indicated by the arrow X in Fig. 1 by operating an X-axis moving means (not shown), and positioned below the above-mentioned alignment means 10. An image of the dummy wafer W is then taken, and the center of rotation O of the dummy wafer W shown in Fig. 2(b) and the cutting position Wr (indicated by a two-dot chain line) are detected.

[0018] The cutting means 8 includes a spindle 82 disposed in the Y-axis direction indicated by the arrow Y in FIG. 1 and rotatably held in a spindle housing 81, a cutting blade 83 held at the tip of the spindle 82, a blade housing 84 covering the cutting blade 83, and a cutting water supply nozzle 85 to which cutting water is supplied via the blade housing 84. The cutting means 8 also includes a Y-axis moving means (not shown) for moving the cutting blade 83 in the Y-axis direction. The spindle 82 is rotationally driven by a spindle motor (not shown), causing the cutting blade 83 to rotate in the direction indicated by the arrow R1. The cutting blade 83 in this embodiment has, for example, a diameter of φ50 mm and a thickness of 30 μm.

[0019] In this embodiment, the cutting position Wr is a desired radius smaller than the radius (100 mm) of the dummy wafer W, for example, a position 75 mm in the radial direction from the rotation center O of the dummy wafer W. Once the rotation center O and the cutting position Wr have been detected by the alignment means 10, the X-axis moving means and Y-axis moving means described above are operated to position the cutting blade 83 of the cutting means 8 at the cutting position Wr of the dummy wafer W, thereby completing the cutting blade positioning step.

[0020] After the cutting blade positioning process described above has been carried out, the other surface annular groove forming process is carried out, which includes at least the first annular groove forming process, the second annular groove forming process, and the third annular groove forming process described below.

[0021] The first annular groove forming step is a step of cutting the above-mentioned cutting blade 83 into the exposed other surface Wa of the dummy wafer W to a first depth to form an annular groove, and more specifically, is carried out as follows.

[0022] As shown in FIG. 2(b), the cutting blade 83 of the cutting means 8 is positioned over the cutting position Wr of the dummy wafer W while rotating in the direction indicated by arrow R1, and the chuck table 22 is rotated in the direction indicated by arrow R2 while cutting a predetermined first depth ΔZ (e.g., 15 μm) from the other surface Wa of the dummy wafer W, as shown in FIG. 3(a). The rotation speed of the chuck table 22 is, for example, 15 degrees / second, and the time t required for one rotation is 24 seconds. As a result, an annular groove 100 (indicated by 100-1 in FIG. 3(a)) is formed along the cutting position Wr indicated by the two-dot chain line in FIG. 2(b), completing the first annular groove forming process. The second annular groove forming process, which is performed after the first annular groove forming process, is performed, for example, as follows.

[0023] When performing the second annular groove forming process, the cutting blade 83 is raised and moved radially outward from the position where the annular groove 100-1 was formed on the dummy wafer W by a predetermined first distance Δr1 (e.g., 12 μm). While rotating the chuck table 22 in the direction indicated by arrow R2 at the rotational speed described above, the cutting blade 83 cuts into the other surface Wa of the dummy wafer W from above to a second depth (e.g., 30 μm) that is deeper than the first depth ΔZ by ΔZ, as shown in FIG. 3(b). This forms annular groove 100-2 adjacent to and outside of the previously formed annular groove 100-1. Because the first distance Δr1 is set to a value smaller than the thickness (30 μm) of the cutting blade 83, the annular grooves 100-1 and 100-2 are continuously formed in a stepped shape. Furthermore, a third annular groove forming process, which is performed after the second annular groove forming process is completed, is performed, for example, as follows.

[0024] When performing the third annular groove forming step, the cutting blade 83 is raised and moved radially outward from the position where the annular groove 100-2 was formed on the dummy wafer W by a predetermined second distance Δr2 (e.g., 12 μm), and while rotating the chuck table 22 in the direction indicated by arrow R2, the cutting blade 83 cuts into the other surface Wa of the dummy wafer W from above to a third depth (e.g., 45 μm) that is deeper than the second depth (30 μm) by ΔZ, as shown in FIG. 3(c), to form annular groove 100-3 adjacent to and outside the previously formed annular groove 100-2. Since the second distance Δr2 is also set to a value smaller than the thickness dimension (30 μm) of the cutting blade 83, the annular grooves 100-2 and 100-3 are continuous and formed in a substantially stepped shape. Once the third annular groove forming step is completed in this manner, the fourth annular groove forming step, the fifth annular groove forming step, ..., the nth annular groove forming step are carried out while repeating the same processing procedure as the first to third annular groove forming steps described above until the annular grooves reach half the thickness (375 μm) of the dummy wafer W, thereby forming the annular grooves 100-4 to 100-n. Once the annular groove 100-n reaches half the thickness of the dummy wafer W, the other surface annular groove forming step is completed. Note that the actual values of ΔZ and Δr described above are set arbitrarily and are determined based on the desired chamfer shape.

[0025] Next, an other-surface holding step is performed in which the other surface Wa of the dummy wafer W is held on the chuck table 22 to expose one surface Wb. More specifically, first, as shown in Fig. 4, a dummy wafer W having an annular groove 100 (100-1 to 100-n) formed therein by the other-surface annular groove forming step described above, an annular frame F having an opening Fa capable of accommodating the dummy wafer W, and tape T having adhesive properties on its surface are prepared. Next, an integration step is performed in which the back surface of the frame F faces upward, the other surface Wa of the dummy wafer W faces upward and is positioned in the center of the opening Fa, and the tape T is pressure-bonded to the other surface Wa of the dummy wafer W and the frame F to integrate them (see the upper part of Fig. 5).

[0026] Next, as shown in the lower part of Fig. 5, the frame F integrated with the dummy wafer W via the tape T is inverted. As a result, one surface Wb of the dummy wafer W on which the annular groove 100 is not formed faces upward. The other surface Wa of the dummy wafer W thus integrated by being held on the frame F is held on the chuck table 22 of the cutting device 1 described with reference to Fig. 1, and one surface Wb is exposed upward, completing the other surface holding step.

[0027] After the other surface holding step has been performed as described above, the above-described alignment means 10 is used to detect the rotation center O of the dummy wafer W and the cutting position Wr on one surface Wb set 75 mm outward from the rotation center. Next, as shown in FIG. 6, the cutting blade 83 of the cutting means 8 is positioned at the cutting position Wr. Then, while rotating the cutting blade 83 in the direction indicated by arrow R3 and rotating the dummy wafer W together with the above-described chuck table 22 in the direction indicated by arrow R4, the above-described first annular groove forming step, second annular groove forming step, and third annular groove forming step are performed on one surface Wb of the dummy wafer W. Next, after this third annular groove forming step, the cutting blade 83 is repeatedly moved radially outward of the dummy wafer W and cuts deeper from the exposed surface than the previous cut depth to form the annular groove 110, until the depth of the annular groove from the exposed one surface Wb reaches half the thickness of the dummy wafer W. Note that this one surface annular groove forming step is the same procedure as the above-mentioned other surface annular groove forming step, so a detailed description thereof will be omitted.

[0028] By performing the other-surface annular groove forming step and one-surface annular groove forming step described above, the annular groove 100 and the annular groove 110 are connected, and as shown in FIG. 7(a), the outer peripheral region Wc is separated from the large-diameter dummy wafer W having a diameter of 200 mm, thereby obtaining a small-diameter dummy wafer Wd having a diameter of approximately 150 mm. Then, as shown in FIG. 7(b), a minute step-like chamfered portion We is formed at the outer peripheral edge of the small-diameter dummy wafer Wd by the other-surface annular groove forming step and one-surface annular groove forming step described above. Note that FIG. 7(b) is a simplified view of the chamfered portion We for convenience of explanation, and does not represent the actual number of steps.

[0029] In the above embodiment, an example is shown in which a dummy wafer W having no devices or the like formed on its surface is cut into a ring shape, but the present invention is not limited to this, and may also be performed on a wafer having a plurality of devices formed on its surface, separated by planned dividing lines.

[0030] According to the above-described embodiment, even if the wafer is made of a hard material such as not only silicon (Si) but also SiC or sapphire, it is possible to form a small diameter wafer by cutting a large diameter wafer into an annular shape, and it is also possible to easily form a chamfered portion at the outer peripheral end.

[0031] In the above-described embodiment, the first annular groove forming step, the second annular groove forming step, the third annular groove forming step, and the subsequent other-surface annular groove forming step or one-surface annular groove forming step (hereinafter referred to as "annular groove forming step") are carried out stepwise on one surface Wb and the other surface Wa of the dummy wafer W, so that the chamfered portion We is formed in a stepped shape. However, the present invention is not limited to this, and the above-described first annular groove forming step, second annular groove forming step, third annular groove forming step, and subsequent steps may be carried out step by step. In order to continuously perform the annular groove forming process, the cutting blade 83 may be moved radially outward at a predetermined speed (for example, Δr μm / t seconds, where t seconds is the time it takes for the chuck table 22 to rotate) as the chuck table 22 rotates, and the cutting depth may be increased at a predetermined speed in the cutting feed direction (for example, ΔZ μm / t seconds, where t seconds is the time it takes for the chuck table 22 to rotate once), thereby cutting in a spiral shape to form the above-mentioned annular grooves 100, 110.

[0032] In the above embodiment, the cutting depth of the cutting blade 83 is gradually increased by a fixed depth (ΔZ=15 μm) when performing the first annular groove forming step, the second annular groove forming step, the third annular groove forming step, and the subsequent annular groove forming steps. However, the present invention is not limited to this, and the amount of change in the cutting depth may be gradually changed. Similarly, when moving the cutting blade 83 radially outward of the wafer, the cutting blade 83 is moved in steps by a fixed distance (Δr=12 μm). However, the present invention is not limited to this, and the distance moved radially outward of the wafer may be gradually changed.

[0033] In the above embodiment, the cross-sectional shape of the tip of the cutting blade 83 is set to be approximately rectangular as shown in Fig. 3, but the present invention is not limited to this, and it is also possible to use a cutting blade whose cross-sectional shape of the tip is V-shaped to match the chamfered shape of the outer peripheral edge of a small-diameter wafer. However, since the V-shape of the tip of the cutting blade is subject to deformation due to wear, the tip of the cutting blade needs to be frequently trimmed, which is poor in productivity. Therefore, the cutting blade 83 used in the above embodiment is preferable. [Explanation of symbols]

[0034] 1:Cutting device 2: Housing 3: Carrying in / out means 4: Cassette 5: Temporary table 6: Means of transport 8:Cutting means 81: Spindle housing 82: Spindle 83: Cutting blade 84: Blade housing 85: Cutting water supply nozzle 10: Alignment means 12: Cleaning equipment 14: Cleaning and carrying out means 20: Holding means 22: Chuck table 100, 110: Annular groove W: dummy wafer Wa: The other side Wb: One side Wc: Outer area Wd: small diameter dummy wafer We: Chamfered part Wr: Position to be cut

Claims

1. A wafer annular cutting method for annularly cutting a wafer, comprising: a one-surface holding step of holding one surface of the wafer on a rotatable chuck table constituting a cutting device and exposing the other surface; a cutting blade positioning step of positioning the cutting blade at a desired radius from the center of rotation of the wafer held on the chuck table that is smaller than the radius of the wafer; a first annular groove forming step of cutting the cutting blade from the other surface to a predetermined first depth to form an annular groove; a second annular groove forming step of moving the cutting blade a predetermined first distance radially outward from the wafer and cutting from the other surface to a second depth deeper than the first depth to form an annular groove; and a third annular groove forming step of moving the cutting blade a predetermined second distance radially outward from the wafer and cutting from the other surface to a third depth deeper than the second depth to form an annular groove, and after the third annular groove forming step, a second annular groove forming step is carried out in which the cutting blade is moved radially outward from the wafer and cutting from the other surface deeper than the depth of the previous cut until the depth of the annular groove from the other surface reaches half the thickness of the wafer, Next, an other-side surface holding step is carried out in which the other side of the wafer is held on a chuck table to expose one side, a cutting blade is positioned at the desired radius from the center of rotation of the wafer, and the above-mentioned first annular groove forming step, second annular groove forming step, and third annular groove forming step are carried out on one side of the wafer, and after the third annular groove forming step, a one-side surface annular groove forming step is carried out in which the cutting blade is moved radially outward of the wafer and cuts deeper from the one side of the wafer until the depth of the annular groove from the exposed one side reaches half the thickness of the wafer, repeatedly forming new annular grooves.

2. 2. The wafer annular cutting method according to claim 1, further comprising, before the other surface holding step, a step of positioning the wafer in an opening of a frame having an opening capable of accommodating the wafer, and pressing a tape between the other surface of the wafer and the frame to integrate the wafer and the frame via the tape.

3. 2. The wafer annular cutting method according to claim 1, wherein, in order to continuously perform the first annular groove forming process, the second annular groove forming process, the third annular groove forming process, and subsequent annular groove forming processes, the cutting blade is moved radially outward at a predetermined speed while also moving at a predetermined speed in the cutting feed direction as the chuck table rotates, thereby cutting the wafer in a spiral shape to form the annular groove.

4. 4. The wafer orbital cutting method according to claim 1, wherein the wafer is made of either SiC or sapphire.

Images