A method and system for processing silicon carbide based on the synergistic effect of plasma and laser
By forming a modified layer through plasma pretreatment and working in synergy with laser, the problems of large heat-affected zone, uneven modified layer and difficulty in controlling microcracks in silicon carbide processing have been solved, achieving low thermal damage and high efficiency in silicon carbide processing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INST OF LASER MFG HENAN ACAD OF SCI
- Filing Date
- 2026-04-14
- Publication Date
- 2026-06-12
AI Technical Summary
Existing technologies in silicon carbide processing suffer from problems such as large heat-affected zones, uneven modified layers, difficulty in controlling microcracks, and easy surface chipping. Furthermore, traditional methods have failed to effectively reduce thermal damage and lack synergistic control of plasma and laser.
A modified layer of 0.5~3μm thickness is formed by plasma pretreatment. By utilizing the synergistic effect of plasma and laser, the scanning path is controlled to overlap, the laser energy threshold is reduced, and silicon carbide processing with low thermal damage is achieved.
It significantly reduces the energy requirement for laser processing, improves the uniformity and continuity of the modified layer, reduces thermal damage, and improves processing accuracy and efficiency, making it suitable for silicon carbide wafers and ingots of different sizes and thicknesses.
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Figure CN122184607A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor material processing technology, and in particular to a silicon carbide processing method and system based on the synergistic effect of plasma and laser. Background Technology
[0002] Silicon carbide (SiC), as a typical wide-bandgap semiconductor material, has become a core substrate in the field of power semiconductor device manufacturing due to its excellent properties such as high breakdown electric field, high thermal conductivity, and high-temperature stability. As the size of silicon carbide wafers continues to increase and the integration of devices continues to improve, the industry's requirements for wafer cutting quality and surface integrity are becoming increasingly stringent. Currently, silicon carbide wafer processing mainly includes mechanical wheel cutting, abrasive wheel scribing, and laser cutting. Among them, laser stealth cutting technology achieves separation by forming a modified layer inside the material and combining it with mechanical stress. It has the advantages of fast processing speed, no tool wear, and adaptability to hard and brittle materials, making it the mainstream technology for silicon carbide processing. However, due to the material characteristics of silicon carbide, such as high hardness and brittleness, low absorption rate at specific wavelengths, high thermal conductivity, and high melting point, laser processing still has technical pain points such as local heat accumulation leading to a large heat-affected zone, uneven width of the modified layer and difficulty in controlling the crack propagation direction, easy generation of microcracks and edge chipping on the surface and edges, and the need for high energy density lasers due to the high modification threshold.
[0003] Existing technologies address the aforementioned problems by improving processing results through increasing laser power and optimizing laser pulse parameters, or by employing auxiliary gas cooling or simple plasma treatment to reduce thermal damage. However, these improvements have significant limitations: the former only adjusts laser process parameters and does not control the processing threshold from the perspective of the silicon carbide material itself, making it difficult to ensure the continuity of the modified layer while reducing thermal damage; the latter are mostly independent process steps and do not form an effective synergistic control mechanism with laser processing, especially lacking precise control over the duration of the material's activated state after plasma treatment and the synergistic time window between plasma and laser processing, thus failing to achieve low-thermal-damage, high-quality silicon carbide processing. Therefore, how to reduce the laser processing threshold by altering the local physicochemical state of the silicon carbide material without increasing laser energy, and complete laser processing within a specific time window to achieve low-thermal-damage results, has become a key technical problem urgently needing to be solved in this field. Summary of the Invention
[0004] The problem solved by this invention is: how to utilize the time-dependent pre-activation of plasma to achieve low thermal damage laser processing of silicon carbide within a specific time period.
[0005] To address the above problems, embodiments of the present invention provide a silicon carbide processing method based on the synergistic effect of plasma and laser, the processing method comprising the following steps:
[0006] S1. Plasma is used to pretreat the silicon carbide area to be processed, so that the surface layer of the area to be processed enters an activated state and forms a surface modification layer.
[0007] Furthermore, the power density of the plasma is controlled to be 0.5~5 W / mm². 2 .
[0008] Furthermore, the single-point processing time of the plasma on the silicon carbide region to be processed is 1~50ms.
[0009] Furthermore, the plasma is atmospheric pressure jet plasma or capacitively coupled plasma.
[0010] Furthermore, the thickness of the surface modification layer is 0.5~3 μm.
[0011] This invention activates the silicon carbide surface through plasma pretreatment, forming a modified layer with a thickness of 0.5~3μm, which significantly reduces the energy threshold required for laser processing and also improves the uniformity and continuity of the modified layer.
[0012] S2. Within the time window after the plasma pretreatment is completed, the area to be processed is scanned and processed using a laser;
[0013] Furthermore, in step S2, the time window is 0.5~10 ms.
[0014] S3. A modified layer is formed on the silicon carbide by laser action;
[0015] S4. Achieve low thermal damage separation or surface modification treatment of the silicon carbide.
[0016] Furthermore, the scanning path during plasma pretreatment partially or completely overlaps with the scanning path during laser processing.
[0017] This invention further enhances processing accuracy and efficiency by coordinating the scanning paths of plasma and laser.
[0018] Furthermore, the processing energy of the laser is 70% to 90% of the processing energy under plasma-free pretreatment conditions.
[0019] Furthermore, the laser is a picosecond pulse laser or a femtosecond pulse laser.
[0020] Furthermore, the processing method is the surface modification method for silicon carbide.
[0021] Furthermore, the processing method is the stealth cutting method for silicon carbide.
[0022] Furthermore, the silicon carbide specifications adapted to the method include 4H-SiC single crystal wafers, 6H-SiC single crystal wafers, 2-8 inch silicon carbide wafers, 200-800μm thick silicon carbide wafers, and silicon carbide ingots.
[0023] In one embodiment of the present invention, a silicon carbide processing system based on the synergistic effect of plasma and laser is also provided. The silicon carbide processing method based on the synergistic effect of plasma and laser described in the above embodiment is applied to the processing system. The processing system includes: a laser for generating the laser.
[0024] Plasma generator, used to produce plasma jets;
[0025] A coaxial output structure is used to adjust the optical axis of the laser and the output direction of the plasma jet to be radially coaxial, so that their scanning paths completely coincide and their focal planes match.
[0026] Motion platform for supporting and moving the silicon carbide;
[0027] A controller is configured to control the plasma generator to pre-process the silicon carbide region to be processed, and to control the laser to scan and process the same region within a time window after the pre-processing is completed, and to control the output energy of the laser to be lower than the processing energy under conditions without plasma pre-processing.
[0028] The beneficial effects of the present invention include at least the following:
[0029] (1) It achieves precise synergy between plasma and laser processing. By controlling the time window after plasma pretreatment, the activation state of silicon carbide surface is fully utilized to reduce the laser processing threshold. Under the premise of reducing laser energy by 70%~90%, a continuous and uniform modified layer can still be formed, which effectively solves the technical pain points of large heat-affected zone and high modification threshold in traditional laser processing.
[0030] (2) The 0.5~3μm surface modification layer formed by plasma pretreatment not only optimizes the absorption efficiency of silicon carbide to laser, but also suppresses the generation of microcracks and edge breakage during processing, greatly improving the integrity of the processed surface.
[0031] (3) The coaxial output structure and intelligent controller configured in the processing system can realize coaxial confocal control of plasma jet and laser beam, as well as precise matching of scanning path. This not only simplifies the operation process, but also adapts to silicon carbide wafers and ingots of different sizes from 2 to 8 inches and different thicknesses from 200 to 800 μm, and has stronger process compatibility and scenario adaptability. Attached Figure Description
[0032] Figure 1 This is a flowchart of a silicon carbide processing method based on the synergistic effect of plasma and laser according to the present invention;
[0033] Figure 2 A schematic diagram of the time window provided for this invention;
[0034] Figure 3 This is a schematic diagram of a silicon carbide processing system based on the synergistic effect of plasma and laser according to the present invention.
[0035] Explanation of reference numerals in the attached figures:
[0036] 1-Laser; 2-Beam shaping assembly; 3-Plasma generator; 4-Coaxial output structure; 5-Plasma jet; 6-Silicon carbide wafer; 7-Motion platform. Detailed Implementation
[0037] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.
[0038] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0039] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0040] First embodiment: Wafer stealth dicing
[0041] The system used in this embodiment includes:
[0042] Femtosecond pulsed laser: Wavelength: 1064 nm; Pulse width: 400 fs; Repetition rate: 200 kHz.
[0043] Atmospheric pressure jet plasma generator: Gas: Ar; Power: 30 W; Gas flow rate: 8 L / min.
[0044] Three-axis motion platform: The plasma nozzle and the laser optical axis are arranged coaxially, and their focal points are in the same position.
[0045] See Figure 1 and Figure 2 In this embodiment, the thickness is 500 μm and the crystal orientation is <0001> The 4H-SiC single crystal wafers were processed using a plasma pre-activation assisted stealth dicing method, with the specific steps as follows:
[0046] S1. Plasma pretreatment: An atmospheric pressure jet plasma generator is used, with a plasma power density set to 0.5 W / mm². 2 The scanning speed is 100 mm / s, and single-point preprocessing is performed on the wafer dicing area to be processed, with a single-point processing time of 1 ms.
[0047] S2. Laser scanning within the window: Within a 0.5 ms time window after the plasma pretreatment is completed, the picosecond pulse laser is activated, and the laser processing energy is set to 70% of the traditional processing energy. The laser scanning path is completely overlapped with the plasma pretreatment path, and a continuous and uniform modified layer is formed inside the wafer at a scanning speed of 100 mm / s.
[0048] S3. Dicing process: The laser-processed wafer is placed on a precision dicing stage, and uniform mechanical stress is applied to precisely separate the wafer along the modified layer to meet the subsequent packaging requirements of power semiconductor devices.
[0049] Second Embodiment
[0050] The system used in this embodiment includes:
[0051] Femtosecond pulsed laser: Wavelength: 1064 nm; Pulse width: 400 fs; Repetition rate: 200 kHz.
[0052] Atmospheric pressure jet plasma generator: Gas: Ar; Power: 30 W; Gas flow rate: 8 L / min.
[0053] Three-axis motion platform: The plasma nozzle and the laser optical axis are arranged coaxially, and their focal points are in the same position.
[0054] In this embodiment, the thickness is 500 μm and the crystal orientation is <0001> The 4H-SiC single crystal wafers were processed using a plasma pre-activation assisted stealth dicing method, with the specific steps as follows:
[0055] S1. Plasma pretreatment: An atmospheric pressure jet plasma generator is used, with a plasma power density of 3 W / mm². 2 The scanning speed is 100 mm / s, and single-point preprocessing is performed on the wafer dicing area to be processed, with a single-point processing time of 25 ms.
[0056] S2. Laser scanning within the window: Within a 5 ms time window after the plasma pretreatment is completed, the picosecond pulse laser is activated, and the laser processing energy is set to 80% of the traditional processing energy. The laser scanning path is completely overlapped with the plasma pretreatment path, and a continuous and uniform modified layer is formed inside the wafer at a scanning speed of 100 mm / s.
[0057] S3. Dicing process: The laser-processed wafer is placed on a precision dicing stage, and uniform mechanical stress is applied to precisely separate the wafer along the modified layer to meet the subsequent packaging requirements of power semiconductor devices.
[0058] Third Embodiment
[0059] The system used in this embodiment includes:
[0060] Femtosecond pulsed laser: Wavelength: 1064 nm; Pulse width: 400 fs; Repetition rate: 200 kHz.
[0061] Atmospheric pressure jet plasma generator: Gas: Ar; Power: 30 W; Gas flow rate: 8 L / min.
[0062] Three-axis motion platform: The plasma nozzle and the laser optical axis are arranged coaxially, and their focal points are in the same position.
[0063] In this embodiment, the thickness is 500 μm and the crystal orientation is <0001> The 4H-SiC single crystal wafers were processed using a plasma pre-activation assisted stealth dicing method, with the specific steps as follows:
[0064] S1. Plasma pretreatment: An atmospheric pressure jet plasma generator is used, with a plasma power density of 5 W / mm². 2 The scanning speed is 100 mm / s, and single-point preprocessing is performed on the wafer dicing area to be processed, with a single-point processing time of 50 ms.
[0065] S2. Laser scanning within the window: Within a 10 ms time window after the plasma pretreatment is completed, the picosecond pulse laser is activated, and the laser processing energy is set to 90% of the traditional processing energy. The laser scanning path is completely overlapped with the plasma pretreatment path, and a continuous and uniform modified layer is formed inside the wafer at a scanning speed of 100 mm / s.
[0066] S3. Dicing process: The laser-processed wafer is placed on a precision dicing stage, and uniform mechanical stress is applied to precisely separate the wafer along the modified layer to meet the subsequent packaging requirements of power semiconductor devices.
[0067] Fourth embodiment
[0068] The system used in this embodiment includes:
[0069] Femtosecond pulsed laser: Wavelength: 1064 nm; Pulse width: 400 fs; Repetition rate: 200 kHz.
[0070] Atmospheric pressure jet plasma generator: Gas: Ar; Power: 30 W; Gas flow rate: 8 L / min.
[0071] Three-axis motion platform: The plasma nozzle and the laser optical axis are arranged coaxially, and their focal points are in the same position.
[0072] In this embodiment, the thickness is 500 μm and the crystal orientation is <0001> The 4H-SiC single crystal wafers were processed using a plasma pre-activation assisted stealth dicing method, with the specific steps as follows:
[0073] S1. Plasma pretreatment: An atmospheric pressure jet plasma generator is used, with a plasma power density of 2 W / mm². 2 The scanning speed is 100 mm / s, and single-point preprocessing is performed on the wafer dicing area to be processed, with a single-point processing time of 5 ms.
[0074] S2. In-window laser scanning: Within a 2 ms time window after the plasma pretreatment is completed, the picosecond pulse laser is activated, and the laser processing energy is set to 70% of the traditional processing energy. The laser scanning path is completely overlapped with the plasma pretreatment path, and a continuous and uniform modified layer is formed inside the wafer at a scanning speed of 100 mm / s.
[0075] S3. Dicing process: The laser-processed wafer is placed on a precision dicing stage, and uniform mechanical stress is applied to precisely separate the wafer along the modified layer to meet the subsequent packaging requirements of power semiconductor devices.
[0076] Fifth embodiment: Silicon carbide surface modification
[0077] Compared to the first embodiment, this embodiment targets SiC devices that require improved surface hydrophilicity and bonding performance. It utilizes the synergistic effects of plasma and laser to perform silicon carbide surface modification processing. The specific steps are as follows:
[0078] S1. Plasma pretreatment: An atmospheric pressure jet plasma generator is used, with a plasma power density of 1 W / mm². 2The scanning speed was 100 mm / s, scanning along the edge region of the device, with a single-point interaction time of 10 ms. Active hydrogen atoms in the plasma react with the silicon-carbon bonds on the silicon carbide surface, breaking some covalent bonds and introducing dangling bonds. Simultaneously, the bombardment by argon ions forms a nanoscale rough structure on the surface, ultimately forming a 1 μm thick activation layer rich in dangling bonds on the wafer surface, providing reaction sites for subsequent laser-induced modification.
[0079] S2. Laser scanning within the window: Within a 5 ms time window after the plasma pretreatment is completed, the picosecond pulse laser is activated, and the laser processing energy is set to 80% of the traditional processing energy. The laser scanning path is completely overlapped with the plasma pretreatment path, and a continuous and uniform modified layer is formed inside the wafer at a scanning speed of 100 mm / s.
[0080] The silicon carbide before and after modification was tested, and the results are shown in Table 1.
[0081] Table 1
[0082]
[0083] As shown in Table 1, the silicon carbide surface modification achieved by the synergistic effect of plasma and laser in this embodiment is significant: the surface contact angle is greatly reduced from 65° to 32°, and the hydrophilicity is greatly improved, providing a better surface foundation for subsequent bonding, coating and other processes; the surface microcrack density is reduced by 35% compared with the baseline, which effectively improves the problem of surface micro-damage that is easily caused by traditional modification processes and ensures the structural integrity of silicon carbide devices; the adhesion of subsequent metal deposition is improved from 4B level to 5B level, which significantly enhances the bonding stability between the metal layer and the silicon carbide surface layer, and can effectively avoid failures such as metal layer peeling and contact failure during long-term operation of the device.
[0084] Comparative Example 1
[0085] Compared to the fourth embodiment, the difference lies in the absence of plasma assistance; the laser processing energy is set to 100% of the conventional processing energy, while the remaining processing parameters are completely consistent with the first embodiment, i.e., a picosecond pulsed laser is used at a scanning speed of 100 mm / s to process a 500 μm thick material with a crystal orientation of [missing information]. <0001> The 4H-SiC single crystal wafer is scanned and processed in the dicing area, and then cleaved.
[0086] Comparative experiments show that the chipping rate of the silicon carbide wafer dicing surface after processing in the fourth embodiment is 2.9%, far lower than the 6.2% chipping rate in Comparative Example 1; the width of the heat-affected zone is controlled at 5~8 μm, while the width of the heat-affected zone in Comparative Example 1 is 8~14 μm; in addition, compared with Comparative Example 1, the crack uniformity of the silicon carbide wafer dicing surface after processing in the fourth embodiment is improved by about 28%. This is because during the plasma pretreatment stage, the bombardment of argon ions forms a uniform stress buffer layer on the surface of silicon carbide, while breaking some silicon-carbon covalent bonds, making the surface in an activated state. When the subsequent laser acts within the time window, the absorption efficiency of the activated silicon carbide for laser energy is improved to a certain extent, and the laser energy can be more accurately applied to the modified layer formation area, reducing the diffusion of energy to the surrounding area, thereby significantly reducing the range of the heat-affected zone. Simultaneously, plasma pretreatment generates minute stress concentration points in the cutting area, guiding cracks during laser processing along a predetermined path. This avoids the edge chipping problem caused by random crack propagation without plasma assistance, thus significantly reducing the edge chipping rate and greatly improving crack uniformity. Experimental results show that, while ensuring the same cutting quality, the laser energy used in this embodiment is only 70% of that of the traditional process, reducing equipment energy consumption and processing costs while significantly improving mass production efficiency. Furthermore, a 1000-hour high-temperature aging test was conducted on the cut wafers, and the fluctuation range of their electrical performance parameters was controlled within 2%, indicating that the plasma pre-activated assisted stealth cutting process did not negatively affect the intrinsic properties of silicon carbide wafers and possesses good process stability and reliability.
[0087] Comparative Example 2
[0088] Compared with the fourth embodiment, the plasma working gas was replaced with an Ar + 5% O2 mixture, the plasma power was 25 W, the scanning speed was 120 mm / s, the time window was 3 ms, and other conditions remained the same as in the fourth embodiment.
[0089] By comparing the processing results of the fourth embodiment with those of Comparative Example 2, it was found that the chipping rate of the cut surface and the width of the heat-affected zone were further reduced in Comparative Example 2. In addition, the modification threshold in Comparative Example 2 was reduced by about 20% compared with the first embodiment. This is because the oxygen atoms in the oxygen-containing mixed gas react with the silicon and carbon atoms on the surface of silicon carbide to generate oxide intermediates such as silicon dioxide and carbon monoxide, which further destroys the stability of silicon-carbon covalent bonds, making the surface activation level higher, thereby reducing the modification threshold for subsequent laser processing. This result also shows that in the process of silicon carbide processing, the type and ratio of plasma working gas can be adjusted according to different processing requirements to achieve a balance and optimization between the activation level and the surface structure stability.
[0090] Sixth Embodiment
[0091] See Figure 3 In one specific embodiment, the present invention also provides a silicon carbide processing system based on the synergistic effect of plasma and laser. The silicon carbide processing method based on the synergistic effect of plasma and laser described in the above embodiment is applied to this processing system. The processing system includes: a laser 1 for generating the laser; a plasma generator 3 for generating a plasma jet; a coaxial output structure 4 for adjusting the optical axis of the laser and the output direction of the plasma jet to be radially coaxial, so that their scanning paths completely overlap and their focal planes match; a motion platform 7 for carrying and moving the silicon carbide; and a controller configured to control the plasma generator to preprocess the area to be processed of the silicon carbide, and to control the laser to scan and process the same area within the time window after the preprocessing is completed, and to control the output energy of the laser to be lower than the processing energy under the condition of no plasma preprocessing. This processing system has all the technical features of the above processing method, which will not be described in detail here.
[0092] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
Claims
1. A silicon carbide processing method based on the synergistic effect of plasma and laser, characterized in that, The processing method includes the following steps: S1. Plasma is used to pretreat the silicon carbide area to be processed, so that the surface layer of the area to be processed enters an activated state and forms a surface modification layer. S2. Within the time window after the plasma pretreatment is completed, the area to be processed is scanned and processed using a laser; S3. A modified layer is formed on the silicon carbide by laser action; S4. Achieve low thermal damage separation or surface modification treatment of the silicon carbide.
2. The processing method according to claim 1, characterized in that, In step S1, the power density of the plasma is controlled to be 0.5~5 W / mm². 2 The plasma treatment time for a single point on the silicon carbide region to be processed is 1~50 ms.
3. The processing method according to claim 1, characterized in that, In step S1, the thickness of the surface modification layer is 0.5~3μm.
4. The processing method according to claim 1, characterized in that, In step S2, the time window is 0.5~10ms.
5. The processing method according to claim 1, characterized in that, The scanning path during plasma pretreatment partially or completely overlaps with the scanning path during laser processing.
6. The processing method according to claim 1, characterized in that, The laser processing energy is 70% to 90% of the processing energy under plasma-free pretreatment conditions.
7. The processing method according to claim 1, characterized in that, The plasma is atmospheric pressure jet plasma or capacitively coupled plasma; the laser is a picosecond pulse laser or a femtosecond pulse laser.
8. The processing method according to claim 1, characterized in that, The processing method is the surface modification method for silicon carbide.
9. The processing method according to claim 1, characterized in that, The processing method is the stealth cutting method for silicon carbide.
10. A silicon carbide processing system based on the synergistic effect of plasma and laser for implementing the processing method according to any one of claims 1 to 9, characterized in that, include: A laser for generating the laser; Plasma generator, used to produce plasma jets; A coaxial output structure is used to adjust the optical axis of the laser and the output direction of the plasma jet to be radially coaxial, so that their scanning paths completely coincide and their focal planes match. Motion platform for supporting and moving the silicon carbide; A controller is configured to control the plasma generator to pre-process the silicon carbide region to be processed, and to control the laser to scan and process the same region within a time window after the pre-processing is completed, and to control the output energy of the laser to be lower than the processing energy under conditions without plasma pre-processing.