A method for low-cost low-pressure thermal oxidation of dummy wafer with oxygen regeneration carbon film

Abstract

The application discloses a kind of low-cost low-pressure oxygen hot oxidation regeneration carbon film Dummy wafer method, belong to semiconductor Dummy wafer regeneration recycling technical field.The method includes: sorting pretreatment, low-pressure thermal oxidation carbon removal, cooling with furnace, ultrapure water cleaning and constant-temperature drying.Carbon film thickness is not greater than 5 μm of carbon film Dummy wafer, is placed into low-pressure furnace tube, chamber pressure is controlled at 1Torr, is heated to 500 DEG C and constant temperature, and 1000sccm high-purity oxygen gas is introduced and is oxidized for 30min, so that carbon film is completely oxidized into carbon dioxide gas and is separated from wafer base.The application can realize 5 μm and below carbon film 100% no residue removal under the condition of 1Torr, 500 DEG C, after regeneration wafer surface roughness Ra≤0.8nm, particle quantity≤3, no silicon base damage, wafer recycling reuse frequency is not less than 12 times, while energy consumption and mass production cost are greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor dummy wafer regeneration and recycling technology, and particularly relates to a low-cost, low-pressure oxygen-assisted thermal oxidation method for regenerating carbon film dummy wafers. Background Technology

[0002] In semiconductor manufacturing processes, amorphous carbon films are frequently used as sacrificial layers for temporary trench filling and as plasma protection layers. Residual carbon layers on the surface of spent carbon film dummy wafers and within the trenches cannot be directly reused and require regeneration processing.

[0003] Currently, the main methods for regenerating carbon film dummy wafers include the following: Plasma dry etching involves ion bombardment, which increases the roughness of the polished silicon wafer surface. Thick carbon films and residues are easily left at the bottom of trenches, resulting in incomplete removal, and the equipment costs are high. Wet chemical cleaning relies on strong oxidants to corrode the carbon film, which easily erodes the silicon substrate, causing severe lattice damage. The wafer can only be recycled 2 to 3 times, and a large amount of hazardous waste is generated. Traditional high-temperature furnace tube oxidation carbon removal processes often use 600℃ or 700℃ high-temperature conditions. Although the carbon film removal effect and wafer surface cleanliness are superior under high-temperature conditions, the furnace tube heating energy consumption is high, the equipment has large high-temperature heat loss, and the overall cost of mass production remains high. Furthermore, the wafer has multiple material structures before and after high-temperature treatment, which can easily induce thermal stress deformation and lattice damage due to differences in thermal expansion coefficients.

[0004] Existing heat treatment technologies only involve cavity cleaning and conventional wafer annealing processes. There is no specific process solution for the regeneration of carbon film dummy wafers, nor is there a precise process window with 1 Torr pressure, 500°C constant temperature, and fixed oxidation time. Furthermore, no optimal working conditions that balance regeneration quality and mass production economy have been selected through multiple sets of gradient control experiments. Summary of the Invention

[0005] This invention provides a method for regenerating carbon film dummy wafers through low-pressure oxygen-assisted thermal oxidation, comprising the following steps: sorting and pretreatment, selecting carbon film dummy wafers with a carbon film thickness of no more than 5 μm, free from edge chipping, cracks, and heavy metal contamination, and removing large foreign objects, floating dust, and loose impurities from the surface; placing the pretreated wafers into a low-pressure furnace tube, sealing the furnace body and stabilizing the chamber pressure at 1 Torr, heating and maintaining a constant temperature of 500°C, continuously introducing 1000 sccm of high-purity oxygen, and performing constant-temperature oxidation treatment for 30 minutes to completely oxidize the carbon film on the wafer surface and in the trenches into carbon dioxide gas that detaches from the wafer substrate; stopping heating and oxygen supply, allowing the wafer to cool naturally to room temperature in the sealed furnace; removing the cooled wafer, rinsing the front, back, and trench structures of the wafer with semiconductor standard ultrapure water, and then drying and removing water using a semiconductor standard constant-temperature drying process.

[0006] Furthermore, under standard operating conditions of 1 Torr and 500℃, the carbon film etching rate stably reaches 290–308 nm / min, the on-wafer etching uniformity is ≤1.40%, the surface roughness Ra of the regenerated wafer is ≤0.8 nm, and the number of surface particles is ≤3.

[0007] Furthermore, gradient temperature tests have verified that the process temperature is positively correlated with the carbon film etching rate, surface cleanliness, and surface roughness. The recycling performance is better at high temperatures of 600℃ and 700℃, but this invention prefers the low temperature condition of 500℃ to maximize the benefits of mass production with lower energy consumption and lower equipment wear.

[0008] Furthermore, when the carbon film thickness exceeds 5 μm, the film layer is not completely removed. Therefore, the thickness of the incoming carbon film is strictly limited to no more than 5 μm.

[0009] Furthermore, the oxidation process involves only gas-phase oxidation reactions, without ion bombardment or chemical corrosion, resulting in no thickness loss or lattice micro-damage to the silicon substrate, and the wafer can be recycled at least 12 times.

[0010] Furthermore, this method is applicable to the regeneration of dummy wafers with planar carbon films and carbon films embedded in large-aperture trenches, with no carbon residue inside the trenches.

[0011] Furthermore, after the carbon film is completely removed, the wafer has a pure silicon homogeneous structure, which in principle completely eliminates the risk of thermal stress deformation and lattice damage.

[0012] Furthermore, a small amount of SiO thin layer is generated on the surface of the silicon substrate during the process, which can achieve differentiated adaptation treatment; when the wafer is repeatedly deposited with carbon film, the SiO thin layer is directly retained without affecting the subsequent carbon film preparation and performance; when applied to other high-precision processes, after the high-temperature oxidation process is completed, NF3 gas is introduced for constant temperature treatment for 10 minutes to completely remove the SiO layer and reduce the high-purity silicon substrate.

[0013] Furthermore, under a constant temperature of 500℃, gradient tests were conducted with chamber pressures set to 0.2 Torr, 0.6 Torr, 1 Torr, 1.5 Torr, and 2 Torr, respectively. Under the 1 Torr condition, the etching rate was 308 nm / min, the on-chip etching uniformity was 1.20%, the number of surface particles was 0, and the surface roughness was 0.7 nm. These were the optimal pressure parameters that balanced etching rate, on-chip uniformity, surface particles, and surface roughness.

[0014] Furthermore, under the process conditions of 1 Torr, 500℃, and oxidation for 30 min, removal verification was performed on carbon films with thicknesses of 50 nm, 500 nm, and 5 μm. All three films achieved residue-free removal, with surface particle counts of 2, 1, and 3 particles, respectively. Removal verification was performed on an 8 μm thick carbon film, resulting in a small amount of residue with 58 surface particles. When this number exceeds the carbon film thickness limit, complete film removal and wafer cleanliness cannot be guaranteed.

[0015] The present invention has the following beneficial effects.

[0016] First, it features a unique approach to balancing operating conditions. This invention fully verifies the performance advantages of high-temperature processes through multiple sets of gradient control experiments. However, it is not limited to the industry's conventional high-temperature film removal thinking. Instead, it creatively balances the core contradiction between process performance and mass production costs. Under the premise of fully meeting the requirements of non-destructive, residue-free, and high-cleanliness regeneration in mass production, it abandons redundant high-temperature performance and selects a low-temperature, low-cost operating condition of 500℃, thus achieving the optimal balance between technical effects and mass production benefits.

[0017] Secondly, it exhibits excellent process performance and strong mass production stability. A 1 Torr, 500℃ coupling window is optimally selected, resulting in high etching rates, good uniformity, and extremely low surface particle size and roughness. The 5μm carbon film thickness boundary is strictly limited, achieving 100% film removal in 30 minutes, with stable batch yield.

[0018] Third, it achieves extreme cost reduction and outstanding economic efficiency in mass production. Compared with the 600℃ and 700℃ high-temperature oxidation processes, the 500℃ low-temperature operating condition significantly reduces furnace tube heating energy consumption, reduces high-temperature heat loss of equipment and operation and maintenance costs, and maximizes the reduction of mass production costs while meeting the recycling quality standards.

[0019] Fourth, the entire process is non-destructive, significantly extending wafer lifespan. There is no plasma bombardment or chemical corrosion; only a vapor-phase oxidation reaction occurs. The silicon polished surface suffers no lattice damage or thickness loss, allowing for far more wafer recycling cycles than traditional processes.

[0020] Fifth, the process boasts strong stability and wide applicability. It employs a standardized closed-loop cleanroom process, eliminating ion bombardment and chemical corrosion throughout, ensuring zero damage to the wafer substrate from the outset. After carbon film removal, the wafer is a pure, homogeneous silicon material, completely eliminating the risk of thermal stress deformation and lattice damage. Differentiated post-treatment solutions are designed for the trace SiO thin layers resulting from the process, adaptable to various reuse scenarios such as repeated carbon film deposition and other high-precision processes. It balances low cost, high cleanliness, and high versatility, with no hazardous waste discharge and no occupation of core production line capacity, making it highly adaptable to large-scale mass production. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in detail below with reference to specific experimental data.

[0022] First Embodiment

[0023] The method for regenerating carbon film dummy wafers by low-pressure oxygen-passing thermal oxidation provided by the present invention includes the following steps.

[0024] In the sorting and pretreatment step, carbon film dummy wafers with a carbon film thickness of no more than 5μm, no chipping, no cracks, and no heavy metal contamination are selected. Large foreign objects, floating dust, and loose impurities on the wafer surface are removed manually or mechanically to ensure that the wafer substrate is intact and free of large contaminants, thus avoiding affecting the subsequent thermal oxidation film removal effect.

[0025] In the low-pressure thermal oxidation decarbonization step, the pretreated wafer is placed flat and fed into a clean semiconductor low-pressure diffusion furnace tube. The furnace body is sealed, and the chamber is pressurized to 1 Torr and stabilized at this pressure. The temperature inside the furnace tube is then raised to a stable 500℃. 1000 sccm of high-purity oxygen is continuously introduced, and the oxidation is maintained at this constant temperature for 30 minutes. In this low-pressure, oxygen-rich environment, oxygen molecules can fully diffuse and penetrate into the surface of the carbon film and deep into the trenches, undergoing a complete gas-phase oxidation reaction with the amorphous carbon film. This completely converts the solid carbon film into carbon dioxide gas, which then detaches from the wafer surface, achieving complete removal of carbon films of 5μm and below, leaving no surface residue or trench dead zones.

[0026] During the furnace cooling process, heating and oxygen supply are stopped, and the wafer cools naturally to room temperature within the sealed furnace. After the carbon film is completely oxidized and removed, the wafer has a pure silicon homogeneous structure with no difference in thermal shrinkage coefficients between dissimilar materials. This fundamentally avoids problems such as thermal stress deformation, lattice damage, and wafer warping, resulting in excellent substrate structural stability and electrical performance consistency.

[0027] In the ultrapure water rinsing and isothermal drying steps, the cooled wafer is removed and thoroughly rinsed with semiconductor industry-standard ultrapure water, covering the front, back, and trench structures of the wafer. This effectively removes trace amounts of oxide dust, free particles, and residual impurities from the wafer surface, strictly controlling secondary particle contamination. Subsequently, a semiconductor standard isothermal drying process is used to complete the drying and dehydration. The entire process is a mature and clean process in the industry, requiring no special modification treatment, ultimately completing the non-destructive regeneration of the wafer.

[0028] During the process, the high-temperature, oxygen-rich environment causes a very thin SiO oxide layer to form on the silicon substrate surface. Different post-processing logic is designed to address this process characteristic and adapt to different wafer reuse scenarios. If the regenerated wafer is only used for re-depositing carbon films for recycling, the extremely thin SiO layer has no negative impact on the carbon film deposition process, film adhesion, or film quality, and can be ignored without post-processing. If the regenerated wafer is used in other high-precision semiconductor processes, after the high-temperature oxidation process, NF3 gas can be continuously introduced for 10 minutes to precisely and thoroughly remove the newly formed SiO layer on the surface, completely restoring the high-purity silicon substrate.

[0029] This invention screened and verified the process parameters through multiple sets of gradient control experiments.

[0030] Under a fixed pressure of 1 Torr, gradient experiments were conducted at temperatures of 300℃, 400℃, 500℃, 600℃, and 700℃, and the experimental data are shown in the table below. The experimental data shows a positive correlation between process temperature and carbon film recovery quality; the higher the temperature, the faster the carbon film etching rate, the better the on-wafer etching uniformity, and the lower the wafer surface roughness. Specifically, at 500℃, the etching rate was 290 nm / min, the etching rate uniformity was 1.40%, the number of surface particles was 2, and the surface roughness was 0.8 nm, fully meeting the high-quality regeneration standards for mass production. Compared to the 600℃ and 700℃ high-temperature conditions, the 500℃ condition, while fully meeting performance standards, can significantly reduce furnace heating energy consumption, reduce high-temperature aging wear of equipment, and lower mass production operation and maintenance costs.

[0031] The experimental data for different temperature gradients under a constant pressure of 1 Torr are shown in the table below:

[0032] pressure temperature Etching rate Etching rate uniformity Number of particles Roughness Ra 1Torr 300℃ 108nm / min 3.80% 121 5.6nm 1Torr 400℃ 189nm / min 3.20% 50 3.1nm 1Torr 500℃ 290nm / min 1.40% 2 0.8nm 1Torr 600℃ 356nm / min 1.20% 2 0.7nm 1Torr 700℃ 412nm / min 0.91% 4 0.5nm

[0033] Under a fixed temperature of 500℃, gradient experiments were conducted with chamber pressures of 0.2 Torr, 0.6 Torr, 1 Torr, 1.5 Torr, and 2 Torr, respectively. The experimental data are shown in the table below. The experimental data show that at 1 Torr, the etching rate is 308 nm / min, the etching rate uniformity is 1.20%, the number of surface particles is 0, and the surface roughness is 0.7 nm. This combination achieves a high etching rate, excellent intra-wafer uniformity, near-zero surface particles, and extremely low surface roughness, making it the optimal pressure parameter for the regeneration process of this invention.

[0034] The test data for different pressure gradients under a fixed temperature of 500℃ are shown in the table below:

[0035] pressure temperature Etching rate Etching rate uniformity Number of particles Roughness Ra 0.2 Torr 500℃ 58nm / min 0.60% 0 3.2nm 0.6 Torr 500℃ 128nm / min 1.10% 0 2.1nm 1Torr 500℃ 308nm / min 1.20% 0 0.7nm 1.5 Torr 500℃ 421nm / min 1.50% 5 0.7nm 2Torr 500℃ 514nm / min 2.05% 22 0.6nm

[0036] Under process conditions of 1 Torr, 500℃, and 30 min oxidation, the removal of carbon films and photoresists of different thicknesses was verified, and the experimental data are shown in the table below. The results show that carbon films with thicknesses of 50 nm, 500 nm, and 5 μm were all removed without residue, with surface particle counts of 2, 1, and 3, respectively. Removal verification of an 8 μm thick carbon film showed a small amount of residue with 58 surface particles. These experimental results clarify the mass production applicability boundary of this invention, namely, that when the carbon film thickness is no greater than 5 μm, stable residue-free and high-cleanliness removal can be achieved, fully meeting the requirements for semiconductor mass production regeneration. Simultaneously, it verifies that this process has the ability to remove relatively thin photoresists, but thick photoresists exhibit residue issues, further confirming the technical positioning of this process specifically adapted for carbon film wafer regeneration.

[0037] The following table shows the verification data of the removal effect of different film thicknesses under the conditions of 1 Torr, 500℃, and oxidation for 30 min:

[0038] Membrane materials thickness pressure temperature Etching time Etching conditions particle Carbon 50nm 1Torr 500℃ 30 minutes No residue 2 Carbon 500nm 1Torr 500℃ 30 minutes No residue 1 Carbon 5000nm (5μm) 1Torr 500℃ 30 minutes No residue 3 Carbon 8000nm (8μm) 1Torr 500℃ 30 minutes A few residues 58 Photoresist 50nm 1Torr 500℃ 30 minutes No residue 1 Photoresist 200nm 1Torr 500℃ 30 minutes No residue 1 Photoresist 400nm 1Torr 500℃ 30 minutes No residue 2 Photoresist 600nm 1Torr 500℃ 30 minutes A few residues 36 Photoresist 1000nm 1Torr 500℃ 30 minutes Residue 254

[0039] The process of this invention has significant advantages over existing technologies, as shown in the table below. Compared with wet strong oxidation cleaning process (carbon film removal rate of 80% to 88%, roughness after regeneration ≥ 2.5 nm, chemical corrosion and lattice damage, only 2 to 3 cycles, and serious trench residue) and plasma dry etching process (carbon film removal rate of 92% to 96%, roughness after regeneration 1.2 to 1.8 nm, ion bombardment micro-roughening, only 4 to 6 cycles, and residual carbon easily left at the bottom of thick films), this invention can achieve 100% carbon film removal rate under 1 Torr, 500℃ thermal oxidation conditions. This removal rate is for carbon films with a thickness of no more than 5 μm, with a roughness ≤ 0.8 nm after regeneration, no bombardment, no corrosion, zero silicon loss, ≥ 12 cycles, and no trench residue.

[0040] The performance comparison between the process scheme of this invention and the traditional process is shown in the table below:

[0041] Process scheme Carbon film removal rate Regeneration Ra Silicon substrate damage Number of cycles trench residue Wet strong oxidizing cleaning 80%~88% ≥2.5nm Chemical corrosion, lattice damage 2-3 times Serious residue Plasma dry etching 92%~96% 1.2~1.8nm Ion bombardment microroughening 4 to 6 times Thick films are prone to leaving residual carbon at the bottom. This invention involves thermal oxidation at 1 Torr / 500℃. 100% (≤5μm carbon film) ≤0.8nm No bombardment, no corrosion, zero silicon loss ≥12 times trench

[0042] Second Embodiment

[0043] The difference between this embodiment and the first embodiment lies in the type of furnace tube equipment and the corresponding adjustment of process parameters.

[0044] In this embodiment, a vertical low-pressure diffusion furnace tube is used instead of the horizontal low-pressure diffusion furnace tube in the first embodiment. Vertical and horizontal furnace tubes differ in wafer loading method and airflow distribution; in a vertical furnace tube, wafers are stacked vertically, and airflow flows vertically along the axial direction. To ensure uniform airflow distribution between wafers and batch-to-batch process consistency, the process parameters are optimized and adjusted as follows.

[0045] The sorting and pretreatment steps are the same as in the first embodiment. Carbon film dummy wafers with a carbon film thickness of no more than 5μm, no chipping, no cracks, and no heavy metal contamination are selected, and large foreign objects, floating dust, and loose impurities on the surface are removed.

[0046] In the low-pressure thermal oxidation decarbonization step, the pretreated wafers are vertically loaded into a crystal boat and fed into a vertical low-pressure diffusion furnace tube. The furnace body is sealed, and the chamber pressure is stably controlled at 1 Torr. The temperature is increased until the internal temperature of the furnace tube stabilizes at 500℃. 1000 sccm of high-purity oxygen is continuously introduced, and the oxidation is maintained at this temperature for 35 minutes. Because the airflow in the vertical furnace tube flows vertically, the uniform diffusion of oxygen molecules between the vertically stacked wafers requires a slightly longer oxidation time to ensure that the carbon film on the surface of each wafer and deep in the trenches is fully oxidized. In the low-pressure oxygen-rich environment of the vertical furnace tube, oxygen molecules can also fully diffuse and penetrate into the surface of the carbon film and deep in the trenches, undergoing a sufficient gas-phase oxidation reaction with the amorphous carbon film. This completely converts the solid carbon film into carbon dioxide gas, which detaches from the wafer surface, achieving complete removal of carbon films of 5μm and below.

[0047] The furnace cooling process is the same as in the first embodiment, with heating and oxygen supply stopped, and the wafer naturally cooled to room temperature within the sealed furnace. After the carbon film is completely oxidized and removed, the wafer has a pure silicon homogeneous structure, without the difference in thermal shrinkage coefficients between dissimilar materials, thus fundamentally avoiding defects such as thermal stress deformation, lattice damage, and wafer warping.

[0048] The ultrapure water cleaning and constant temperature drying steps are the same as in the first embodiment. After the wafer has been cooled, the front, back and trench structures of the wafer are rinsed with semiconductor industry standard ultrapure water. Then, the wafer is dried and dehydrated using semiconductor standard constant temperature drying process.

[0049] In this embodiment, carbon film removal with thicknesses of 50 nm, 500 nm, and 5 μm was verified under process conditions of 1 Torr, 500 °C, and 35 min oxidation, and all achieved residue-free removal. The vertical furnace tube can process more wafers per batch than the horizontal furnace tube, further improving mass production efficiency while ensuring the same regenerated quality. A trace amount of SiO thin layer is also generated on the silicon substrate surface during the process, which can be adapted using the same differentiated post-processing logic as in the first embodiment.

[0050] This embodiment achieves higher single-batch capacity and further improves mass production economy by replacing the horizontal furnace tube with a vertical furnace tube and adjusting the oxidation holding time to 35 minutes, while ensuring the same regeneration quality of 100% residue-free removal of carbon films of 5μm and below, low particle size, low roughness, and zero silicon substrate damage.

Claims

1. A method for regenerating carbon film dummy wafers through low-pressure oxygen-assisted thermal oxidation, characterized in that, Includes the following steps: (1) Sorting pretreatment: Select carbon film dummy wafers with a carbon film thickness of no more than 5μm, no chipping, no cracks, and no heavy metal contamination, and remove large foreign objects, floating dust and loose impurities from the surface; (2) Place the pretreated wafer into a low-pressure furnace tube, seal the furnace body and stabilize the chamber pressure at 1 Torr, raise the temperature and maintain it at 500°C, continuously introduce 1000 sccm of high-purity oxygen, and perform constant temperature oxidation treatment for 30 min to completely oxidize the carbon film on the wafer surface and in the trenches into carbon dioxide gas that is removed from the wafer substrate. (3) Stop heating and oxygen supply, and allow the wafer to cool naturally to room temperature in the sealed furnace. (4) Take out the cooled wafer, rinse the front, back and trench structures of the wafer with semiconductor standard ultrapure water, and then dry and remove water using semiconductor standard constant temperature drying process.

2. The method for regenerating carbon film dummy wafers by low-pressure oxygen-flushing thermal oxidation according to claim 1, characterized in that: Under standard operating conditions of 1 Torr and 500℃, the carbon film etching rate stably reaches 290~308nm / min, the on-wafer etching uniformity is ≤1.40%, the surface roughness Ra of the regenerated wafer is ≤0.8nm, and the number of surface particles is ≤3.

3. The method for regenerating carbon film dummy wafers by low-pressure oxygen-flushing thermal oxidation according to claim 1, characterized in that: Gradient temperature tests have verified that process temperature is positively correlated with carbon film etching rate, surface cleanliness, and surface roughness. The recycling performance is better at high temperatures of 600℃ and 700℃. However, this invention prefers the low temperature condition of 500℃ to maximize the benefits of mass production with lower energy consumption and lower equipment wear.

4. The method for regenerating carbon film dummy wafers by low-pressure oxygen-flushing thermal oxidation according to claim 1, characterized in that: When the carbon film thickness exceeds 5μm, the film layer is not completely removed. Therefore, the thickness of the incoming carbon film is strictly limited to no more than 5μm.

5. The method for regenerating carbon film dummy wafers by low-pressure oxygen-flushing thermal oxidation according to claim 1, characterized in that: The oxidation process involves only gas-phase oxidation, without ion bombardment or chemical corrosion. The silicon substrate experiences no thickness loss or lattice micro-damage, and the wafer can be recycled at least 12 times.

6. The method for regenerating carbon film dummy wafers by low-pressure oxygen-flushing thermal oxidation according to claim 1, characterized in that: This method is applicable to the regeneration of dummy wafers with planar carbon films and carbon films embedded in large-aperture trenches, with no carbon residue inside the trenches.

7. The method for regenerating carbon film dummy wafers by low-pressure oxygen-flushing thermal oxidation according to claim 1, characterized in that: After the carbon film is completely removed, the wafer has a pure silicon homogeneous structure, which in principle completely eliminates the risk of thermal stress deformation and lattice damage.

8. The method for regenerating carbon film dummy wafers by low-pressure oxygen-flushing thermal oxidation according to claim 1, characterized in that: During the process, a small amount of SiO thin layer is generated on the surface of the silicon substrate, which can achieve differentiated adaptation treatment. When the wafer is repeatedly deposited with carbon film, the SiO thin layer is directly retained without affecting the subsequent carbon film preparation and performance. When applied to other high-precision processes, after the high-temperature oxidation process is completed, NF3 gas is introduced for constant temperature treatment for 10 minutes to completely remove the SiO layer and restore the high-purity silicon substrate.

9. The method for regenerating carbon film dummy wafers by low-pressure oxygen-flushing thermal oxidation according to claim 1, characterized in that: Under constant temperature of 500℃, gradient tests were conducted with chamber pressures set to 0.2 Torr, 0.6 Torr, 1 Torr, 1.5 Torr, and 2 Torr, respectively. Under the 1 Torr condition, the etching rate was 308 nm / min, the on-chip etching uniformity was 1.20%, the number of surface particles was 0, and the surface roughness was 0.7 nm. These were the optimal pressure parameters that balanced etching rate, on-chip uniformity, surface particles, and surface roughness.

10. The method for regenerating carbon film dummy wafers by low-pressure oxygen-flushing thermal oxidation according to claim 1, characterized in that: Under the process conditions of 1 Torr, 500℃, and oxidation for 30 min, the removal of carbon films with thicknesses of 50 nm, 500 nm, and 5 μm was verified, and all were removed without residue, with the number of surface particles being 2, 1, and 3, respectively. The removal of carbon films with a thickness of 8 μm was verified, and a small amount of residue appeared with the number of surface particles being 58. When the thickness of the carbon film is exceeded, the complete removal effect and wafer cleanliness cannot be guaranteed.