A method and system for stripping silicon carbide ingots
By forming a modified layer inside a silicon carbide ingot and using vapor phase etching for stripping, the problems of high damage and high equipment cost in laser hidden cutting processes are solved, achieving low-damage and high-efficiency stripping results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANXI SEMICORE CRYSTAL CO LTD
- Filing Date
- 2025-06-28
- Publication Date
- 2026-05-26
AI Technical Summary
Existing silicon carbide laser lithography processes suffer from problems such as significant damage in the laser incident direction, cumbersome crystal separation processes, and high laser equipment costs.
A slightly split modified layer is formed inside a silicon carbide ingot using an ultrashort pulse laser, and the layer is then stripped by vapor phase etching using a focused nozzle to spray plasma gas, thus reducing laser damage.
It achieves low damage, simplifies the process, improves peeling efficiency and yield, and reduces equipment costs.
Smart Images
Figure CN120715448B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of crystal processing technology, and in particular to a method and system for stripping silicon carbide ingots. Background Technology
[0002] Silicon carbide (SiC) materials, with their excellent physical properties such as large bandgap, high critical breakdown field strength, and high thermal conductivity, have become the core material for the fabrication of high-temperature, high-frequency, and high-power electronic devices and optoelectronic integrated devices, and have irreplaceable application value in strategic fields such as aerospace, radar communication, and new energy. However, the high hardness of SiC crystals (Mohs hardness of 9.2-9.5, second only to diamond) makes them extremely difficult to process. Traditional machining methods such as slurry cutting and diamond wire sawing suffer from prominent problems such as high material loss rate and low cutting efficiency.
[0003] Laser stealth cutting technology achieves non-contact separation by focusing a laser on the interior of a crystal to form a modified layer, and is regarded by the industry as a key technology to break through the bottleneck of SiC processing. Currently, invention patent CN201910898954.1 discloses a single-pulse femtosecond laser cutting method for silicon carbide, which achieves cutting by destroying the crystal structure through multiphoton absorption. However, it relies on high single-pulse energy, resulting in high cost of laser equipment. Moreover, the thickness of the damaged layer after cutting is about 100μm, and large mechanical stress needs to be applied during peeling, which can easily cause substrate breakage. Invention patent JP2018159320 uses dual-beam laser processing. The first laser beam forms a modified layer, and the second laser beam suppresses longitudinal damage. Although it reduces the thickness of the damaged layer, it still requires complex optical path design and high equipment complexity. The German Siltectra "cold cutting" technology achieves separation by applying polymer cooling and contraction stress after laser modification. Although it does not require external stretching, it requires an additional liquid nitrogen cooling step, which prolongs the process and increases energy consumption. Invention patent publication number 202210238596.3 proposes high-temperature heating and quenching treatment after laser modification, which uses thermal expansion and contraction stress to assist peeling. Although it reduces the peeling force, it introduces high-temperature heating and quenching steps, and the process cycle is as long as several hours, resulting in low efficiency.
[0004] Therefore, in view of the shortcomings of existing technologies such as "high damage, complex process and high cost", this invention proposes a laser-modified layer and vapor phase etching synergistic stripping process. Summary of the Invention
[0005] The purpose of this invention is to provide a method and system for stripping silicon carbide ingots, aiming to solve the problems of large damage in the laser incident direction, cumbersome crystal separation process and high cost of laser equipment in the existing silicon carbide laser slicing process.
[0006] On the one hand, the present invention provides a method for stripping silicon carbide ingots, which adopts the following technical solution:
[0007] A method for stripping silicon carbide ingots includes the following steps:
[0008] S1. Fix the surface-polished silicon carbide ingot on the stage, and use an ultra-short pulse laser to form a slightly split modified layer inside the silicon carbide ingot. Modified layer channels are formed inside the silicon carbide ingot, and lightly split regions are formed between adjacent paths.
[0009] The crack width of the modified layer is 50-500 nm, the crack depth of a single layer is 1-10 μm, and the thickness of the damaged layer is 0.5-10 μm.
[0010] S2. The silicon carbide ingot processed in step S1 is placed upright on a base with a suction function. The modified layer channel inside the silicon carbide ingot is connected to the suction hole of the base. Plasma gas is sprayed from the modified layer channel at the edge of the silicon carbide ingot using a focusing nozzle.
[0011] S3. After the side of the silicon carbide ingot moves relative to the focusing nozzle for several revolutions, a substrate and target ingot with low surface damage are obtained.
[0012] Preferably, the path of the ultrashort pulse laser in step S1 is a round-trip path.
[0013] Preferably, the ultrashort pulse laser processing in step S1 begins from the C-side of the silicon carbide ingot.
[0014] Preferably, in step S2, the pressure at the top of the modified layer channel inside the silicon carbide ingot is greater than the pressure at the bottom, and the plasma gas flows from top to bottom along the modified layer channel and is discharged from the suction hole of the base.
[0015] Preferably, in step S2, the axis of the focusing nozzle forms an angle of 5-45° with the normal of the side of the silicon carbide ingot, so that the plasma gas flow is directed into the entrance of the modified layer channel. The flow rate of the etching gas is 0.1-2 L / min. When the focusing nozzle moves relative to the ingot, the flow rate is adjusted synchronously to keep the incident angle constant.
[0016] Preferably, the plasma gas in step S2 is any one of SF6, CF4, O2, and Ar.
[0017] On the other hand, the present invention also provides a system for laser stripping silicon carbide ingots.
[0018] A system for laser ablation of silicon carbide ingots, comprising,
[0019] The laser processing unit includes a laser generator, an optical path design unit, and a laser processing unit. The laser generator is used to emit ultrashort pulse lasers, the optical path design unit is used to focus the laser onto the interior of a silicon carbide ingot, and the laser processing unit is used for reciprocating path scanning.
[0020] The etching and stripping unit includes a base, a focusing nozzle, and a gas supply system. The base has an air intake hole, and the focusing nozzle is connected to the gas supply system. The focusing nozzle is used to spray plasma gas.
[0021] Preferably, the focusing nozzle is used to spray any one of the plasma gases SF6, CF4, O2, and Ar.
[0022] In summary, the present invention has the following beneficial technical effects:
[0023] 1. This invention uses an ultrashort pulse laser to form a slightly split modified layer on a silicon carbide ingot, and then uses a focused nozzle to complete the final peeling by vapor phase etching, thereby obtaining an ingot and substrate with low surface damage.
[0024] 2. Laser modification and etching stripping methods can reduce the process difficulty of simple laser stripping, and improve stripping yield, stripping efficiency and energy consumption. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the principle of a laser-based silicon carbide ingot stripping system in this invention;
[0026] Figure 2 This is a schematic diagram of the ultrashort pulse laser processing in this invention;
[0027] Figure 3 This is a schematic diagram illustrating the principle of ion gas etching in this invention.
[0028] Explanation of reference numerals in the attached drawings: 1. Laser generator; 2. Optical path design unit; 3. Laser processing unit; 4. Stage; 5. Base; 51. Suction port; 6. Focusing nozzle; 7. Gas supply system; 8. Silicon carbide ingot; 81. C-surface; 82. Modified layer channel. Detailed Implementation
[0029] The following is in conjunction with the appendix Figure 1-3 The present invention will be further described in detail with reference to the embodiments.
[0030] Example
[0031] Example 1
[0032] Reference Figure 1 and Figure 2A system for laser-induced stripping of silicon carbide ingots includes a laser processing unit and an etching and stripping unit. The laser processing unit includes a laser generator 1, an optical path design unit 2, and a laser processing unit 3. A stage 4 is placed below the laser processing unit 3, and the stage 4 is horizontally positioned to ensure that the C / SI surface of the silicon carbide is horizontal when the laser scans it. The silicon carbide ingot 8 to be processed is fixedly placed on the stage 4. The laser generator 1 emits an ultrashort pulse laser, and the optical path design unit 2 focuses the ultrashort pulse laser onto the interior of the silicon carbide ingot 8. The laser output from the laser processing unit 3 scans the silicon carbide ingot 8 along a reciprocating path to form a modified layer channel 82 inside the silicon carbide ingot 8.
[0033] Reference Figure 3 The etching and stripping unit includes a base 5, a focusing nozzle 6, and a gas supply system 7. The base 5 is arc-shaped. After the silicon carbide ingot is placed vertically, it is embedded in the semi-arc base 5. The base 5 has a suction hole 51, which continuously draws air to place the silicon carbide ingot 8, which forms the modified layer channel 82, vertically on the base 5. The suction hole 51 is connected to the modified layer channel 82. The focusing nozzle 6 is connected to the gas supply system 7. The gas supply system 7 is used to provide any one of the plasma gases SF6, CF4, O2, and Ar. The focusing nozzle 6 is used to spray plasma gas into the modified layer channel 82 at the edge of the silicon carbide ingot 8.
[0034] Example 2
[0035] A method for stripping silicon carbide ingots includes the following steps:
[0036] 1) Fix the surface-polished silicon carbide ingot 8 on the stage 4 (the stage is placed horizontally to ensure that the C / SI surface of the silicon carbide is horizontal when the laser scan is performed). Use an ultrashort pulse laser with a reciprocating path to start from the C surface 81 of the silicon carbide ingot 8 and form a slightly split modified layer inside the silicon carbide ingot 8. A modified layer channel 82 is formed inside the silicon carbide ingot 8, and a lightly split region is formed between adjacent paths.
[0037] After treatment with ultrashort pulse laser, the crack width of the slightly split modified layer is 50-500 nm, the crack depth of a single layer is 1-10 μm, and the thickness of the damaged layer is 0.5-10 μm.
[0038] 2) The silicon carbide ingot 8 processed in step 1) is placed vertically on a base 5 with a suction function. The modified layer channel 82 inside the silicon carbide ingot 8 is connected to the suction hole 51 of the base 5. A cluster nozzle 6 is used to spray any one of the plasma gases SF6, CF4, O2, and Ar from the modified layer channel 82 at the edge of the silicon carbide ingot 8. The cluster nozzle 6 is connected to the upper part of the modified layer channel 82 of the silicon carbide ingot 8. The suction hole 51 of the base 5 forms a negative pressure, that is, the pressure at the upper part of the modified layer channel 82 is greater than the pressure at the lower part. Under the action of the pressure difference, the plasma gas flows from the upper part to the lower part along the modified layer channel 82. During the flow, the plasma gas reacts with the modified layer and the damaged layer material of the light splitting zone. The reaction products are discharged by the suction hole 51 of the base 5 with the gas flow.
[0039] The axis of the focusing nozzle forms an angle of 5-45° with the normal of the side of the silicon carbide ingot, so that the plasma gas flow is directed into the entrance of the modified layer channel. The flow rate of the etching gas is 0.1-2L / min. When the nozzle moves relative to the ingot (circular scanning), the flow rate needs to be adjusted synchronously to keep the incident angle constant and prevent the gas flow from leaving the channel entrance.
[0040] 3) After the side of the silicon carbide ingot 8 moves relative to the beam nozzle 6 for several revolutions, a substrate and target ingot with low surface damage are obtained.
[0041] Performance testing
[0042] Silicon carbide ingots were peeled off using conventional slurry cutting, conventional laser cutting, and the process described in Example 2 of this invention, respectively. The crack width, damaged layer thickness, surface roughness, and substrate fracture rate were measured for each process. The test results are shown in Table 1.
[0043] Table 1 Comparison of damage effects between traditional mortar cutting, traditional laser cutting, and Example 2 of the present invention.
[0044] index Traditional mortar cutting Traditional laser peeling This invention Crack width none 1.8±0.5μm 220±30nm Damage layer thickness 95±25μm 45±15μm 2±1.5μm Surface roughness 2.8μm 1.5μm 0.42μm Substrate fracture rate 3 / 20(15％) 4 / 20(20％) 0 / 20(0％)
[0045] As shown in Table 1, the effect of traditional laser ablation is better than that of traditional slurry cutting. The process effect of the embodiment of the present invention is significantly better than that of traditional laser ablation, with better crack width, damage layer thickness, surface roughness and substrate breakage rate.
[0046] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A method for stripping silicon carbide ingots, characterized in that, Includes the following steps: S1. Fix the surface-polished silicon carbide ingot on the stage. Using an ultra-short pulse laser, starting from the C-side of the silicon carbide ingot, a slightly split modified layer is formed inside the silicon carbide ingot along a reciprocating path. Modified layer channels are formed inside the silicon carbide ingot, and lightly split regions are formed between adjacent paths. The crack width of the modified layer is 50-500 nm, the crack depth of a single layer is 1-10 μm, and the thickness of the damaged layer is 0.5-10 μm. S2. The silicon carbide ingot processed in step S1 is placed upright on a base with a suction function. The modified layer channel inside the silicon carbide ingot is connected to the suction hole of the base. The pressure at the top of the modified layer channel is greater than the pressure at the bottom. The plasma gas flows from top to bottom along the modified layer channel and is discharged from the suction hole of the base. The plasma gas is sprayed from the modified layer channel at the edge of the silicon carbide ingot using a focusing nozzle. S3. After the side of the silicon carbide ingot moves relative to the focusing nozzle for several revolutions, a substrate and target ingot with low surface damage are obtained.
2. The method for stripping silicon carbide ingots according to claim 1, characterized in that, In step S2, the axis of the focusing nozzle forms an angle of 5–45° with the normal of the side of the silicon carbide ingot, so that the plasma gas flow is directed into the entrance of the modified layer channel. The flow rate of the etching gas is 0.1–2 L / min. When the focusing nozzle moves relative to the ingot, the flow rate is adjusted synchronously to keep the incident angle constant.
3. The method for stripping silicon carbide ingots according to claim 2, characterized in that, The plasma gas in step S2 is any one of SF6, CF4, O2, and Ar.
4. A system for laser lift-off of silicon carbide ingots using the method described in any one of claims 1-3, characterized in that, include, The laser processing unit includes a laser generator (1), an optical path design unit (2), and a laser processing unit (3). The laser generator (1) is used to emit ultrashort pulse lasers, the optical path design unit (2) is used to focus the ultrashort pulse lasers inside the silicon carbide ingot (8), and the laser processing unit (3) is used for reciprocating path scanning. The etching and stripping unit includes a base (5), a focusing nozzle (6) and a gas supply system (7). The base (5) has an air intake hole (51). The focusing nozzle (6) is connected to the gas supply system (7) and is used to spray plasma gas.
5. The system for stripping silicon carbide ingots according to claim 4, characterized in that, The focusing nozzle (6) is used to spray any one of the plasma gases SF6, CF4, O2, and Ar.