CN115502586A - Silicon carbide cutting method - Google Patents

Silicon carbide cutting method Download PDF

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Publication number
CN115502586A
CN115502586A CN202211322496.5A CN202211322496A CN115502586A CN 115502586 A CN115502586 A CN 115502586A CN 202211322496 A CN202211322496 A CN 202211322496A CN 115502586 A CN115502586 A CN 115502586A
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CN
China
Prior art keywords
hydrogen ion
processing
silicon carbide
ion implantation
scanning
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Pending
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CN202211322496.5A
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Chinese (zh)
Inventor
文志东
侯煜
张喆
张昆鹏
李曼
石海燕
张紫辰
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Institute of Microelectronics of CAS
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Institute of Microelectronics of CAS
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Application filed by Institute of Microelectronics of CAS filed Critical Institute of Microelectronics of CAS
Priority to CN202211322496.5A priority Critical patent/CN115502586A/en
Publication of CN115502586A publication Critical patent/CN115502586A/en
Pending legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/50—Working by transmitting the laser beam through or within the workpiece
    • B23K26/57—Working by transmitting the laser beam through or within the workpiece the laser beam entering a face of the workpiece from which it is transmitted through the workpiece material to work on a different workpiece face, e.g. for effecting removal, fusion splicing, modifying or reforming
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/70—Auxiliary operations or equipment

Abstract

The invention provides a silicon carbide cutting method, which comprises the following steps: arranging a plurality of parallel processing paths on the surface of the silicon carbide crystal ingot; wherein each processing path has a plurality of processing points; performing hydrogen ion implantation at each processing point of each processing path to form at least one hydrogen ion implanted layer arranged in a vertical direction; and scanning the hydrogen ion implantation layer along each processing path according to the distribution of the plurality of processing points by adopting laser beams so as to realize the stripping of the silicon carbide wafer. The silicon carbide cutting method provided by the invention can reduce the material loss in the silicon carbide cutting process, improve the uniformity and yield of the silicon carbide wafer, and is beneficial to the preparation of thinner silicon carbide wafers.

Description

Silicon carbide cutting method
Technical Field
The invention relates to the technical field of semiconductors, in particular to a silicon carbide cutting method.
Background
The SiC substrate processing technology is an important basis for manufacturing devices, the quality and the precision of surface processing of the SiC substrate directly influence the quality of an epitaxial film and the performance of the devices, and therefore, the surface of a wafer is required to be ultra-smooth, defect-free and damage-free in application, and the surface roughness value reaches below a nanometer level. Because the SiC crystal has the characteristics of high hardness, high brittleness, good wear resistance and extremely stable chemical properties, the processing of the SiC wafer becomes very difficult. The SiC crystal bar is cut into wafers with small warpage, uniform thickness and low cutting loss, and is vital to subsequent grinding and polishing.
At present, the cutting method is widely applied to wire cutting and double-laser processing methods of silicon carbide crystal ingots. The multi-wire cutting process principle is as follows: the multi-wire cutting process is to cut the crystal ingot into cutting pieces with flat surfaces and uniform thickness according to a certain crystal direction so as to facilitate the subsequent grinding processing. And (3) double-laser beam cutting processing, namely, firstly using a laser beam to form a modified layer, and then using a laser beam to heat to control the growth of cracks until the cracks are broken. Both of these methods have the problems of low efficiency and large material loss during the cutting process.
Disclosure of Invention
The silicon carbide cutting method provided by the invention can reduce the material loss in the silicon carbide cutting process, improve the uniformity and yield of the silicon carbide wafer, and is beneficial to the preparation of thinner silicon carbide wafers. .
The invention provides a silicon carbide cutting method, which comprises the following steps:
arranging a plurality of parallel processing paths on the surface of the silicon carbide crystal ingot; wherein each machining path has a plurality of machining points;
performing hydrogen ion implantation at each processing point of each processing path to form at least one hydrogen ion implanted layer arranged in a vertical direction;
and scanning the hydrogen ion implantation layer along each processing path according to the distribution of the plurality of processing points by adopting laser beams so as to realize the stripping of the silicon carbide wafer.
Optionally, scanning, with a laser beam, the top hydrogen ion implantation layer sequentially along each processing point of each processing path to peel off the silicon carbide wafer includes:
and scanning for multiple times along one processing path according to the distribution of the plurality of processing point positions, and starting scanning of the next processing path after the scanning is finished.
Optionally, during each scan after the first scan, the polarization direction of the laser beam is perpendicular to the silicon carbide crystal growth direction, so that the crack propagation direction forms an angle of 4 ° with the horizontal direction.
Optionally, the number of scanning according to the distribution of the plurality of machining points along one machining path is 3-5.
Optionally, performing hydrogen ion implantation at each processing site of each processing path comprises:
the dosage of hydrogen ions implanted into the single hydrogen ion implantation layer at each processing point of each processing path is 5 × 10 16 /cm 2 To 1X 10 17 /cm 2 。
Optionally, the interval between two adjacent processing paths is 20-40 μm.
Optionally, when scanning the predetermined depth of each processing point of each processing path with the laser beam, the pulse width of the laser beam is 5ns to 50ns.
Alternatively, the performing of the hydrogen ion implantation at each processing site of each processing path to form at least one hydrogen ion implantation layer arranged in the vertical direction includes:
sequentially and upwards completing hydrogen ion implantation of each hydrogen ion implantation layer with the corresponding depth from the corresponding depth of the hydrogen ion implantation layer at the bottommost layer, wherein the step of performing hydrogen ion implantation at the corresponding depth of each hydrogen ion implantation layer comprises the following steps: hydrogen ion implantation is performed to each process site of each process path.
Optionally, scanning the hydrogen ion implantation layer along each processing path according to the distribution of the plurality of processing points with a laser beam to realize the stripping of the silicon carbide wafer includes:
and sequentially finishing the laser beam scanning of each hydrogen ion implantation layer downwards by the topmost hydrogen ion implantation layer, wherein the laser beam scanning of each hydrogen ion implantation layer comprises the following steps: and scanning the laser beams according to the processing point distribution along each processing path.
Alternatively, after each completion of scanning of one hydrogen ion implanted layer, a portion of the silicon carbide ingot above the hydrogen ion implanted layer on which the scanning was completed is peeled off, and after the peeling is completed, the surface of the remaining portion of the silicon carbide ingot is subjected to a flattening treatment.
In the technical scheme provided by the invention, a certain concentration H is injected into a layer with a certain depth of the silicon carbide crystal ingot + And point defects are formed. Then, the laser (with the pulse width of ns level) is adopted to focus on H + Multiple cavities are formed by overlapping the point defects under heating, and H is released to form H in the cavities 2 . And the pressure in the cavities continuously rises along with the laser scanning process to generate bubbles and cracks, and the silicon carbide wafer can be peeled off when the cracks of the cavities are connected together along with the extension of the cracks.
Drawings
FIG. 1 is a flow chart of a method for cutting silicon carbide according to an embodiment of the present invention;
fig. 2 is a schematic processing diagram of a silicon carbide cutting method according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The embodiment of the present invention provides a method for cutting silicon carbide, as shown in fig. 1, including:
step 100, arranging a plurality of parallel processing paths on the surface of a silicon carbide ingot; wherein each machining path has a plurality of machining points;
in some embodiments, the process path refers to a path that creates physical damage to the interior of the silicon carbide ingot. During slicing of the silicon carbide ingot, the silicon carbide wafer may be stripped from the silicon carbide ingot by physically breaking the plurality of paths and then breaking the regions between adjacent paths as the crack propagates. The machining point positions are the positions which are arranged on each machining path and form physical damage, and in the process of cutting the silicon carbide crystal ingot, the cutting of one machining path can be completed by forming physical damage on a plurality of the position positions and damaging the area between the adjacent position positions along with the extension of the crack.
Step 200, performing hydrogen ion implantation at each processing point of each processing path to form at least one hydrogen ion implantation layer arranged in the vertical direction;
in some embodiments, after the hydrogen ion implantation is completed, a plurality of hydrogen ion implanted layers are formed in the height direction of the silicon carbide ingot, as shown in the first drawing of fig. 2, in which 1 is the hydrogen ion implantation and 2 is a different hydrogen ion implanted layer. Since the hydrogen ion implantation and the subsequent laser processing process need different equipment, the silicon carbide ingot needs to move between the hydrogen ion implantation and the laser scanning process, and in order to reduce the moving steps of the silicon carbide ingot as much as possible and improve the efficiency, the hydrogen ion implantation of a plurality of hydrogen ion implantation layers can be completed at one time as much as possible. Because the diffusion capability of hydrogen ions in silicon carbide is weak, in the embodiment, hydrogen ions are implanted according to different processing paths and different processing point locations, and in the subsequent laser scanning process, laser scanning is performed according to different processing paths and different processing point locations, so that the position where laser is focused coincides with the position where the hydrogen ions are implanted, and the silicon carbide wafer can be successfully stripped.
And 300, scanning the hydrogen ion implantation layer along each processing path according to the distribution of a plurality of processing points by using laser beams so as to peel off the silicon carbide wafer.
In some embodiments, scanning the silicon carbide ingot with the laser beam means focusing the laser beam on the corresponding spot location to induce hydrogen ions to be extracted and to be accumulated to form hydrogen gas, and as the heat increases, the hydrogen gas pressure also increases to finally form bubbles and cracks on the corresponding spot location. The laser scanning process is shown in the second and third diagrams of fig. 2, wherein 3 is a silicon carbide ingot; 4 is short pulse laser; 5 is the laser scanning direction; and 6 is a hollow. In fig. 2, the positions of the respective spots are not shown, but the positions of the respective spots for hydrogen ion implantation and the positions of the respective spots for laser scanning coincide. In some preferred embodiments, the laser moves to the next path for scanning after repeatedly scanning the same path. During the first scanning, the processes of hydrogen ion precipitation and hydrogen gas formation are mainly induced, and the subsequent scanning process promotes the growth and connection of cracks. After the entire surface scan is completed, the silicon carbide wafer is peeled, as shown in the fourth drawing in fig. 2, and 7 is the peeled silicon carbide wafer.
In the technical scheme provided by the embodiment of the invention, a certain concentration H is injected into a layer with a certain depth of a silicon carbide crystal ingot + And point defects are formed. Then focusing on H by using laser (with the pulse width of ns level) + Multiple cavities are formed by overlapping the point defects under heating, and H is released to form H in the cavities 2 . And the pressure in the cavities continuously rises along with the laser scanning process to generate bubbles and cracks, and the silicon carbide wafer can be peeled off when the cracks of the cavities are connected together along with the extension of the cracks.
As an alternative embodiment, scanning the topmost hydrogen ion implantation layer sequentially by using a laser beam along each processing point of each processing path to realize the stripping of the silicon carbide wafer comprises:
and scanning for multiple times along one processing path according to the distribution of the plurality of processing point positions, and starting scanning of the next processing path after the scanning is finished.
In some embodiments, scanning a processing path refers to point-by-point focused irradiation of a plurality of spots with a laser beam along a path. The multiple scanning refers to that after the focused irradiation is finished point by point along one processing path, the focused irradiation is finished point by point along the path again, and the multiple scanning is executed in this way. For the multiple scanning process, the first scanning mainly induces the precipitation of hydrogen ions and the aggregation to form hydrogen gas, and the subsequent scanning mainly promotes the extension of cracks to realize stripping. In a preferred embodiment, the number of scans along a machining path is 3-5 times according to the distribution of machining points.
As an alternative embodiment, during each scan after the first scan, the polarization direction of the laser beam is perpendicular to the silicon carbide crystal growth direction, so that the crack propagation direction makes an angle of 4 ° with the horizontal direction. In some embodiments, the laser polarization direction is perpendicular to the silicon carbide crystal growth direction, so that the extension direction of the cracks can extend along the bottom surface of the silicon carbide hexagonal lattice, the smooth peeling of the silicon carbide wafer is facilitated, and the loss of materials is reduced.
As an alternative embodiment, performing hydrogen ion implantation at each process site of each process path comprises:
the dosage of hydrogen ions implanted into the single hydrogen ion implantation layer at each processing point of each processing path is 5 × 10 16 /cm 2 To 1X 10 17 /cm 2 。
In some embodiments, when the implantation amount of hydrogen ions is too large, the explosion stress is likely to be too large, which results in the breakage of the wafer, and when the implantation amount of hydrogen ions is too small, the crack generated by explosion is likely to be in a short range, which makes it difficult to complete the peeling of the wafer.
As an alternative embodiment, the interval between two adjacent processing paths is 20-40 μm.
As an alternative embodiment, the pulse width of the laser beam is 5ns to 50ns when the laser beam is used to scan a predetermined depth of each processing point of each processing path.
As an alternative embodiment, performing hydrogen ion implantation at each processing site of each processing path to form at least one hydrogen ion implanted layer arranged in a vertical direction includes:
the hydrogen ion implantation of the depth corresponding to each hydrogen ion implantation layer is sequentially completed upwards from the depth corresponding to the hydrogen ion implantation layer at the bottommost layer, wherein the hydrogen ion implantation performed at the depth corresponding to each hydrogen ion implantation layer comprises the following steps: hydrogen ion implantation is performed to each processing site of each processing path.
In some embodiments, when hydrogen ion implantation is performed on a plurality of hydrogen ion implanted layers, in order to avoid the influence of the hydrogen ion implanted layer formed first on the hydrogen ion implanted layer formed later, the hydrogen ion implanted layer is formed sequentially from bottom to top in the present embodiment, and the lower hydrogen ion implanted layer is formed first and the upper hydrogen ion implanted layer is formed later, so that no other hydrogen ion implanted layer exists above the corresponding depth every time hydrogen ion implantation is performed.
As an alternative embodiment, scanning the hydrogen ion implantation layer along each processing path according to the distribution of the plurality of processing points by using the laser beam to realize the stripping of the silicon carbide wafer comprises:
sequentially completing laser beam scanning of each hydrogen ion implantation layer from the topmost hydrogen ion implantation layer downwards, wherein the laser beam scanning of each hydrogen ion implantation layer comprises the following steps: and scanning the laser beams according to the processing point distribution along each processing path.
In some embodiments, during the laser scanning, the topmost hydrogen ion implanted layer is scanned first, and after the scanning is completed, the layer is stripped, and at this time, the second hydrogen ion implanted layer before the stripping becomes the latest topmost hydrogen ion implanted layer. The scanning mode is not influenced by other hydrogen ion implantation layers in the process of each scanning.
As an alternative embodiment, after each scanning of the hydrogen ion implanted layer is completed, a portion of the silicon carbide ingot above the hydrogen ion implanted layer on which the scanning is completed is peeled off, and after the peeling is completed, the surface of the remaining portion of the silicon carbide ingot is subjected to a planarization treatment.
In some embodiments, the surface of the silicon carbide ingot is not a flat surface after each layer is stripped, and the stripped surface is planarized to provide more precise focusing at a corresponding depth during laser focusing.
It will be understood by those skilled in the art that all or part of the processes of the embodiments of the methods described above may be implemented by a computer program, which may be stored in a computer-readable storage medium, and when executed, may include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (10)

1. A silicon carbide cutting method, comprising:
arranging a plurality of parallel processing paths on the surface of the silicon carbide crystal ingot; wherein each machining path has a plurality of machining points;
performing hydrogen ion implantation at each processing point of each processing path to form at least one hydrogen ion implantation layer arranged in a vertical direction;
and scanning the hydrogen ion implantation layer along each processing path according to the distribution of the plurality of processing points by adopting laser beams so as to realize the stripping of the silicon carbide wafer.
2. The method of claim 1, wherein scanning the topmost hydrogen ion implanted layer with a laser beam sequentially along each processing site of each processing path to effect exfoliation of the silicon carbide wafer comprises:
and scanning for multiple times along one processing path according to the distribution of the plurality of processing point positions, and starting scanning of the next processing path after the scanning is finished.
3. The method of claim 2, wherein the laser beam is polarized perpendicular to the direction of silicon carbide crystal growth during each scan after the first scan such that the crack propagation direction is at a 4 ° angle to horizontal.
4. A method according to claim 2, characterized in that the number of scans along a machining path according to the distribution of machining points is 3-5 times.
5. The method of claim 1, wherein performing a hydrogen ion implant at each process site of each process path comprises:
the dosage of hydrogen ions implanted into the single hydrogen ion implantation layer at each processing point of each processing path is 5 × 10 16 /cm 2 To 1 × 10 17 /cm 2 。
6. The method of claim 1, wherein the spacing between two adjacent processing paths is 20-40 μm.
7. The method of claim 1, wherein the laser beam has a pulse width of 5ns to 50ns while scanning the laser beam to a predetermined depth for each processing point of each processing path.
8. The method of claim 1, wherein performing hydrogen ion implantation at each processing site of each processing path to form at least one hydrogen ion implanted layer arranged in a vertical direction comprises:
the hydrogen ion implantation of the depth corresponding to each hydrogen ion implantation layer is sequentially completed upwards from the depth corresponding to the hydrogen ion implantation layer at the bottommost layer, wherein the hydrogen ion implantation performed at the depth corresponding to each hydrogen ion implantation layer comprises the following steps: hydrogen ion implantation is performed to each process site of each process path.
9. The method of claim 1, wherein scanning the hydrogen ion implanted layer with a laser beam along each processing path according to a distribution of a plurality of processing sites to effect exfoliation of the silicon carbide wafer comprises:
and sequentially finishing the laser beam scanning of each hydrogen ion implantation layer downwards by the topmost hydrogen ion implantation layer, wherein the laser beam scanning of each hydrogen ion implantation layer comprises the following steps: and scanning the laser beams along each processing path according to the distribution of the processing points.
10. A method as set forth in claim 9 wherein after each completion of the scanning of the hydrogen ion implanted layer, a portion of the silicon carbide ingot above the hydrogen ion implanted layer on which the scanning was completed is sliced off, and after the slicing is completed, the surface of the remaining portion of the silicon carbide ingot is subjected to the flattening treatment.
CN202211322496.5A 2022-10-26 2022-10-26 Silicon carbide cutting method Pending CN115502586A (en)

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CN202211322496.5A CN115502586A (en) 2022-10-26 2022-10-26 Silicon carbide cutting method

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Application Number Priority Date Filing Date Title
CN202211322496.5A CN115502586A (en) 2022-10-26 2022-10-26 Silicon carbide cutting method

Publications (1)

Publication Number Publication Date
CN115502586A true CN115502586A (en) 2022-12-23

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