Silicon carbide substrate and laser lift-off method for simultaneously processing multiple silicon carbide substrates

Abstract

The invention provides silicon carbide substrates and a laser lift-off method for simultaneously processing multiple silicon carbide substrates. The laser lift-off method comprises the following steps: S1, laser is divided into at least two beams of laser after passing through an optical diffraction wafer; s2, at least two laser beams in the step S1 are vertically incident on the surface of the silicon carbide crystal bar; and S3, focal points are formed on focal planes of different depths of the silicon carbide crystal bar through a focusing lens, meanwhile, laser lift-off processing is carried out, and multiple silicon carbide substrates which are processed at the same time are obtained. According to the laser lift-off method for simultaneously processing the plurality of silicon carbide substrates, more than two silicon carbide substrates can be simultaneously processed by one laser, so that the processing efficiency is improved, and the time cost caused by laser lift-off single-chip discharging operation is reduced.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide stripping technology, and more specifically, to a silicon carbide substrate and a laser stripping method for simultaneously processing multiple silicon carbide substrates. Background Technology

[0002] Currently, there are two main methods for processing silicon carbide ingots: multi-wire cutting and laser lift-off. Multi-wire cutting is the most mature processing method, but it suffers from problems such as high processing stress, low wafer yield per millimeter, and deep damage layers. Laser lift-off, on the other hand, offers advantages such as low processing stress, excellent warpage and curvature, and minimal processing damage, effectively increasing the wafer yield per ingot and reducing material waste. In practical applications, laser lift-off is a single-wafer processing mode. Although the processing time for a single wafer is shorter than that of multi-wire cutting, it still presents challenges for large-scale production, such as low efficiency due to the back-and-forth handling of ingots. This solution addresses these issues by seeking a method to improve the efficiency of laser lift-off processing of silicon carbide substrates. Summary of the Invention

[0003] To address the above problems, the present invention provides a laser lift-off method for simultaneously processing multiple silicon carbide substrates, comprising the following steps:

[0004] S1: The laser beam is split into at least two beams after passing through an optical diffraction crystal;

[0005] S2: At least two laser beams from step S1 are incident perpendicularly onto the surface of the silicon carbide crystal rod;

[0006] S3: Then, a focal point is formed at a focal plane at different depths of the silicon carbide crystal rod through a focusing lens, and laser lift-off processing is performed simultaneously to obtain multiple silicon carbide substrates processed at the same time. In this invention, processing multiple silicon carbide substrates simultaneously refers to processing at least two silicon carbide substrates simultaneously.

[0007] The infrared laser generator of this application emits laser light, which is split into at least two laser beams by an optical diffraction crystal. More specifically, the optical diffraction crystal can be a diffraction beam splitter (DBS).

[0008] Optionally, the height difference between two adjacent focal points is not less than 500 μm, that is, the height difference between two adjacent focal points in the vertical (axial) direction of the silicon carbide crystal rod is not less than 500 μm.

[0009] Optionally, the height difference between two adjacent focal points is not less than 700 μm. Optionally, the height difference between two adjacent focal points is not less than 900 μm.

[0010] Furthermore, by further controlling the height difference between two adjacent focal points, this application can ensure the isolation of heat-affected zones, preventing damage to the silicon carbide internal lattice due to thermal stress concentration, and improving the quality of the silicon carbide substrate lift-off sheet. Simultaneously, because the focal points of the laser used are formed by splitting the same laser beam, the consistency and stability of the laser spot are ensured. Precise control can reduce the surface roughness of the silicon carbide substrate and the depth of the damaged layer.

[0011] Optionally, in step S2, the distance between two adjacent laser beams does not exceed 200 μm, that is, the distance between two adjacent laser beams in the horizontal direction of the silicon carbide crystal rod does not exceed 200 μm.

[0012] Optionally, the distance between two adjacent laser beams in step S2 shall not exceed 100 μm.

[0013] Furthermore, by controlling the distance between two adjacent laser beams, this application can ensure the consistency of the processing, thereby enabling the simultaneous formation of a flat silicon carbide substrate laser thermal effect layer inside silicon carbide crystal rods of different thicknesses, thus improving processing efficiency.

[0014] Optionally, in step S1, the laser wavelength is 1020-1080nm, the pulse width is no more than 20ps, the repetition frequency is no less than 100kHz, and the power is no more than 20W.

[0015] Optionally, the extinction ratio of the optical diffraction crystal is less than 10^-6, the field of view is greater than 6°, and the angular tolerance is less than 3 arcseconds.

[0016] In this application, by controlling the performance indicators of the optical diffraction wafer, the extinction ratio of less than 10^-6 can suppress stray light interference and prevent stray light from causing material modification in unplanned areas. The field of view is greater than 6° and the angle tolerance is less than 3 arcseconds, which can improve the stability of the split laser and ensure that the multiple silicon carbide substrates obtained simultaneously have low variability and high quality.

[0017] Optionally, step S2 may further include the following steps:

[0018] S21: Convert at least two laser beams into parallel light through a collimating lens;

[0019] S22: Parallel light is shaped and modulated by a spatial light modulator; optionally, during the optical wave modulation process, the wavefront distortion of the split laser is less than λ / 10, the relative deviation of the light intensity of each beam is <2%, and the center offset is <1% of the beam diameter.

[0020] S23: The laser beams after beam shaping and wave modulation are passed through a mirror so that at least two laser beams are incident perpendicularly on the surface of the silicon carbide crystal rod.

[0021] Optionally, the collimating lens has a focusing length of 30-70mm, a wavelength range of 400-2000nm, and an effective aperture of no more than 30mm.

[0022] Optionally, the collimating lens has a focusing length of 40-60mm, a wavelength range of 800-1500nm, and an effective aperture of no more than 20mm.

[0023] Optionally, the spot diameter ranges from 1 to 50 μm, and the spot shape is one of ellipse, ellipsoid, sphere, or ring. Optionally, the spot diameter ranges from 10 to 30 μm. By controlling the spot diameter, cracks can be controlled, and the surface roughness and damage layer depth of the silicon carbide substrate can be reduced.

[0024] Another aspect of the present invention provides a laser lift-off method for simultaneously processing multiple silicon carbide substrates to obtain silicon carbide substrates, wherein the surface roughness difference of the simultaneously processed multiple silicon carbide substrates is less than 5%. Optionally, the surface roughness difference of the simultaneously processed multiple silicon carbide substrates is less than 3%. Optionally, the surface roughness difference of the simultaneously processed multiple silicon carbide substrates is less than 10%. Optionally, the surface roughness difference of the simultaneously processed multiple silicon carbide substrates is less than 15%.

[0025] Optionally, the difference in the depth of the damaged layer of multiple silicon carbide substrates processed simultaneously is no greater than 15%. Optionally, the difference in the depth of the damaged layer of multiple silicon carbide substrates processed simultaneously is no greater than 20%. Optionally, the difference in the depth of the damaged layer of multiple silicon carbide substrates processed simultaneously is no greater than 10%.

[0026] Optionally, the surface roughness of any monolithic silicon carbide substrate is less than 35 μm, and the depth of the damaged layer of any monolithic silicon carbide substrate is less than 105 μm.

[0027] Compared with the prior art, the present invention achieves at least one of the following beneficial effects:

[0028] (1) The laser lift-off method for processing multiple silicon carbide substrates simultaneously: A laser can process two or more silicon carbide substrates at the same time, which improves processing efficiency and reduces the time cost caused by single-piece laser lift-off operation.

[0029] (2) The laser lift-off method for simultaneously processing multiple silicon carbide substrates of the present invention ensures that the subsequently obtained multiple silicon carbide substrates have low variability. For example, the surface roughness difference of the simultaneously processed multiple silicon carbide substrates is less than 15%, and the difference in the depth of the damaged layer of the simultaneously processed multiple silicon carbide substrates is no greater than 20%. Preferably, the surface roughness difference of the simultaneously processed multiple silicon carbide substrates is less than 5%, and the difference in the depth of the damaged layer of the simultaneously processed multiple silicon carbide substrates is no greater than 10%.

[0030] (3) The silicon carbide substrates obtained by the laser lift-off method for processing multiple silicon carbide substrates simultaneously according to the present invention have high quality, with the surface roughness of any single substrate being less than 35 μm and the depth of the damaged layer of any single substrate being less than 105 μm. Preferably, the surface roughness of any single substrate is less than 10 μm and the depth of the damaged layer of any single substrate is less than 70 μm. Attached Figure Description

[0031] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 An exemplary embodiment of the apparatus flowchart of the laser lift-off method for simultaneously processing two silicon carbide substrates according to the present invention is shown.

[0033] Explanation of reference numerals in the attached figures:

[0034] 101-Infrared laser; 102-Diffraction beam splitter; 103-Collimating lens; 104-Spatial light modulator; 105-Reflecting mirror; 106-Focusing lens; 107-Silicon carbide crystal rod. Detailed Implementation

[0035] To more clearly illustrate the overall concept of the present invention, a detailed description will be provided below with reference to the accompanying drawings and examples.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0037] Furthermore, in the description of this invention, it should be understood that the terms "top," "bottom," "inner," "outer," "axial," "radial," "circumferential," 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 this 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 this invention.

[0038] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] In this invention, unless otherwise expressly specified and limited, the first feature "on" or "below" the second feature may be in direct contact with the first and second features, or indirect contact through an intermediate medium. In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0040] Example 1

[0041] In an exemplary embodiment of the present invention, the laser lift-off method for simultaneously processing two silicon carbide substrates includes the following steps:

[0042] S1: The infrared laser generator 101 emits a laser beam, which is then split by the diffraction beam splitter DBS102 to produce two laser beams.

[0043] The laser has a wavelength of 1020nm, a pulse width of 20ps, a repetition frequency of 100kHz, and a power of 20W.

[0044] The extinction ratio of the optical diffraction crystal is 5*10^-7, the field of view is 7°, and the angular tolerance is 2 arcseconds.

[0045] S21: The collimating lens 103 converts the two laser beams into two parallel beams.

[0046] The collimating lens has a focusing length of 30mm, a wavelength range of 400nm, and an effective aperture of 30mm.

[0047] S22: After passing through the spatial light modulator 104, the two parallel beams undergo spot shaping and wave modulation to adjust the spot into a spherical shape with a diameter of 1 μm. During wave modulation, the wavefront distortion of the split laser is less than λ / 10, the relative intensity deviation of each beam is <2%, and the center offset is <1% of the beam diameter.

[0048] S23: The laser beam after beam shaping and wave modulation is acted upon by the reflector 105 to change the propagation direction of the laser beam, so that the two laser beams are perpendicularly incident on the surface of the silicon carbide crystal rod, and the distance between the two laser beams is 200μm.

[0049] S3: Finally, through the focusing lens 106, focal points are formed at different depths of the silicon carbide crystal rod, completing the simultaneous laser lift-off processing of two substrates. Because the focal depths of the lasers are different, two silicon carbide lift-off substrates can be processed simultaneously. The height difference h1 between the two focal points is 500 μm. See the flowchart of the laser lift-off method apparatus for reference. Figure 1 As shown.

[0050] Example 2

[0051] In an exemplary embodiment of the present invention, the laser lift-off method for simultaneously processing two silicon carbide substrates includes the following steps:

[0052] S1: The infrared laser generator 101 emits a laser beam, which is then split by the diffraction beam splitter DBS102 to produce two laser beams.

[0053] The laser has a wavelength of 1080nm, a pulse width of 10ps, a repetition frequency of 200kHz, and a power of 10W.

[0054] The extinction ratio of the optical diffraction crystal is 1*10^-7, the field of view is 10°, and the angular tolerance is 1 arcsecond.

[0055] S21: The collimating lens 103 converts the two laser beams into two parallel beams.

[0056] The collimating lens has a focusing length of 70mm, a wavelength range of 2000nm, and an effective aperture of 10mm.

[0057] S22: Two parallel beams are passed through spatial light modulator 104 for beam spot shaping and wave modulation, adjusting the beam spot to a spherical shape with a diameter of 50 μm. During wave modulation, the wavefront distortion of the split laser is less than λ / 10, the relative deviation of the beam intensity is <1%, and the center offset is <1% of the beam diameter.

[0058] S23: The laser beam after beam shaping and wave modulation is acted upon by the reflector 105 to change the propagation direction of the laser beam, so that the two laser beams are perpendicularly incident on the surface of the silicon carbide crystal rod, and the distance between the two laser beams is 100μm.

[0059] S3: Finally, through the focusing lens 106, focal points are formed at different depths of the silicon carbide crystal rod, completing the simultaneous laser lift-off processing of two substrates. Because the focal depths of the lasers are different, two silicon carbide lift-off substrates can be processed simultaneously. The height difference between the two focal points is 700 μm. See the flowchart of the laser lift-off method apparatus for reference. Figure 1 As shown.

[0060] Example 3

[0061] In an exemplary embodiment of the present invention, the laser lift-off method for simultaneously processing two silicon carbide substrates includes the following steps:

[0062] S1: The infrared laser generator 101 emits a laser beam, which is then split by the diffraction beam splitter DBS102 to produce two laser beams.

[0063] The laser has a wavelength of 1050nm, a pulse width of 10ps, a repetition frequency of 300kHz, and a power of 5W.

[0064] The extinction ratio of the optical diffraction crystal is 5*10^-8, the field of view is 15°, and the angular tolerance is 1 arcsecond.

[0065] S21: The collimating lens 103 converts the two laser beams into two parallel beams.

[0066] The collimating lens has a focusing length of 50mm, a wavelength range of 1000nm, and an effective aperture of 5mm.

[0067] S22: Two parallel beams are passed through spatial light modulator 104 for spot shaping and wave modulation, adjusting the spot to a spherical shape with a diameter of 20μm. During wave modulation, the wavefront distortion of the split laser is less than λ / 10, the relative intensity deviation of each beam is <1%, and the center offset is <1% of the beam diameter.

[0068] S23: The laser beam after beam shaping and wave modulation is acted upon by the reflector 105 to change the propagation direction of the laser beam, so that the two laser beams are perpendicularly incident on the surface of the silicon carbide crystal rod, and the distance between the two laser beams is 50μm.

[0069] S3: Finally, through the focusing lens 106, focal points are formed at different depths of the silicon carbide crystal rod, completing the simultaneous laser lift-off processing of two substrates. Because the focal depths of the lasers are different, two silicon carbide lift-off substrates can be processed simultaneously. The height difference between the two focal points is 750 μm. See the flowchart of the laser lift-off method apparatus for reference. Figure 1 As shown.

[0070] Example 4

[0071] The main difference from Example 1 is that the infrared laser generator 101 emits a laser beam, which is then split by the diffractometer DBS102 to generate three laser beams, simultaneously processing three silicon carbide lift-off substrates. Other parameters and steps are the same as in Example 1.

[0072] Example 5

[0073] The main difference from Example 1 is that the laser wavelength is 900nm, the pulse width is 25ps, the repetition frequency is 90kHz, and the power is 20W.

[0074] Example 6

[0075] Based on Example 1, the main difference is that the extinction ratio of the optical diffraction crystal is 2*10^-6, the field of view is 5°, and the angular tolerance is 4 arcseconds.

[0076] Example 7

[0077] Based on Example 1, the main difference is that the spot diameter is 80μm.

[0078] Example 8

[0079] The main difference from Example 1 is that the height difference between the two focal points is 300 μm.

[0080] Comparative Example 1

[0081] In an exemplary embodiment of the present invention, the laser lift-off method for a silicon carbide substrate includes the following steps:

[0082] S1: The infrared laser generator 101 emits a laser beam, generating a laser beam.

[0083] The laser has a wavelength of 1020nm, a pulse width of 20ps, a repetition frequency of 100kHz, and a power of 20W.

[0084] S21: The laser beam is converted into a parallel beam by collimating lens 103;

[0085] The collimating lens has a focusing length of 30mm, a wavelength range of 400nm, and an effective aperture of 30mm.

[0086] S22: After the parallel light passes through the spatial light modulator 104, the light spot is shaped and the light wave is modulated to adjust the light spot into a spherical shape with a diameter of 1μm.

[0087] S23: The laser beam after beam shaping and wave modulation is acted upon by the reflector 105 to change the propagation direction of the laser, so that the laser beam is perpendicularly incident on the surface of the silicon carbide crystal rod.

[0088] S3: Finally, through the function of the focusing lens 106, a focal point is formed on the focal plane of the silicon carbide crystal rod, and the laser lift-off process of the single substrate is completed.

[0089] The silicon carbide substrates obtained in the above embodiments and comparative examples were subjected to performance tests. The surface roughness was measured using a white light interferometer, and the damage layer depth was measured using SEM. The test results are shown in Table 1.

[0090] Table 1

[0091]

[0092]

[0093] Referring to Table 1, the laser lift-off method for simultaneously processing multiple silicon carbide substrates of the present invention uses one laser to process two or more silicon carbide substrates simultaneously, which can improve processing efficiency and reduce the time cost caused by single-substrate removal operations during laser lift-off. The resulting multiple silicon carbide substrates exhibit low variability; for example, the surface roughness difference between the simultaneously processed substrates is less than 15%, and the difference in damaged layer depth is no greater than 20%. Preferably, the surface roughness difference between the simultaneously processed substrates is less than 5%, and the difference in damaged layer depth is no greater than 10%.

[0094] Furthermore, the laser lift-off method for simultaneously processing multiple silicon carbide substrates of the present invention produces high-quality silicon carbide substrates, with the surface roughness of any single substrate being less than 35 μm and the damage layer depth of any single substrate being less than 105 μm. Preferably, the surface roughness of any single substrate is less than 10 μm and the damage layer depth of any single substrate is less than 70 μm.

[0095] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A laser lift-off method for simultaneously processing multiple silicon carbide substrates, characterized in that, Includes the following steps: S1: The laser beam is split into at least two beams after passing through an optical diffraction crystal; S2: At least two laser beams from step S1 are incident perpendicularly onto the surface of the silicon carbide crystal rod; S3: Then, a focal point is formed at a focal plane at different depths of the silicon carbide crystal rod through a focusing lens, and laser lift-off processing is performed at the same time to obtain multiple silicon carbide substrates processed simultaneously.

2. The laser lift-off method for simultaneously processing multiple silicon carbide substrates according to claim 1, characterized in that, The height difference between two adjacent focal points is not less than 500 μm.

3. The laser lift-off method for simultaneously processing multiple silicon carbide substrates according to claim 1, characterized in that, In step S2, the distance between two adjacent laser beams does not exceed 200 μm.

4. The laser lift-off method for simultaneously processing multiple silicon carbide substrates according to claim 1, characterized in that, In step S1, the laser wavelength is 1020-1080nm, the pulse width is no more than 20ps, the repetition frequency is no less than 100kHz, and the power is no more than 20W.

5. The laser lift-off method for simultaneously processing multiple silicon carbide substrates according to claim 1, characterized in that, The extinction ratio of the optical diffraction crystal is less than 10^-6, the field of view is greater than 6°, and the angular tolerance is less than 3 arcseconds.

6. The laser lift-off method for simultaneously processing multiple silicon carbide substrates according to claim 1, characterized in that, Step S2 also includes the following steps: S21: Convert at least two laser beams into parallel light through a collimating lens; S22: Parallel light is shaped and modulated by a spatial light modulator; S23: The laser beams after beam shaping and wave modulation are passed through a mirror so that at least two laser beams are incident perpendicularly on the surface of the silicon carbide crystal rod.

7. The laser lift-off method for simultaneously processing multiple silicon carbide substrates according to claim 6, characterized in that, The focusing length of the collimating lens is 30-70mm, the wavelength range is 400-2000nm, and the effective aperture is no more than 30mm.

8. The laser lift-off method for simultaneously processing multiple silicon carbide substrates according to claim 6, characterized in that, The spot diameter ranges from 1 to 50 μm, and the spot shape is one of ellipse, ellipsoid, sphere or ring.

9. A silicon carbide substrate obtained by a laser lift-off method for simultaneously processing multiple silicon carbide substrates as described in any one of claims 1-8, characterized in that, The surface roughness difference of the multiple silicon carbide substrates processed is less than 5%.

10. The silicon carbide substrate obtained by the laser lift-off method for simultaneously processing multiple silicon carbide substrates according to claim 9, characterized in that, Meanwhile, the depth difference of the damaged layer of multiple silicon carbide substrates processed is no greater than 10%.

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