A multi-wire sawing method for sapphire wafers

Abstract

The application provides a multi-wire sawing method for sapphire wafers, which comprises the following steps: providing a sapphire crystal bar; the normal line of the cutting surface of the sapphire crystal bar is deflected by a preset deflection angle relative to the optical axis direction towards an initial crystal direction in a basal plane, and the projection direction of the normal line of the cutting surface on the basal plane is parallel to the initial crystal direction; determining the basal plane of the sapphire crystal bar, and recording the projection direction as a first reference crystal direction; taking the first reference crystal direction as a reference, selecting an equivalent crystal direction which is different from the first reference crystal direction by a preset phase difference in the basal plane; taking the first reference crystal direction as a rotation axis, rotating the sapphire crystal bar by the preset phase difference, so that the wire saw feeding direction of a multi-wire sawing machine is along the initial crystal direction; and setting the cutting parameters to carry out sawing, so as to obtain sapphire wafers, and the problem of lateral deviation of the wire saw caused by asymmetric stress is completely eliminated.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor material processing technology, and specifically relates to a multi-wire dicing method for sapphire wafers. Background Technology

[0002] Sapphire (α-Al2O3) substrates are the core material for manufacturing high-end power devices (such as SiC-on-sapphire, GaN HEMT epitaxy, and power LEDs). Therefore, the diced surface often requires specific crystal orientation constraints to match the downstream epitaxial structure. Specifically, the normal to the diced surface must be deflected by a predetermined angle relative to its optical axis (c-axis) towards a certain initial crystal orientation (usually denoted as A0) within the basal plane. For example, C deflected by A 0.8 ± 0.05°, meaning the angle between the diced surface normal and the c-axis is 89.2°, and its projection onto the basal plane is parallel to the A0 direction.

[0003] Currently, existing technologies (such as CN115946253B) typically employ multi-wire cutting processes, directly cutting along the A0 direction as the entry direction. However, during mass production (e.g., 5-inch sapphire ingots), it was discovered that sapphire belongs to the hexagonal crystal system, with six equivalent A-axis distributed along the c-axis projection on its basal plane (0001), spaced 60° apart. The A0 direction used in existing technologies is actually located in the crystal transition region between the c-axis and the adjacent A-axis. In the initial stage of diamond wire saw cutting, the elastic modulus of the sapphire crystals contacted on both sides of the wire saw exhibits a significantly asymmetric distribution (ΔE can reach over 15 GPa). This significant asymmetry directly causes the wire saw to deflect laterally during the cutting process, resulting in an S-shaped (twisted) warp in the cut sapphire wafer. The surface shape indicators such as bow, warp, and total thickness deviation (TTV) are seriously exceeded (e.g., Bow > 15μm, Warp > 50μm, TTV > 15μm).

[0004] Furthermore, due to the severe surface distortion of the wafer, it will cause serious deviations (the deviation value is usually >0.04°) when the crystal orientation is measured by XRD. This makes it impossible for the diced wafer to meet the stringent requirements of surface shape accuracy and crystal orientation accuracy in the subsequent grinding and polishing process of power devices and the device fabrication. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a multi-wire dicing method for sapphire wafers, which solves the technical problems in the prior art.

[0006] On one hand, the invention provides the following technical solution: a multi-wire dicing method for sapphire wafers, the method comprising: A sapphire crystal rod is provided; the normal of the cut surface of the sapphire crystal rod is deflected by a preset deflection angle relative to its optical axis direction toward an initial crystal orientation in a base plane, and the projection direction of the cut surface normal on the base plane is parallel to the initial crystal orientation; the base plane contains a plurality of equivalent crystal orientations that have a crystallographic equivalent relationship with the initial crystal orientation and are periodically distributed with a preset phase difference. The base plane of the sapphire crystal rod is measured, and the projection direction of the normal of the cut surface on the base plane is determined within the base plane, and this projection direction is recorded as the first reference crystal direction; Using the first reference crystal orientation as a reference, an equivalent crystal orientation that differs from the first reference crystal orientation by the preset phase difference is selected in the base plane and used as the cutting crystal orientation. Using the first reference crystal orientation as the rotation axis, the sapphire crystal rod is rotated around the rotation axis by the preset phase difference, so that the wire saw feed direction of the multi-wire cutting machine is along the infeed crystal orientation; Set the cutting parameters and start the multi-wire cutting machine to cut the rotated sapphire ingot to obtain a sapphire wafer.

[0007] Compared to existing technologies, the advantages of this invention are as follows: While strictly maintaining the sapphire crystal rod's spatial tilt angle (i.e., the preset off-cut angle, such as 0.8 ± 0.05°) absolutely unchanged, only the entry azimuth angle is switched from the traditional initial crystal orientation (such as the A0 direction) to an equivalent crystal orientation with a preset phase difference (such as ± 60°) from the initial crystal orientation. This adjustment of the azimuth angle shifts the point of action of the wire saw at the initial cutting stage from the crystal's "crystal orientation transition zone" to the "equivalent crystal orientation symmetry zone" with crystallographic symmetry. Testing has verified that this method can significantly reduce the difference in elastic modulus (ΔE) between the two sides of the diamond wire saw contacting the crystal from over 15 GPa in existing technologies to 5 GPa or less, balancing the cutting resistance on both sides of the wire saw from a physical and mechanical perspective, and completely eliminating the wire bow problem caused by asymmetrical force. Based on this, the wafer surface shape is reconstructed from the S-shaped twist generated in the background technology to a saddle symmetry shape, which significantly improves the surface shape indicators such as warp, total warp, and total thickness deviation (TTV). It also reduces the XRD crystal orientation measurement deviation from >0.04° to <0.01°, ultimately effectively solving the yield loss problem caused by surface distortion in the power device manufacturing process.

[0008] Furthermore, the preset deflection angle is 0.75~0.85°, and the preset phase difference is 55~65°.

[0009] Furthermore, the set cutting parameters include: a diamond wire saw wire diameter of 0.15~0.25 mm, a wire speed of 1200~2400 m / min, a tension of 25~50 N, and a cutting fluid flow rate of 30~80 L / min.

[0010] Furthermore, an equivalent crystal orientation differing from the first reference crystal orientation by +55° to +65° is selected within the base plane as the cutting orientation, and the sapphire crystal rod is rotated by +55° to +65° around the first reference crystal orientation.

[0011] Furthermore, an equivalent crystal orientation that differs from the first reference crystal orientation by -55° to -65° is selected within the base plane as the cutting orientation, and the sapphire crystal rod is rotated by -55° to -65° around the first reference crystal orientation.

[0012] Furthermore, the sapphire crystal obtained after cutting is complete in terms of shape and crystal orientation measurement parameters: warp ≤ 5 μm, total warp ≤ 40 μm, total thickness deviation (TTV) ≤ 10 μm, and XRD crystal orientation measurement deviation < 0.01°.

[0013] Furthermore, the multi-wire cutting machine is a fixed multi-wire cutting machine, and the cutting process does not depend on the oscillating motion of the multi-wire cutting machine.

[0014] Furthermore, the sapphire crystal rod is a 4-inch or 5-inch sapphire crystal rod.

[0015] Furthermore, after performing the above steps to make the wire saw feed direction of the multi-wire cutting machine along the cutter crystal direction, the difference in crystal elastic modulus ΔE on both sides of the diamond wire saw is ≤ 5 GPa.

[0016] Furthermore, the initial crystal orientation is the a-axis crystal orientation, and the equivalent crystal orientation is a crystal orientation in the basal plane that differs from the a-axis crystal orientation by an integer multiple of 60°. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a process flow diagram of the multi-wire dicing method for sapphire wafers according to the present invention.

[0019] Figure 2 This is a schematic diagram of the A-axis distribution and cutting direction within the sapphire substrate of the present invention.

[0020] Figure 3 This is a comparison diagram of the symmetry of the elastic modulus of the crystals on both sides of the diamond wire saw under different cutting directions according to the present invention.

[0021] Figure 4These are comparison images of sapphire wafer surface shapes obtained by cutting under different cutting directions according to the present invention.

[0022] Figure 5 This is a bar chart comparing the warp, total warp, and total thickness deviation (TTV) data of the wafer after dicing according to the present invention.

[0023] Figure 6 This is a scatter plot comparing the crystal orientation measurement error of this invention with the variation of warp shape.

[0024] The embodiments of the present invention will be further described below with reference to the accompanying drawings. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain embodiments of the present invention, and should not be construed as limiting the present invention.

[0026] In the description of the embodiments of the present invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] Example 1 (5-inch sapphire wafer, cutting direction selected as +60°) This embodiment provides a multi-wire dicing method for sapphire wafers. Please refer to [link / reference]. Figure 1 As shown, the process includes the following steps S01 to S05: S01, a sapphire crystal rod is provided; the normal of the cut surface of the sapphire crystal rod is deflected by a preset deflection angle relative to its optical axis direction toward an initial crystal orientation in a base plane, and the projection direction of the cut surface normal on the base plane is parallel to the initial crystal orientation; the base plane contains a plurality of equivalent crystal orientations that have a crystallographic equivalent relationship with the initial crystal orientation and are periodically distributed with a preset phase difference.

[0029] Specifically, this embodiment provides a 5-inch (Φ125mm) sapphire crystal rod with a length of 600mm. The c-axis direction of the sapphire crystal rod is accurately determined using an X-ray diffractometer (XRD, model Bruker D8 Discover, accuracy ±0.01°), and the orientation of the basal plane (i.e., the (0001) plane) is verified by optical imaging method.

[0030] S02, determine the base plane of the sapphire crystal rod, determine the projection direction of the cut surface normal on the base plane, and record the projection direction as the first reference crystal direction.

[0031] Specifically, within the measured datum plane, the projection direction of the cut surface normal onto the datum plane is determined. This projection direction is parallel to the original preset initial crystal orientation, and this projection direction is denoted as the first reference crystal orientation (i.e., the conventional A0 direction). At this time, the cut surface normal of the sapphire crystal rod is deflected by a preset deflection angle relative to its optical axis (c-axis) toward this initial crystal orientation (A0 direction), that is, the angle between the cut surface normal and the c-axis is 89.2° (corresponding to C deflection A 0.8±0.05°).

[0032] S03, taking the first reference crystal orientation as a reference, select an equivalent crystal orientation in the base plane that differs from the first reference crystal orientation by the preset phase difference, and use it as the cutting orientation.

[0033] Specifically, based on the crystallographic properties of the hexagonal crystal system of sapphire, its basal plane contains six equivalent A-axis (equivalent crystal directions) periodically distributed with a predetermined phase difference (60°). After determining the first reference crystal direction (A0), the adjacent A-axis direction that differs from the A0 direction by a predetermined phase difference (+60°) is selected as the final cutting direction (i.e., A). + direction).

[0034] S04, with the first reference crystal orientation as the rotation axis, rotate the sapphire crystal rod around the rotation axis by the preset phase difference, so that the wire saw feed direction of the multi-wire cutting machine is along the infeed crystal orientation.

[0035] Specifically, the sapphire crystal rod is rotated +60° around the first reference crystal orientation (i.e., the A0 direction, which is not a crystallographic rotation axis but a spatial orientation reference) as the rotation axis. This operation ensures that the feed direction of the diamond wire saw of the multi-wire cutting machine is strictly along the entry crystal orientation (A0 direction) selected in step S03. + The rotation is performed in the direction of the crystal rod. It should be noted here that after this step of rotation, the spatial tilt angle of the crystal rod (i.e., the angle between the normal of the cutting surface and the c-axis, which is 89.2°) remains absolutely unchanged; only the azimuth angle within the base plane changes.

[0036] S05, set the cutting parameters and start the multi-wire cutting machine to cut the rotated sapphire ingot to obtain a sapphire wafer.

[0037] Specifically, the cutting parameters set in this embodiment are as follows: diamond wire saw wire diameter of 0.20 mm, wire speed of 1800 m / min, tension of 35 N, and cutting fluid flow rate of 50 L / min. After cutting, the wafer is removed and cleaned to obtain a 5-inch sapphire wafer with low warpage characteristics.

[0038] The test results for this embodiment are as follows: The surface shape and crystal orientation of the sapphire wafers obtained from the cutting process (sample size n=50 wafers) were measured, and the statistical results are as follows (mean / maximum): Warpage (Bow): Average 3.2 μm, maximum 4.8 μm (compliance rate 100%). Total warp: mean 32 μm, maximum 38 μm (100% compliance rate); Total thickness deviation (TTV): average 6.5 μm, maximum 9.2 μm (compliance rate 100%). XRD crystal orientation measurement deviation: mean 0.006°, maximum 0.009° (compliance rate 100%).

[0039] The physical mechanism of this embodiment is explained as follows: Please refer to Figures 2 to 4 The physical mechanism by which the present invention achieves the above-mentioned excellent effects lies in the fact that the cutting force field is balanced by changing the azimuth angle.

[0040] like Figure 2 As shown, sapphire belongs to the hexagonal crystal system, and its basal plane (0001) has six equivalent A-axis (equivalent crystal orientations) distributed within it, spaced 60° apart. The conventional A0 cutting direction is located in the crystal transition region between the c-axis and the adjacent A-axis; however, the A-axis of this invention... + Or A - The tool entry direction is located in the adjacent A-axis symmetric region of the pure phase.

[0041] like Figure 3 As shown, when using the traditional A0 direction for tool entry ( Figure 2 (Left) The elastic modulus of the sapphire crystals contacted by the wire saw on both sides exhibits a significant asymmetry. The elastic modulus E1 on the left is 410 GPa, while that on the right is 395 GPa, with a difference of ΔE = 15 GPa. This extreme asymmetry directly causes the wire saw to bend and deflect to one side (wire bow), resulting in the wire saw cutting path deviating from the ideal straight line.

[0042] like Figure 4 As shown, due to the offset of the wire saw, the cut wafer surface exhibits an "S-shaped twisted surface" with non-uniform diagonal twist. Figure 3 (Left), its Bow>15 μm, Warp>50 μm, TTV>15 μm, and surface distortion caused XRD crystal orientation measurement deviation>0.04°, which could not meet the stringent requirements for surface shape and crystal orientation accuracy in subsequent polishing and device fabrication of power devices.

[0043] By employing the technical means of steps S03 and S04 of this invention, the tool entry point is switched to A. + When the direction is correct, the elastic modulus of the crystals on both sides of the wire saw tends to be equal, with E1 on the left side being 405 GPa and E2 on the right side being 402 GPa. The difference in elastic modulus between the two sides is ΔE = 3 GPa (ΔE ≤ 5 GPa). In this state, the wire saw is straight and has no deviation. Figure 3 (Right), the cut wafer surface shape is reconstructed into a "saddle-symmetric" shape symmetrical along the central axis ( Figure 4 (Right), such that Bow ≤ 5 μm, Warp ≤ 40 μm, TTV ≤ 10 μm, and XRD crystal orientation measurement deviation < 0.01°.

[0044] Example 2 (4-inch sapphire wafer, cutting direction selected -60°) This embodiment also uses the process flow from S01 to S05 described above, only changing the ingot specifications and the cutting direction: Crystal rod specifications: 4-inch (Φ100mm) sapphire crystal rod.

[0045] Core step: In step S03, an equivalent crystal orientation that differs from the first reference crystal orientation by -60° is selected as the entry crystal orientation (i.e., A). - (Direction); In step S04, the sapphire crystal rod is rotated -60° around the first reference crystal direction.

[0046] Test results: The measured 4-inch sapphire wafers have a warp of ≤ 4 μm, a total warp of ≤ 30 μm, a total thickness deviation (TTV) of ≤ 8 μm, and an XRD crystal orientation measurement deviation of <0.008°, which is also a significant result.

[0047] Comparative Example 1 (Traditional A0 direction tool entry) The same 5-inch sapphire crystal rod and the same multi-wire cutting equipment and cutting parameters as in Example 1 are used. The only difference is that the cutting direction is not switched. That is, the cutting direction remains unchanged along the first reference crystal direction (A0) in step S03, and no rotation operation is performed in step S04.

[0048] Comparison results: such as Figure 5 As shown in the bar chart data, the sapphire wafer obtained in the comparative model exhibits severe S-shaped twist, with a warp > 15 μm, a total warp > 50 μm, and a total thickness deviation (TTV) > 15 μm. Figure 6 As shown in the scatter plot, due to Warp exceeding the limit, the XRD crystal orientation measurement deviation of the comparative wafers is generally >0.04°, which is much greater than the acceptable threshold (0.01°).

[0049] Based on the process details of Embodiment 1, Embodiment 2, and Comparative Example 1 above, the specific implementation conditions and effect data of each embodiment and comparative example are summarized in Table 1 below: Table 1. Comparison of specific parameters and effects between the examples and comparative examples.

[0050] In Table 1, the cutting parameters used in Examples 1, 2, and Comparative Example 1 were kept consistent: diamond wire saw diameter 0.20 mm, wire speed 1800 m / min, tension 35 N, and cutting fluid flow rate 50 L / min. That is, only the blade infeed direction was changed for comparative testing.

[0051] As can be seen from Examples 1-2 and Comparative Example 1 above, under the premise that the cutting parameters and spatial tilt angle (off-cut angle) remain absolutely unchanged, it is only necessary to switch the entry azimuth of the multi-wire cutting from the traditional first reference crystal direction (A0 direction) to the adjacent equivalent crystal direction (A0 direction) that differs by 60°. + Or A - By adjusting the direction, the difference in crystal elastic modulus (ΔE) on both sides of the wire saw can be drastically reduced from greater than 5 GPa to less than 5 GPa. This operation eliminates the lateral offset of the wire saw from a physical and mechanical perspective, thereby reconstructing the wafer surface shape from an uncontrollable "S-shaped twist" to a perfect "saddle symmetry," ensuring that the Bow, Warp, TTV, and XRD crystal orientation deviations all meet the stringent mass production standards in the power device field. Among them, Example 1 shows the best performance in all indicators on a 5-inch wafer and has the best industrialization and promotion value.

[0052] Other alternative implementation methods and parameter extensions are as follows: 1. Equipment Applicability: The method of this invention does not rely on the oscillating motion of the multi-wire cutting machine. In Embodiments 1 and 2 above, the multi-wire cutting machines used are all fixed multi-wire cutting machines, and the cutting process does not rely on the oscillating motion of the machine. Because this invention fundamentally solves the problem of lateral offset of the wire saw, there is no need to purchase expensive oscillating cutting machines. It can be seamlessly implemented on existing commercially available fixed multi-wire cutting production lines, greatly reducing the cost of process modification and production line upgrades.

[0053] 2. Process parameter range: During implementation, the cutting parameters of multi-wire cutting can be adjusted within a wide range. In addition to the specific parameters described in Example 1, this invention is also applicable to the following parameter ranges: diamond wire saw diameter of 0.15 ~ 0.25 mm, wire speed of 1200 ~ 2400 m / min, tension of 25 ~ 50 N, and cutting fluid flow rate of 30 ~ 80 L / min. Since this invention addresses the mechanical equilibrium problem caused by crystallographic symmetry, the above process parameters, as long as they are within the conventional multi-wire cutting process window, can achieve balanced force (ΔE ≤ 5 GPa) and a saddle-shaped symmetrical surface effect.

[0054] 3. Extension of crystal orientation and equivalent crystal orientation: In this invention, the "initial crystal orientation" refers to the a-axis crystal orientation, and the "equivalent crystal orientation" refers to the crystal orientation within the basal plane that differs from the a-axis crystal orientation by an integer multiple of 60°. Based on the crystallographic characteristics of sapphire α-Al₂O₃, the a-axis and m-axis families within its (0001) basal plane are alternately arranged, and both fall within the categories of the "A-axis" and "equivalent crystal orientation" as referred to in this embodiment along a 60° period. In actual implementation, the absolute value only needs to satisfy an integer multiple of (A₀ ± 60°) or an engineering error range of (A₀ ± 60° ± 5°) to achieve the low warpage cutting effect of this invention.

[0055] 4. Size compatibility: In addition to the 5-inch and 4-inch sapphire ingots mentioned above, the clamping and positioning method of this invention, by switching the standard ingot sticking fixture, can be fully applied to the processing of sapphire ingots of different diameters and lengths, possessing extremely strong industrial promotion value. In the implementation steps, the rotation operation of the ingot (S04) is coordinated with the feed direction of the multi-wire cutting machine, ensuring that regardless of the ingot size, as long as the above-mentioned crystallographic symmetry reversal principle is satisfied, S-shaped torsion can be eliminated, resulting in a saddle-symmetric low-warpage wafer.

[0056] In summary, a multi-wire dicing method for sapphire wafers has the following advantages: By switching the entry azimuth angle from the traditional initial crystal orientation (such as the A0 direction) to an adjacent equivalent crystal orientation with a preset phase difference (e.g., ±60°) within the basal plane, the stress point of the diamond wire saw during the initial cutting is shifted from the "cA crystal orientation transition zone" to the "equivalent crystal orientation pure symmetry zone". Experimental results show that this switching operation can significantly reduce the difference in elastic modulus (ΔE) between the sapphire crystals on both sides of the wire saw from over 15 GPa in existing technologies to 5 GPa or less, fundamentally eliminating the wire saw lateral offset (wire bow) caused by asymmetric force and ensuring the straightness of the cutting path.

[0057] Thanks to the effective suppression of lateral offset by the wire saw, the wafer surface after cutting completely eliminates the "S-shaped twisted surface" caused by non-uniform twisting along the diagonal direction in traditional processes, and is reconstructed into a "saddle-shaped symmetrical surface" symmetrical along the central axis. Based on actual measurement data from 5-inch wafer mass production, this invention reduces the warp from >15 μm in traditional processes to ≤5 μm (a reduction of more than 67%); the total warp from >50 μm to ≤40 μm (a reduction of more than 20%); and the total thickness deviation (TTV) from >15 μm to ≤10 μm (a reduction of more than 30%), fully meeting the stringent mass production standards for surface flatness in the power device field.

[0058] Because the "saddle-shaped" surface shape eliminates the crystal plane diffraction deviation caused by excessive warp, this invention effectively solves the long-standing industry problem of "excessive XRD measurement error due to surface distortion" in traditional processes. Actual measurements show that the crystal orientation measurement deviation of this invention is drastically reduced from >0.04° in traditional processes to <0.01°, precisely solving the yield loss problem caused by crystal orientation measurement errors in the fabrication of high-end power devices such as SiC-on-sapphire and GaNHEMT, and providing a high-precision substrate foundation for subsequent polishing and epitaxial processes.

[0059] The core improvement of this invention lies in the clamping and positioning step before cutting (i.e., rotating the crystal rod around a reference crystal direction with a preset phase difference). This method is simple to operate, has a clear mechanism, and high repeatability. It does not rely on expensive swing-type multi-wire cutting machines and can be directly adapted to existing commercially available fixed multi-wire cutting equipment without any hardware upgrades or modifications, significantly reducing production line upgrade costs for enterprises. Furthermore, this method is compatible with 4-inch, 5-inch, and various other sizes of sapphire crystal rods, with a wide range of process parameters (e.g., wire diameter 0.15~0.25mm, wire speed 1200~2400m / min), making it widely applicable and possessing strong industrial promotion value.

[0060] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A multi-wire dicing method for sapphire wafers, characterized in that, Includes the following steps: A sapphire crystal rod is provided; the normal of the cut surface of the sapphire crystal rod is deflected by a preset deflection angle relative to its optical axis direction toward an initial crystal orientation in a base plane, and the projection direction of the cut surface normal on the base plane is parallel to the initial crystal orientation; the base plane contains a plurality of equivalent crystal orientations that have crystallographic equivalent relationships with the initial crystal orientation and are periodically distributed with a preset phase difference. The base plane of the sapphire crystal rod is measured, and the projection direction of the normal of the cut surface on the base plane is determined within the base plane, and this projection direction is recorded as the first reference crystal direction; Using the first reference crystal orientation as a reference, an equivalent crystal orientation that differs from the first reference crystal orientation by the preset phase difference is selected in the base plane and used as the cutting crystal orientation. Using the first reference crystal orientation as the rotation axis, the sapphire crystal rod is rotated around the rotation axis by the preset phase difference, so that the wire saw feed direction of the multi-wire cutting machine is along the infeed crystal orientation; Set the cutting parameters and start the multi-wire cutting machine to cut the rotated sapphire ingot to obtain a sapphire wafer.

2. The multi-wire dicing method for sapphire wafers according to claim 1, characterized in that, The preset deflection angle is 0.75~0.85°, and the preset phase difference is 55~65°.

3. The multi-wire dicing method for sapphire wafers according to claim 1, characterized in that, The set cutting parameters include: a diamond wire saw wire diameter of 0.15~0.25 mm, a wire speed of 1200~2400 m / min, a tension of 25~50 N, and a cutting fluid flow rate of 30~80 L / min.

4. The multi-wire dicing method for sapphire wafers according to claim 1, characterized in that, An equivalent crystal orientation with a difference of +55° to +65° from the first reference crystal orientation is selected within the base plane as the cutting orientation, and the sapphire crystal rod is rotated by +55° to +65° around the first reference crystal orientation.

5. The multi-wire dicing method for sapphire wafers according to claim 1, characterized in that, An equivalent crystal orientation that differs from the first reference crystal orientation by -55° to -65° within the base plane is selected as the cutting orientation, and the sapphire crystal rod is rotated by -55° to -65° around the first reference crystal orientation.

6. The multi-wire dicing method for sapphire wafers according to claim 1, characterized in that, The sapphire crystal obtained after cutting is round enough to meet the following measurement parameters for shape and crystal orientation: warp ≤ 5 μm, total warp ≤ 40 μm, total thickness deviation (TTV) ≤ 10 μm, and XRD crystal orientation measurement deviation < 0.01°.

7. The multi-wire dicing method for sapphire wafers according to claim 1, characterized in that, The multi-wire cutting machine is a fixed multi-wire cutting machine, and the cutting process does not depend on the oscillating motion of the multi-wire cutting machine.

8. The multi-wire dicing method for sapphire wafers according to claim 1, characterized in that, The sapphire crystal rod is a 4-inch or 5-inch sapphire crystal rod.

9. The multi-wire dicing method for sapphire wafers according to claim 1, characterized in that, After performing the above steps to make the wire saw feed direction of the multi-wire cutting machine along the cutter crystal direction, the difference in crystal elastic modulus ΔE on both sides of the diamond wire saw is ≤ 5 GPa.

10. The multi-wire dicing method for sapphire wafers according to claim 1, characterized in that, The initial crystal orientation is the a-axis crystal orientation, and the equivalent crystal orientation is the crystal orientation in the basal plane that differs from the a-axis crystal orientation by an integer multiple of 60°.

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