CN114975114A - Wafer recycling method - Google Patents
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- CN114975114A CN114975114A CN202110214746.2A CN202110214746A CN114975114A CN 114975114 A CN114975114 A CN 114975114A CN 202110214746 A CN202110214746 A CN 202110214746A CN 114975114 A CN114975114 A CN 114975114A
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- 238000000034 method Methods 0.000 title claims abstract description 63
- 238000004064 recycling Methods 0.000 title description 17
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 75
- 238000000137 annealing Methods 0.000 claims abstract description 72
- 238000005498 polishing Methods 0.000 claims abstract description 25
- 238000004140 cleaning Methods 0.000 claims abstract description 21
- 238000002360 preparation method Methods 0.000 claims abstract description 6
- 238000010438 heat treatment Methods 0.000 claims description 10
- 230000001172 regenerating effect Effects 0.000 claims 1
- 229910052802 copper Inorganic materials 0.000 abstract description 12
- 239000010949 copper Substances 0.000 abstract description 12
- 238000011069 regeneration method Methods 0.000 abstract description 7
- 230000008901 benefit Effects 0.000 abstract description 5
- 230000008929 regeneration Effects 0.000 abstract description 4
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- 239000004065 semiconductor Substances 0.000 description 4
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/324—Thermal treatment for modifying the properties of semiconductor bodies, e.g. annealing, sintering
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/82—Recycling of waste of electrical or electronic equipment [WEEE]
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
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- Mechanical Treatment Of Semiconductor (AREA)
Abstract
The invention provides a wafer regeneration method. It includes: the method comprises the steps of preparation, membrane removal, annealing, polishing and cleaning. The invention reduces the copper atom concentration on the surface of the regeneration wafer by regulating and controlling the temperature of the annealing step. The invention can reduce the risk of copper pollution and has the advantage of good cost benefit.
Description
Technical Field
The present invention relates to a wafer recycling method, and more particularly, to a wafer recycling method for reducing copper contamination.
Background
Because the wafer has extremely high requirements on process stability and dust particle number, in the process of manufacturing semiconductor integrated circuits, a wafer factory needs to Monitor the process by using a Monitor wafer for the process performance and the dust-free environment, and in addition, before the machine platform goes on-line again for the process, a Dummy wafer needs to be used for adjusting the parameters of a heat engine and the machine platform, based on the cost consideration, the Dummy wafer and the Monitor wafer can both perform the wafer regeneration process, and the more times of recovery testing, the more beneficial the reduction of the manufacturing cost, so the wafer regeneration technology is more and more emphasized.
In addition, in response to the demand for miniaturization of electronic products, the technology of semiconductor chips is also required to be improved to ensure that the reliability of the circuit can be maintained after the circuit is miniaturized, and the process technology is a classic example of upgrading the conductive wire material by replacing aluminum with copper. However, even though copper has better conductivity and electromigration (electromigration) resistance than aluminum, which can improve the problems of leakage current and circuit heating caused by circuit scaling, copper itself has high activity, so that it is an important technical threshold to prevent copper from contaminating semiconductor process equipment. Furthermore, when the wafer is to be recycled, how to reduce the risk of copper contamination of the wafer is important. Therefore, there is a need to develop a wafer recycling process that effectively reduces the copper contamination level.
Disclosure of Invention
In view of the technical drawbacks of the prior art, it is an object of the present invention to provide a wafer recycling method capable of reducing the copper atom content on the surface of the recycled wafer in a simple and effective manner.
To achieve the above object, the present invention provides a wafer recycling method, comprising: the preparation method comprises the following steps: preparing a wafer with at least one film layer on the surface, wherein the wafer contains copper atoms; a step of removing the film: stripping the film layer from the surface of the wafer to obtain a stripped wafer; and (3) annealing: placing the film-removed wafer in a heating environment for annealing treatment to obtain an annealed wafer, wherein the annealing temperature is more than or equal to 150 ℃ and less than or equal to 500 ℃; and (3) polishing: polishing the annealed wafer to obtain a polished wafer; and a cleaning step: cleaning the polished wafer to obtain a regenerated wafer.
According to the invention, the wafer is a used wafer, and is converted into a recycled wafer after the wafer recycling method of the invention.
In some embodiments, the recycled wafer may be a control wafer or a barrier wafer.
The invention can accelerate the diffusion rate of copper atoms contained in the film-removed wafer from a high unit content area to a low unit content area by carrying out the annealing step in a specific annealing temperature range so as to ensure that the copper atoms contained in each plane area in the film-removed wafer are distributed more evenly and can be separated out to the surface of the film-removed wafer more quickly, and then the polishing step is matched to remove the copper atoms so as to reduce the concentration of the copper atoms in the used wafer.
In one embodiment, the annealing step is furnace heating or oven heating.
Preferably, the annealing step includes heating in a protective atmosphere to prevent oxidation of the wafer by oxygen in the air. In one embodiment, the protective atmosphere is nitrogen, but is not limited thereto.
Preferably, after the annealing step is completed, the annealed wafer is moved out of the heating apparatus (e.g., furnace tube or oven), and then is allowed to stand to cool the annealed wafer to room temperature, so as to prevent the quality of the annealed wafer from being affected by too much temperature variation.
In one embodiment, the duration of the annealing step is at least 1 hour; preferably, the duration of the annealing treatment is at least 2 hours. In addition, the duration of the annealing step of the present invention does not include ramp-up and ramp-down times.
In one embodiment, the duration of the annealing step is from 1 hour to 9 hours; preferably, the duration of the annealing step is 2 to 6 hours; more preferably, the duration of the annealing treatment is 3 hours. The duration of the annealing step is beneficial to uniformly dispersing the copper atoms in the reclaimed wafer and transferring the copper atoms to the surface of the wafer, and the concentration of the copper atoms on the surface of the reclaimed wafer and the precipitation rate of the copper atoms can be reduced after the polishing step and the cleaning step.
In one embodiment, the annealing temperature is any one of 150 ℃ to 500 ℃, for example: 150 deg.C, 160 deg.C, 170 deg.C, 180 deg.C, 190 deg.C, 200 deg.C, 210 deg.C, 220 deg.C, 230 deg.C, 240 deg.C, 250 deg.C, 260 deg.C, 270 deg.C, 280 deg.C, 290 deg.C, 300 deg.C, 350 deg.C, 400 deg.C, 450 deg.C or 500 deg.C; preferably, the annealing temperature is 250 ℃.
The invention controls the range of annealing temperature, and has the following advantages: (1) accelerating the copper atoms to move (migration) in the film-removed wafer and separate out on the surface of the annealed wafer; (2) to avoid the annealing temperature being too low to effectively precipitate copper atoms on the surface of the annealed wafer, or to extend the duration of the annealing step without incurring time costs.
According to the present invention, the stripping step is performed in a manner comprising: chemical stripping such as wet etching, or physical bombardment such as plasma treatment, but not limited thereto. The stripped wafer obtained after the step can have a rough surface.
In one embodiment, the wafer reclamation method further comprises a cleaning step after the stripping step: cleaning the stripped wafer to obtain a cleaned stripped wafer. In this embodiment, the annealing step is performed by annealing the cleaned and stripped wafer in a heated environment. The invention can remove the metal remained on the surface of the wafer after the film is removed by a cleaning step, such as: copper and aluminum.
Preferably, a standing step is further performed between the annealing step and the polishing step to precipitate copper atoms inside the wafer onto the surface of the wafer.
Preferably, the standing time of the standing step is 0.5 to 9 days; more preferably, the standing time of the standing step is 3 days to 7 days.
Preferably, the environment of the standing step is a clean room.
In one embodiment, the cleanroom is in compliance with the Federal Standard 209(FED 209) Class1000 of the united states Federal Standard 209, i.e., the number of air particles having a particle size greater than or equal to 0.5 microns per cubic foot of air is less than or equal to 1000; or the clean room conforms to ISO 14644 ISO 6, that is, the number of air particles with the particle size of more than or equal to 0.5 micrometer contained in each cubic meter of air is less than or equal to 35,200.
Preferably, the polishing step is performed in a manner comprising: rough polishing and/or fine polishing, but is not limited thereto. The invention removes the copper atoms precipitated on the surface of the annealed wafer through the polishing step, and can further slow down the precipitation rate of the subsequent copper atoms because the surface of the polished wafer can have lower surface roughness and higher surface free energy.
In one embodiment, the polishing step performs rough polishing and finish polishing on both the front and back surfaces of the annealed wafer, respectively.
In one embodiment, the cleaning step comprises: RCA silicon chip cleaning method. The RCA silicon wafer cleaning method uses a chemical solution containing ammonium hydroxide (NH) 4 OH) and hydrogen peroxide (H) 2 O 2 ) The mixed solution of (a), a mixed solution of hydrochloric acid (HCl) and hydrogen peroxide, a mixed solution of hydrofluoric acid (HF) and hydrogen peroxide, or a mixed solution of ozone Water (oxygenated DI Water) and hydrogen peroxide, but is not limited thereto. The cleaning step removes metal impurities and particles.
In one embodiment, the wafer recycling method sequentially performs the preparation step, the film removal step, the annealing step, the polishing step, and the cleaning step to obtain the recycled wafer.
In one embodiment, the wafer recycling method sequentially performs the preparation step, the film removal step, the cleaning step, the annealing step, the standing step, the polishing step, and the cleaning step to obtain the recycled wafer.
In one embodiment, the surface of the stripped wafer has a copper atom concentration of at least 10 12 Per cm 2 The surface of the recycled wafer obtained by the wafer recycling method of the present invention has a copper atom concentration of 1 × 10 8 Per cm 2 To 5X 10 9 Per cm 2 . Therefore, the concentration of copper atoms contained in the film-removed wafer is at least 200 times higher than that of the regenerated wafer, so the regenerated wafer can avoid serious copper pollution.
In one embodiment, the surface of the reclaimed wafer obtained by the wafer reclaiming method of the present invention has a copper atom concentration of 1 × 10 9 Per cm 2 To 5X 10 9 Per cm 2 。
In the present specification, the copper atom concentration refers to the number of copper atoms per unit area contained in the surface of the regenerated wafer. The copper atom concentration of the surface of the reclaimed wafer is a result of measuring a solution obtained by acid etching the surface of the reclaimed wafer. Preferably, the target for sampling is 12 "reconstituted wafers.
In one embodiment, the copper atom concentration of the invention is obtained by detecting a sample acid etching solution by an inductively coupled plasma mass spectrometer (ICP-MS), and the acid etching thickness reaches 5 nanometers below the surface of the regeneration wafer.
The invention can reduce the copper atom concentration on the surface of the regenerated wafer to be less than or equal to 5 multiplied by 10 by controlling the annealing temperature, the duration of the annealing treatment and the standing time 9 Per cm 2 (ii) a Preferably, the copper atom concentration on the surface of the recycled wafer can be reduced to 1 × 10 8 Per cm 2 So as to prevent the regenerated wafer from continuously precipitating a large amount of copper atoms in the subsequent standby storage process, which causes the copper atoms to pollute the high-precision semiconductor process machine.
In conclusion, the wafer regeneration method can reduce the precipitation amount of copper atoms on the surface of the regenerated wafer, reduce the risk of copper pollution in the subsequent process and improve the quality of the regenerated wafer; and greatly reduces the process energy consumption, and has better cost benefit.
Drawings
Fig. 1 is a flowchart of a wafer reclamation method according to embodiments 1 to 5.
Fig. 2 is a flowchart of a wafer reclamation method of embodiments 6 and 7.
Detailed Description
Hereinafter, those skilled in the art can easily understand the advantages and effects of the present invention from the following examples. Therefore, it is to be understood that the description set forth herein is intended merely to illustrate preferred embodiments and not to limit the scope of the invention, which can be modified and varied to practice or apply the teachings of the present invention without departing from the spirit and scope thereof.
As shown in fig. 1, the wafer recycling method of the present invention includes step S1: the preparation method comprises the following steps: preparing a wafer with at least one film layer on the surface, wherein the wafer contains copper atoms; step S2: a step of removing the film: stripping the film layer from the surface of the wafer to obtain a stripped wafer; step S3: and (3) annealing: placing the film-removed wafer in a heating environment for annealing treatment to obtain an annealed wafer, wherein the annealing temperature is more than or equal to 150 ℃ and less than or equal to 500 ℃; step S4: and (3) polishing: polishing the annealed wafer to obtain a polished wafer; and step S5: a cleaning step: cleaning the polished wafer to obtain a regenerated wafer. Hereinafter, examples 1 to 5 are a wafer recycling method using the flow steps shown in fig. 1.
As shown in fig. 2, the wafer recycling method of the present invention includes step S1: and (5) preparing. Step S2: the film removing step, specifically, the step S2, may be a wet etching or a plasma treatment. Step S3: the annealing step, specifically, the step S3 may adopt furnace tube heating or oven heating. Step S3-1: the resting step, specifically, step S3-1, may be to rest the annealed wafer in the clean room of Class1000 of Federal Standard 209 for 3 to 7 days. Step S4: the polishing step, specifically, step S4, may polish the front and back surfaces of the annealed wafer with a silica abrasive, respectively. Step S5: cleaning step, specifically, step S5 may employ a standard RCA silicon wafer cleaning method. Hereinafter, examples 6 and 7 are methods of recycling wafers using the flow steps shown in fig. 2.
Reference example 1: recycled wafer
A12-inch wafer with an oxide film layer on the surface is prepared, and the wafer contains copper atoms. Then, a stripping step is performed by a chemical stripping method to strip the oxide film layer from the surface of the wafer, so as to obtain a stripped wafer, which is the recycled wafer of reference example 1.
Example 1: recycled wafer
A12-inch wafer with an oxide film layer on the surface is prepared, and the wafer contains copper atoms. Then, a chemical stripping process is used to strip the oxide film layer from the surface of the wafer, so as to obtain a stripped wafer. Then, the film-removed wafer was placed in an atmosphere of 150 ℃ filled with nitrogen gas and subjected to annealing treatment for 3 hours continuously. After the annealing step is finished, carrying out rough polishing on the annealed wafer by using a silicon dioxide abrasive to obtain a polished wafer; and cleaning the polished wafer by using a mixed solution of hydrofluoric acid and hydrogen peroxide to finally obtain a regenerated wafer.
Example 2 to example 5: recycled wafer
Example 2 the procedure of example 1 was followed, except that the annealing temperature was 200 ℃.
Example 3 the procedure of example 1 was followed except that the annealing temperature was 250 ℃.
Example 4 the procedure of example 1 was followed except that the annealing temperature was 250 c and the duration of the annealing treatment was 1 hour.
Example 5 the procedure of example 1 was followed except that the annealing temperature was 250 c and the duration of the annealing treatment was 9 hours.
Example 6 the same procedure as in example 3 was repeated, except that a standing step was added between the annealing step and the polishing step; wherein the environment of the standing step is a Class1000 clean room which meets the American Federal standard 209, and the standing time is 3 days.
Example 7 the procedure of example 6 was followed, except that the standing time was 7 days.
Comparative example 1 to comparative example 3: recycled wafer
Comparative example 1 the procedure of example 1 was followed except that the annealing step was not performed.
Comparative example 2 the same procedure as in example 6 was repeated except that the annealing step was not performed.
Comparative example 3 the procedure of example 7 was followed except that the annealing step was not performed.
Analysis 1: process variation and copper atom concentration
Whether the 12-inch recycled wafers of reference example 1, examples 1 to 5 and comparative example 1 used in the analysis were subjected to the annealing step, and the respective annealing temperatures and the duration of the annealing treatment were set as shown in table 1, and the oxide layer on the surface of each group of samples was dissolved by an automatic rolling machine using a hydrofluoric acid diluent, and the sampling range was an interval from the surface to 5 nm deep below the surface of each group of samples, to obtain each group of samples to be measured; then, each group of samples to be tested was analyzed by high resolution inductively coupled plasma mass spectrometer for copper atom concentration in the solution, and the analysis results of each group are shown in table 1.
Table 1: whether or not the reclaimed wafers of reference example 1, examples 1 to 5 and comparative example 1 were subjected to the annealing step, the annealing temperature in the annealing step, the duration of the annealing treatment and the copper atom concentration
As can be seen from Table 1, reference example 1 had a surface copper atom concentration of 1X 10 before the annealing step 12 Per cm 2 In examples 1 to 5, the concentration of copper atoms on the surface of the recycled wafer is greatly reduced after the wafer recycling method of the present invention, for example, example 1 is reduced by 0.005 times compared with reference example 1, and even example 5 is reduced by 0.001 times compared with reference example 1.
The surface copper atom concentration of the reconstituted wafer of comparative example 1 was 2 × 10 as compared with examples 1 to 5 11 Per cm 2 Also 40 times to 200 times as compared with examples 1 to 5. It can be confirmed that the wafer reclamation method of the present invention can surely reduce the copper atom concentration on the surface of the reclaimed wafer obtained by performing the annealing step.
Furthermore, from the results of comparing the surface copper atom concentrations of the reclaimed wafers of examples 1 to 3, it is understood that increasing the annealing temperature contributes to a decrease in the copper atom concentration on the surface of the reclaimed wafer.
Further, from the results of comparing the surface copper atom concentrations of the reclaimed wafers of examples 3 to 5, it is understood that increasing the duration of the annealing treatment contributes to a decrease in the copper atom concentration of the reclaimed wafer surface.
Finally, although the concentration of copper atoms on the surface of example 5 is lower than that of example 3, the difference is not great, so if the annealing temperature is 250 ℃ and the duration of the annealing treatment is 3 hours, the required energy can be reduced, and the cost efficiency is better.
Analysis 2: difference in standing step and copper atom concentration
The differences in the standing times of examples 3, 6 and 7 and comparative examples 1 to 3 used in the analysis are shown in Table 2, and the samples of each group were sampled and prepared in the same manner as the samples of example 1; then, each sample to be tested was analyzed by high resolution inductively coupled plasma mass spectrometer for copper atom concentration in the dissolution solution, and the results are shown in table 2.
Table 2: standing time and copper atom concentration of examples 3, 6 and 7 and comparative examples 1 to 3
| Group of | Standing time | Copper atom concentration (piece/cm) 2 ) |
| Example 3 | Day 0 | 1.5×10 9 |
| Example 6 | 3 days | 1.3×10 9 |
| Example 7 | 7 days | 1×10 9 |
| Comparative example 1 | Day 0 | 2×10 11 |
| Comparative example 2 | 3 days | 3.2×10 11 |
| Comparative example 3 | 7 days | 4×10 11 |
As is clear from the results of comparing the surface copper atom concentrations of the reclaimed wafers of example 3, example 6, and example 7 in table 2, the copper atom concentration of the reclaimed wafer surface can be further reduced by adding the standing step between the annealing step and the polishing step; meanwhile, the longer the standing step is, the better the effect is.
From the comparison of the surface copper atom concentrations of the reconstituted wafers of comparative examples 1 to 3 in table 2, it is understood that the standing step does not contribute to the reduction of the copper atom concentration on the surface of the reconstituted wafer, and rather increases the copper atom concentration on the surface of the reconstituted wafer, if the annealing step is not performed, and it is understood that the annealing step of the present invention can surely accelerate the deposition of copper atoms inside the reconstituted wafer.
As can be seen from the comparison of the surface copper atom concentrations of the reclaimed wafers of example 6 and comparative example 2 in table 2, the surface copper atom concentration of the reclaimed wafer obtained by carrying out the annealing step after the wafer reclaiming method of the present invention in example 6 is greatly reduced to 0.004 times.
As can be seen from the comparison of the surface copper atom concentrations of the recycled wafers of example 7 and comparative example 3 in table 2, the annealing step was carried out after the wafer recycling method of the present invention in example 6, and the surface copper atom concentration of the recycled wafer was greatly reduced to 0.0025 times.
In summary, the wafer reclamation method of the present invention can actually effectively reduce the copper atom concentration on the surface of the reclaimed wafer through the combination of the annealing step and the subsequent polishing step. In addition, when the wafer regeneration method further comprises a standing step, the concentration of copper atoms on the surface of the regenerated wafer can be further reduced, and copper pollution in the subsequent process caused by the precipitation of the copper atoms on the surface of the regenerated wafer during the subsequent standby storage period of the regenerated wafer is avoided.
Claims (9)
1. A method of regenerating a wafer, comprising:
the preparation method comprises the following steps: preparing a wafer with at least one film layer on the surface, wherein the wafer contains copper atoms;
and (3) film removal: stripping the film layer from the surface of the wafer to obtain a stripped wafer;
and (3) annealing: placing the film-removed wafer in a heating environment for annealing treatment to obtain an annealed wafer, wherein the annealing temperature is more than or equal to 150 ℃ and less than or equal to 500 ℃;
and (3) polishing: polishing the annealed wafer to obtain a polished wafer; and
a cleaning step: cleaning the polished wafer to obtain a regenerated wafer.
2. The method of claim 1, wherein the annealing step is performed for an annealing duration of at least 1 hour.
3. The method as claimed in claim 2, wherein the annealing step is performed for a duration of 2 to 6 hours.
4. The wafer reclamation method of claim 1, wherein the annealing temperature is 250 ℃.
5. The wafer reclaiming method as claimed in claim 1, further comprising a standing step between the annealing step and the polishing step of the wafer reclaiming method.
6. The wafer reclaiming method as claimed in claim 5, wherein the standing time of the standing step is 3 days to 7 days.
7. The method of claim 5, wherein the environment of the step of standing is a clean room.
8. The method of claim 7, wherein the clean room complies with the Class1000 of federal standard 209 or ISO 6 of ISO 14644.
9. The wafer reclaiming method as claimed in claim 1, wherein the surface of the reclaimed wafer has a copper atom concentration of 1 x 10 8 Per cm 2 To 5X 10 9 Per cm 2 。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110214746.2A CN114975114A (en) | 2021-02-26 | 2021-02-26 | Wafer recycling method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110214746.2A CN114975114A (en) | 2021-02-26 | 2021-02-26 | Wafer recycling method |
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| CN114975114A true CN114975114A (en) | 2022-08-30 |
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- 2021-02-26 CN CN202110214746.2A patent/CN114975114A/en active Pending
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