Method for cleaning single crystal silicon crucible bottom material

Abstract

The present application relates to the technical field of silicon material purification, and particularly provides a cleaning method for single crystal silicon crucible bottom material. The method aims to solve the problems of long cleaning and recovery processing time of the silicon material recovered from the cleaning of the crucible bottom material and low purity of the recovered silicon material in the prior art. To this end, the cleaning method for the single crystal silicon crucible bottom material comprises acid soaking, mixed acid cleaning and water washing. Before the acid soaking step, the cleaning method further comprises subjecting the to-be-processed crucible bottom material to plasma pretreatment. The cleaning method of the present application can increase the surface silanol group on the quartz surface by subjecting the crucible bottom material to plasma pretreatment, so that the silanol group can promote the reaction between the quartz and hydrofluoric acid as a reaction center during the soaking of the crucible bottom material in the hydrofluoric acid solution, improve the reaction speed, and thus save time and improve the cleaning efficiency.

Description

Technical Field

[0001] This invention relates to the field of silicon material purification technology, specifically providing a method for cleaning the bottom material of a single-crystal silicon crucible. Background Technology

[0002] During the Czochralski (CZ) single crystal pulling process, excess silicon material remains in the quartz crucible, forming crucible bottom material that cannot be fully utilized. This bottom material accounts for more than 3% of the total silicon material fed into the furnace. Furthermore, it accumulates significant amounts of metallic impurities during crystal pulling, and its direct contact with the quartz crucible makes complete separation difficult. Consequently, the bottom material is unusable as silicon for single crystal pulling, resulting in substantial waste. Therefore, a method for cleaning the crucible bottom material is needed to effectively remove metallic impurities and quartz, maximizing silicon utilization.

[0003] Currently, there are two main methods used. The first method involves manually separating silicon and quartz into fragments, then soaking the fragments in hydrofluoric acid to remove the quartz. However, this method is usually time-consuming and requires a large amount of hydrofluoric acid, which is not conducive to reducing production costs. The second method utilizes the different coefficients of thermal expansion of quartz and silicon. By heating and cooling, thermal stress is generated at the contact surface between the quartz and silicon, causing cracks at the contact surface and achieving separation. Alternatively, the difference in melting points between quartz and silicon can be utilized to separate the silicon and quartz through remelting. However, both of these methods require a large amount of heat, are time-consuming, and at high temperatures, impurities are easily allowed to diffuse into the silicon, failing to meet the quality requirements of pulled monocrystalline silicon.

[0004] Accordingly, the field needs a new technical solution to address the aforementioned technical problems. Summary of the Invention

[0005] The present invention aims to solve the above-mentioned technical problems, namely, to solve the problems of long cleaning and recycling time and low purity of silicon material recovered by washing bottom material in the prior art.

[0006] The present invention provides a cleaning method for the bottom material of a monocrystalline silicon crucible. The cleaning method includes acid soaking, mixed acid cleaning and water washing in sequence. Before the acid soaking step, the cleaning method further includes plasma pretreatment of the crucible bottom material to be treated.

[0007] In the preferred embodiment of the above-mentioned cleaning method for single-crystal silicon crucible bottom material, the plasma pretreatment includes: placing the crucible bottom material to be treated in the reaction chamber of a plasma generator, and introducing a first mixed gas of water vapor and argon into the reaction chamber to perform plasma pretreatment on the crucible bottom material to be treated.

[0008] In the preferred embodiment of the above-mentioned cleaning method for single-crystal silicon crucible bottom material, a dry etching process is further included between the plasma pretreatment step and the acid immersion step.

[0009] In the preferred embodiment of the above-mentioned cleaning method for the bottom material of the single crystal silicon crucible, the dry etching process includes: evacuating the reaction chamber, introducing a second mixed gas of nitrogen and hydrogen fluoride into the reaction chamber when the internal pressure of the reaction chamber drops to a first preset pressure range, and maintaining the internal pressure of the reaction chamber within the second preset pressure range, so as to perform dry etching on the bottom material of the crucible using hydrogen fluoride gas.

[0010] In the preferred embodiment of the above-mentioned cleaning method for the bottom material of the monocrystalline silicon crucible, during the plasma pretreatment process, the volume percentage of water vapor in the first mixed gas is 0.5% to 1.5%; and / or, during the plasma pretreatment process, the flow rate of the first mixed gas is 60 sccm to 80 sccm; and / or, during the plasma pretreatment process, the plasma pretreatment time is 15 min to 30 min; and / or, during the plasma pretreatment process, the voltage of the plasma generator is 7 to 9 kV and the operating frequency is 15 kHz.

[0011] In the preferred embodiment of the above-mentioned cleaning method for the bottom material of the monocrystalline silicon crucible, during the plasma pretreatment process, the volume percentage of water vapor in the first mixed gas is 1%; and / or, during the plasma pretreatment process, the flow rate of the first mixed gas is 65 sccm to 70 sccm; and / or, during the plasma pretreatment process, the plasma pretreatment time is 20 min.

[0012] In the preferred embodiment of the above-mentioned cleaning method for the bottom material of the monocrystalline silicon crucible, during the dry etching process, the first preset pressure range is 5 Pa to 10 Pa; and / or, during the dry etching process, the second preset pressure range is 18 Pa to 22 Pa; and / or, during the dry etching process, the volume percentage of hydrogen fluoride in the second mixed gas is 5% to 10%; and / or, during the dry etching process, the dry etching time is 10 h to 15 h.

[0013] In the preferred embodiment of the above-mentioned cleaning method for the bottom material of the single crystal silicon crucible, during the dry etching process, the volume percentage of hydrogen fluoride in the second mixed gas is 8%; and / or, during the dry etching process, the dry etching time is 12 hours; and / or, during the dry etching process, the plasma equipment heats the bottom material of the crucible to 500°C to 800°C.

[0014] In the preferred embodiment of the above-mentioned cleaning method for the bottom material of a single-crystal silicon crucible, during the dry etching process, the plasma equipment heats the bottom material of the crucible to 500°C.

[0015] In the preferred embodiment of the above-mentioned cleaning method for the bottom material of monocrystalline silicon crucible, the acid soaking includes: soaking the bottom material of the crucible with hydrofluoric acid solution; and / or, a water washing step is further included between the acid soaking step and the mixed acid cleaning step.

[0016] In the preferred embodiment of the above-mentioned cleaning method for the bottom material of the monocrystalline silicon crucible, the temperature of the hydrofluoric acid solution during the acid soaking process is 55℃~65℃; and / or, the soaking time of the soaking treatment during the acid soaking process is 20h~30h.

[0017] In the preferred embodiment of the above-mentioned cleaning method for the bottom material of the monocrystalline silicon crucible, the temperature of the hydrofluoric acid solution is 60°C during the acid soaking process.

[0018] In the preferred embodiment of the above-mentioned cleaning method for the bottom material of the monocrystalline silicon crucible, the soaking time of the soaking treatment during the acid soaking process is 24 hours.

[0019] The cleaning method of this application has the following technical effects:

[0020] 1. First, use steam to perform plasma pretreatment on the crucible bottom material to increase surface silanol groups on the quartz surface. During the process of soaking the crucible bottom material in hydrofluoric acid solution, the silanol groups, as reaction centers, can promote the reaction between quartz and hydrofluoric acid, increase the reaction rate, and thus save time and improve cleaning efficiency.

[0021] 2. After plasma pretreatment, the bottom material of the crucible is dry-etched with hydrogen fluoride at high temperature, which can increase the roughness of the quartz, increase the separation rate of quartz and silicon, provide a high specific surface area when the bottom material of the crucible is soaked in hydrofluoric acid, further improve the reaction rate of hydrofluoric acid and quartz, thereby saving the time required for hydrofluoric acid soaking and improving cleaning efficiency. Attached Figure Description

[0022] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0023] Figure 1 This is a flowchart of the first embodiment of the cleaning method for the bottom material of the monocrystalline silicon crucible of this application.

[0024] Figure 2 This is a flowchart of the second embodiment of the cleaning method for the bottom material of the monocrystalline silicon crucible of this application. Detailed Implementation

[0025] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0026] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0027] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0028] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0029] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0030] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0031] Unless otherwise specified, the experimental methods in the following examples are conventional methods, and the materials and reagents used in the following examples are commercially available unless otherwise specified.

[0032] As mentioned in the background section, the silicon material recovered from the bottom of the crucible through cleaning has low purity and requires a long cleaning time.

[0033] This application provides a method for cleaning the bottom material of a single crystal silicon crucible. Before soaking in hydrofluoric acid, the bottom material is pretreated with plasma using water vapor to increase the surface silanol groups on the quartz surface. The silanol groups act as reaction centers to promote the reaction between the quartz and hydrofluoric acid, thereby increasing the reaction rate and saving the time required for hydrofluoric acid soaking, thus improving the cleaning efficiency.

[0034] Specifically, please refer to Figure 1 The cleaning method for the bottom material of the monocrystalline silicon crucible in this application specifically includes the following steps:

[0035] S1: Crush the bottom material of the crucible into granules and screen out the bottom material containing residual quartz as the bottom material to be processed.

[0036] S2: Place the crucible bottom material to be treated in the reaction chamber of the plasma generator, and introduce a first mixed gas of water vapor and argon into the reaction chamber to perform plasma pretreatment on the crucible bottom material to be treated, so as to obtain the first treated crucible bottom material.

[0037] During the plasma pretreatment of the crucible bottom material, water molecules (H2O) are decomposed into OH radicals, H atoms, and active particles in a high-energy environment. The quartz surface originally contains a small amount of natural silanol groups (Si-OH). The high-energy OH radicals react with the silicon atoms on the quartz surface, thereby generating more silanol groups (Si-OH) on the quartz surface.

[0038] S4: Transfer the processed crucible bottom material to a hydrofluoric acid solution for soaking treatment to obtain silicon material.

[0039] In step S4, the bottom material of the crucible is soaked in hydrofluoric acid solution, thereby allowing the hydrofluoric acid to react with the quartz and remove the quartz from the bottom material of the crucible.

[0040] S5: Rinse the silicon material obtained in step S4 with pure water.

[0041] S6: Clean the silicon material obtained in step S5 with a mixed acid of hydrofluoric acid and nitric acid. The mixing ratio of hydrofluoric acid to nitric acid is 3:1 (volume ratio).

[0042] The silicon material is cleaned using a mixed acid of hydrofluoric acid and nitric acid to remove metal ions. In step S5, most of the metal ions in the silicon material come from the quartz crucible. Therefore, the purer the silicon material obtained in step S4 (i.e., the lower the quartz content), the more exposed metal ions it contains. The better the removal effect of metal ions is achieved in step S6 when cleaning the silicon material with the mixed acid, thereby improving the purity of the final silicon material.

[0043] S7: Rinse the silicon material obtained in step S6 with pure water.

[0044] S8: Use pure water to ultrasonically clean the silicon material obtained in step S7, and then dry it to obtain pure silicon material.

[0045] The cleaning method for the bottom material of the monocrystalline silicon crucible in this application pre-treats the bottom material with water vapor before immersion in hydrofluoric acid, thereby increasing the surface silanol groups on the quartz surface. The silanol groups act as reaction centers to promote the reaction between quartz and hydrofluoric acid, increase the reaction rate, and thus save the time required for hydrofluoric acid immersion and improve the cleaning efficiency.

[0046] In some embodiments, in step S2, the volume percentage of water vapor in the first mixed gas is 0.5% to 1.5%.

[0047] Specifically, the volume percentage of water vapor in the first mixed gas can be 0.5%, 0.7%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, or any value between any two of the above ranges.

[0048] In some preferred embodiments, in step S2, the volume percentage of water vapor in the first mixed gas is 1%.

[0049] By controlling the volume ratio of water vapor in the first mixed gas, sufficient OH radicals can be provided during plasma pretreatment, thereby enabling the smooth generation of silanol groups on the quartz surface and improving the effectiveness of plasma pretreatment.

[0050] In some embodiments, in step S2, the flow rate of the first mixed gas is 60 sccm to 80 sccm.

[0051] Specifically, in practical applications, the flow rate of the first mixed gas can be 60 sccm, 65 sccm, 70 sccm, 75 sccm, 80 sccm, or any value between any two of the above ranges.

[0052] In some preferred embodiments, in step S2, the flow rate of the first mixed gas is 65 sccm to 70 sccm.

[0053] Specifically, in practical applications, the flow rate of the first mixed gas can be 65 sccm, 66 sccm, 67 sccm, 68 sccm, 69 sccm, 70 sccm, or any value between any two of the above ranges.

[0054] By controlling the flow rate of the first mixed gas, sufficient water vapor is provided to the reaction chamber during plasma pretreatment, thereby providing enough OH radicals to successfully generate silanol groups on the quartz surface and improve the effect of plasma pretreatment.

[0055] In some embodiments, the plasma pretreatment time in step S2 is 15 min to 30 min.

[0056] In some preferred embodiments, the plasma pretreatment time in step S2 is 20 min.

[0057] By controlling the plasma pretreatment time to 15-30 minutes, the effectiveness of the plasma pretreatment is ensured, resulting in a sufficient amount of silanol groups on the quartz surface. This further improves the reaction rate during the hydrofluoric acid immersion process and the dry etching process, thereby saving reaction time and improving cleaning efficiency.

[0058] In some embodiments, during step S2, the plasma generator operates at a voltage of 7–9 kV and a frequency of 15 kHz during plasma pretreatment. This configuration allows for the efficient decomposition of water molecules into OH radicals, H atoms, and other reactive particles during plasma pretreatment, enabling them to react with silicon atoms on the quartz surface.

[0059] Preferably, the cleaning method for the bottom material of the single crystal silicon crucible in this application further includes dry etching treatment of the bottom material between the plasma pretreatment step in step S2 and the acid soaking step in step S4.

[0060] Specifically, please refer to Figure 2 The cleaning method for the single-crystal silicon crucible bottom material of this application further includes step S3 between step S2 and step S4; in step S3, the reaction chamber is evacuated to prevent the silicon material from being oxidized. When the internal pressure of the reaction chamber drops to a first preset pressure range, a second mixed gas of nitrogen and hydrogen fluoride is introduced into the reaction chamber, and the internal pressure of the reaction chamber is maintained within the second preset pressure range, so as to use hydrogen fluoride gas to perform dry etching treatment on the crucible bottom material obtained in step S2 to obtain the second treated crucible bottom material.

[0061] Using hydrogen fluoride for dry etching of the crucible bottom material at high temperature increases the roughness of the quartz and the separation rate between the quartz and silicon. This provides a high specific surface area during hydrofluoric acid immersion of the crucible bottom material, further increasing the reaction rate between hydrofluoric acid and quartz, saving the time required for hydrofluoric acid immersion, and improving cleaning efficiency. The reaction mechanism of this dry etching is as follows: The reaction equation is: 6HF(ads) + SiO2 → H2SiF6(ads) + 2H2O.

[0062] In some embodiments, in step S3, the first preset pressure range is 5 Pa to 10 Pa.

[0063] Evacuate to 5-10 Pa to ensure the vacuum level in the reaction chamber and minimize the oxygen in the reaction chamber, thereby preventing the silicon material from being oxidized.

[0064] In some embodiments, in step S3, the second preset pressure range is 18 Pa to 22 Pa.

[0065] During the introduction of the second mixed gas, the amount of the second mixed gas introduced is controlled by maintaining the pressure in the reaction chamber at 18-22 Pa, thereby ensuring the effectiveness of dry etching.

[0066] In some embodiments, in step S3, the volume percentage of hydrogen fluoride in the second mixed gas is 5% to 10%.

[0067] In some preferred embodiments, in step S3, the volume percentage of hydrogen fluoride in the second mixed gas is 8%.

[0068] Specifically, in practical applications, the volume percentage of hydrogen fluoride in the second mixed gas can be 5%, 6%, 7%, 8%, 9%, 10%, or any value between any two of the above ranges.

[0069] By controlling the volume ratio of hydrogen fluoride in the second mixed gas, an appropriate amount of hydrogen fluoride is provided in the reaction chamber to facilitate a smooth reaction with the quartz, thereby increasing the surface roughness of the quartz and providing a high specific surface area for subsequent hydrofluoric acid immersion.

[0070] In some embodiments, the dry etching process in step S3 takes 10 to 15 hours.

[0071] In some preferred embodiments, the dry etching process in step S3 takes 12 hours.

[0072] By controlling the dry etching process time to 10–15 hours, the effectiveness of the dry etching process is ensured, allowing hydrogen fluoride gas to react with some of the quartz, thereby reducing the remaining quartz content in the crucible bottom material and maximizing the surface roughness of the quartz.

[0073] In some embodiments, in step S3, during the dry etching process, the plasma equipment heats the crucible bottom material to 500°C to 800°C.

[0074] In some preferred embodiments, in step S3, during the dry etching process, the plasma equipment heats the crucible bottom material to 500°C.

[0075] Specifically, in practical applications, during the dry etching process, the heating temperature can be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, or any value between any two of the above ranges.

[0076] 500°C is sufficient to meet the requirements, therefore, plasma equipment is preferred to heat the crucible bottom material to 500°C to save energy.

[0077] In some embodiments, in step S4, the temperature of the hydrofluoric acid solution is 55°C to 65°C.

[0078] In some preferred embodiments, the temperature of the hydrofluoric acid solution in step S4 is 60°C.

[0079] Specifically, in practical applications, the temperature of the hydrofluoric acid solution can be 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, or any value between any two of the above ranges.

[0080] In some embodiments, in step S4, the soaking time for the soaking treatment is 20h to 30h.

[0081] In some preferred embodiments, in step S4, the soaking time for the soaking treatment is 24 hours.

[0082] Specifically, in practical applications, the soaking time for immersion treatment is 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h, or any value between any two of the above ranges.

[0083] The following detailed embodiments illustrate the cleaning method for the bottom material of the monocrystalline silicon crucible of this application.

[0084] Example 1

[0085] The cleaning method for the bottom material of the monocrystalline silicon crucible in this embodiment includes the following steps:

[0086] S1, crush the bottom material of the crucible into particles ≥20mm, screen out silicon and quartz, and determine the bottom material of the crucible containing residual quartz as the bottom material to be processed.

[0087] S2, 50 kg of the crucible bottom material to be treated is placed in the reaction chamber of the plasma generator, and a first mixed gas of water vapor and argon is introduced into the reaction chamber to pre-treat the silicon crucible bottom material with plasma to obtain the first treated crucible bottom material; wherein, the volume ratio of water vapor in the first mixed gas is 1%, the flow rate of the first mixed gas is 70 sccm, the plasma treatment time is 20 min, and during the plasma pre-treatment process, the voltage of the plasma generator is 7-9 KV and the working frequency is 15 kHz.

[0088] S4, the treated crucible bottom material is transferred to a hydrofluoric acid solution (concentration of 49%) for immersion treatment to obtain silicon material, wherein the temperature of the hydrofluoric acid solution is 60℃ and the immersion time is 24h.

[0089] S5, Rinse the silicon material obtained in step S4 with pure water.

[0090] S6, the silicon material obtained in step S5 is cleaned with a mixed acid of hydrofluoric acid and nitric acid in a volume ratio of 3:1.

[0091] S7, Rinse the silicon material obtained in step S6 with pure water.

[0092] S8, use pure water to ultrasonically clean the silicon material obtained in step S7, and then dry it to obtain pure silicon material.

[0093] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 24 hours and 20 minutes. It should be noted that the total time in the embodiment and comparative example is the sum of the times for steps S1 to S4, and the processing time for steps S5 to S8 is relatively short and is not included.

[0094] Example 2

[0095] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in Embodiment 1. The crucible bottom material to be cleaned is from the same batch as that in Embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and Embodiment 1 is that the soaking time in step S4 is different.

[0096] Specifically, the soaking time in step S4 of this embodiment is 32 hours.

[0097] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 32 hours and 20 minutes.

[0098] Example 3

[0099] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in Embodiment 1. The crucible bottom material to be cleaned is from the same batch as that in Embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and Embodiment 1 is that the soaking time in step S4 is different.

[0100] Specifically, the soaking time in step S4 of this embodiment is 42 hours.

[0101] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 42 hours and 20 minutes.

[0102] Example 4

[0103] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in Embodiment 1. The crucible bottom material to be cleaned is from the same batch as that in Embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and Embodiment 1 is that the soaking time in step S4 is different.

[0104] Specifically, the soaking time in step S4 of this embodiment is 50 hours.

[0105] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 50 hours and 20 minutes.

[0106] Example 5

[0107] The cleaning method for the bottom material of the monocrystalline silicon crucible in this embodiment includes the following steps:

[0108] S1, the crucible bottom material is crushed into particles ≥20mm, and the crucible bottom material containing residual quartz is screened out as the crucible bottom material to be processed. The crucible bottom material in this embodiment is from the same batch as that in Example 1.

[0109] S2, 50 kg of the crucible bottom material to be treated is placed in the reaction chamber of the plasma generator, and a first mixed gas of water vapor and argon is introduced into the reaction chamber to pre-treat the silicon crucible bottom material with plasma to obtain the first treated crucible bottom material; wherein, the volume ratio of water vapor in the first mixed gas is 1%, the flow rate of the first mixed gas is 70 sccm, the plasma treatment time is 20 min, and during the plasma pre-treatment process, the voltage of the plasma generator is 7-9 KV and the working frequency is 15 kHz.

[0110] S3, firstly, the reaction chamber is evacuated. When the internal pressure of the reaction chamber drops to the first preset pressure range, a second mixed gas of nitrogen and hydrogen fluoride is introduced into the reaction chamber, and the internal pressure of the reaction chamber is maintained within the second preset pressure range. The crucible bottom material obtained in step S2 is then dry-etched using hydrogen fluoride gas to obtain the second-treated crucible bottom material. The first preset pressure range is 5 Pa to 10 Pa, the second preset pressure range is 18 Pa to 22 Pa, the volume percentage of hydrogen fluoride in the second mixed gas is 8%, the dry etching time is 12 hours, and during the dry etching process, the plasma equipment heats the crucible bottom material to 500°C.

[0111] S4, the treated crucible bottom material is transferred to a hydrofluoric acid solution (concentration of 49%) for immersion treatment to obtain silicon material, wherein the temperature of the hydrofluoric acid solution is 60℃ and the immersion time is 24h.

[0112] S5, Rinse the silicon material obtained in step S4 with pure water.

[0113] S6, use a mixed acid of hydrofluoric acid and nitric acid to clean the silicon material obtained in step S5.

[0114] S7, Rinse the silicon material obtained in step S6 with pure water.

[0115] S8, use pure water to ultrasonically clean the silicon material obtained in step S7, and then dry it to obtain pure silicon material.

[0116] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 36 hours and 20 minutes.

[0117] Example 6

[0118] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the volume ratio of water vapor in the first mixed gas in step S2 is different.

[0119] Specifically, in step S2 of this embodiment, the volume percentage of water vapor in the first mixed gas is 0.5%.

[0120] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0121] Example 7

[0122] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the volume ratio of water vapor in the first mixed gas in step S2 is different.

[0123] Specifically, in step S2 of this embodiment, the volume percentage of water vapor in the first mixed gas is 1.5%.

[0124] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0125] Example 8

[0126] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the volume ratio of water vapor in the first mixed gas in step S2 is different.

[0127] Specifically, in step S2 of this embodiment, the volume percentage of water vapor in the first mixed gas is 0.1%.

[0128] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0129] Example 9

[0130] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the volume ratio of water vapor in the first mixed gas in step S2 is different.

[0131] Specifically, in step S2 of this embodiment, the volume percentage of water vapor in the first mixed gas is 2%.

[0132] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0133] Example 10

[0134] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the flow rate of the first mixed gas in step S2 is different.

[0135] Specifically, in step S2 of this embodiment, the flow rate of the first mixed gas is 60 sccm.

[0136] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0137] Example 11

[0138] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the flow rate of the first mixed gas in step S2 is different.

[0139] Specifically, in step S2 of this embodiment, the flow rate of the first mixed gas is 65 sccm.

[0140] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0141] Example 12

[0142] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the flow rate of the first mixed gas in step S2 is different.

[0143] Specifically, in step S2 of this embodiment, the flow rate of the first mixed gas is 68 sccm.

[0144] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0145] Example 13

[0146] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the flow rate of the first mixed gas in step S2 is different.

[0147] Specifically, in step S2 of this embodiment, the flow rate of the first mixed gas is 75 sccm.

[0148] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0149] Example 14

[0150] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the flow rate of the first mixed gas in step S2 is different.

[0151] Specifically, in step S2 of this embodiment, the flow rate of the first mixed gas is 80 sccm.

[0152] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0153] Example 15

[0154] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the plasma pretreatment time in step S2 is different.

[0155] Specifically, in step S2 of this embodiment, the plasma pretreatment time is 15 minutes.

[0156] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 36 hours and 15 minutes.

[0157] Example 16

[0158] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the plasma pretreatment time in step S2 is different.

[0159] Specifically, in step S2 of this embodiment, the plasma pretreatment time is 30 minutes.

[0160] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 36 hours and 30 minutes.

[0161] Example 17

[0162] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the plasma pretreatment time in step S2 is different.

[0163] Specifically, in step S2 of this embodiment, the plasma pretreatment time is 40 minutes.

[0164] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 36 hours and 40 minutes.

[0165] Example 18

[0166] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the plasma pretreatment time in step S2 is different.

[0167] Specifically, in step S2 of this embodiment, the plasma pretreatment time is 10 minutes.

[0168] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 36 hours and 10 minutes.

[0169] Example 19

[0170] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the volume ratio of hydrogen fluoride in the second mixed gas in step S3 is different.

[0171] Specifically, in step S3 of this embodiment, the volume percentage of hydrogen fluoride in the second mixed gas is 5%.

[0172] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0173] Example 20

[0174] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the volume ratio of hydrogen fluoride in the second mixed gas in step S3 is different.

[0175] Specifically, in step S3 of this embodiment, the volume percentage of hydrogen fluoride in the second mixed gas is 10%.

[0176] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0177] Example 21

[0178] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the volume ratio of hydrogen fluoride in the second mixed gas in step S3 is different.

[0179] Specifically, in step S3 of this embodiment, the volume percentage of hydrogen fluoride in the second mixed gas is 15%.

[0180] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0181] Example 22

[0182] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the volume ratio of hydrogen fluoride in the second mixed gas in step S3 is different.

[0183] Specifically, in step S3 of this embodiment, the volume percentage of hydrogen fluoride in the second mixed gas is 3%.

[0184] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0185] Example 23

[0186] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the dry etching process in step S3 is different.

[0187] Specifically, in step S3 of this embodiment, the dry etching process takes 10 hours.

[0188] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 34 hours and 20 minutes.

[0189] Example 24

[0190] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the dry etching process in step S3 is different.

[0191] Specifically, in step S3 of this embodiment, the dry etching process takes 15 hours.

[0192] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 39 hours and 20 minutes.

[0193] Example 25

[0194] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the dry etching process in step S3 is different.

[0195] Specifically, in step S3 of this embodiment, the dry etching process takes 8 hours.

[0196] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 32 hours and 20 minutes.

[0197] Example 26

[0198] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the heating temperature in the dry etching process in step S3 is different.

[0199] Specifically, in step S3 of this embodiment, the heating temperature during the dry etching process is 400°C.

[0200] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0201] Example 27

[0202] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the heating temperature in the dry etching process in step S3 is different.

[0203] Specifically, in step S3 of this embodiment, the heating temperature during the dry etching process is 600°C.

[0204] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0205] Example 28

[0206] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the heating temperature in the dry etching process in step S3 is different.

[0207] Specifically, in step S3 of this embodiment, the heating temperature during the dry etching process is 800°C.

[0208] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is the same as in Embodiment 5, which is 36 hours and 20 minutes.

[0209] Example 29

[0210] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the soaking time in step S4 is different.

[0211] Specifically, in step S4 of this embodiment, the soaking time is 20 hours.

[0212] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 32 hours and 20 minutes.

[0213] Example 30

[0214] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the soaking time in step S4 is different.

[0215] Specifically, in step S4 of this embodiment, the soaking time is 25 hours.

[0216] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 37 hours and 20 minutes.

[0217] Example 31

[0218] The cleaning method for the single-crystal silicon crucible bottom material in this embodiment is the same as that in embodiment 5. The crucible bottom material to be cleaned is from the same batch as that in embodiment 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this embodiment and embodiment 5 is that the soaking time in step S4 is different.

[0219] Specifically, in step S4 of this embodiment, the soaking time is 30 hours.

[0220] In this embodiment, the total time for cleaning the bottom material of the monocrystalline silicon crucible is 42 hours and 20 minutes.

[0221] Comparative Example 1

[0222] The cleaning method for the bottom material of the monocrystalline silicon crucible in this comparative example includes the following steps:

[0223] S1, the crucible bottom material is crushed into particles ≥20mm, and the crucible bottom material containing residual quartz is screened out as the crucible bottom material to be processed. The crucible bottom material in this embodiment is from the same batch as that in Example 1.

[0224] S4. 50 kg of the bottom material to be treated is placed in a hydrofluoric acid solution for immersion treatment to obtain silicon material. The temperature of the hydrofluoric acid solution is 60℃ and the immersion time is 24 h.

[0225] S5, Rinse the silicon material obtained in step S4 with pure water.

[0226] S6, use a mixed acid of hydrofluoric acid and nitric acid to clean the silicon material obtained in step S5.

[0227] S7, Rinse the silicon material obtained in step S6 with pure water.

[0228] S8, use pure water to ultrasonically clean the silicon material obtained in step S7, and then dry it to obtain pure silicon material.

[0229] Comparative Example 2

[0230] The cleaning method for the single-crystal silicon crucible bottom material in this comparative example is the same as that in Comparative Example 1. The crucible bottom material cleaned is from the same batch as that in Example 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this example and Comparative Example 1 is that the soaking time in step S4 is different.

[0231] Specifically, in step S4 of this comparative example, the soaking time is 40 hours.

[0232] Comparative Example 3

[0233] The cleaning method for the single-crystal silicon crucible bottom material in this comparative example is the same as that in Comparative Example 1. The crucible bottom material cleaned is from the same batch as that in Example 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this example and Comparative Example 1 is that the soaking time in step S4 is different.

[0234] Specifically, in step S4 of this comparative example, the soaking time is 50 hours.

[0235] Comparative Example 4

[0236] The cleaning method for the single-crystal silicon crucible bottom material in this comparative example is the same as that in Comparative Example 1. The crucible bottom material cleaned is from the same batch as that in Example 1. The mass of the crucible bottom material to be cleaned is 50 kg. The difference between this example and Comparative Example 1 is that the soaking time in step S4 is different.

[0237] Specifically, in step S4 of this comparative example, the soaking time is 60 hours.

[0238] Test case

[0239] The total content of metal impurities on the surface of the silicon materials obtained in the examples and comparative examples was detected by inductively coupled plasma mass spectrometry. The content of various metal impurities was used to determine whether the obtained silicon materials met the solar energy grade standard. When the total content of metal impurities was ≤8ng / g, the silicon materials were determined to meet the solar energy grade standard. The test results are shown in Table 1.

[0240] Table 1. Metal detection results of silicon materials obtained from the examples and comparative examples.

[0241] From the experimental data above, we can see that:

[0242] The experimental data from Examples 1-31 and Comparative Examples 1-4 show that the silicon materials obtained from Examples 3-31 and Comparative Examples 3 and 4 have low metal content, which meets the solar energy grade standard. The silicon materials obtained from Examples 1, 2, 1 and 2 have high metal content, which does not meet the solar energy grade standard.

[0243] 1. Comparing Examples 3 and 4 with Comparative Examples 3 and 4, the total processing time of Examples 3 and 4 is 7 hours less than that of Comparative Examples 3 and 4. This demonstrates that, while obtaining silicon material that meets the same solar-grade standards, pre-treating the crucible bottom material with steam before immersing it in hydrofluoric acid solution can effectively shorten the immersion time, thereby increasing the reaction rate, saving total reaction time, and improving cleaning efficiency. Therefore, the first embodiment of this application can effectively shorten the cleaning time and improve cleaning efficiency.

[0244] 2. Comparing Examples 5 to 31 with Examples 3 and 4, Examples 5 to 31 have a total processing time 10 hours shorter than Examples 3 and 4. This demonstrates that, while obtaining silicon material that meets the same solar-grade standards, dry etching of the crucible bottom material using hydrogen fluoride at high temperature before immersing it in hydrofluoric acid solution and between plasma pretreatment with steam can further shorten the time required for immersion, thereby increasing the reaction rate, saving total reaction time, and improving cleaning efficiency. Therefore, the second embodiment of this application can further shorten the cleaning time and further improve cleaning efficiency compared to the first embodiment.

[0245] 3. Comparing Examples 5 to 9, as the volume percentage of water vapor in the first mixed gas increases, the total content of detected metal impurities gradually decreases. Furthermore, the results of Example 9 are not significantly different from those of Example 7, and the total content of metal impurities in Example 8 is close to the limit of the solar-grade standard. Therefore, to improve the cleaning effect, it is preferable to make the volume percentage of water vapor in the first mixed gas 0.5% to 1.5%, and most preferably, the volume percentage of water vapor in the first mixed gas is 1%.

[0246] 4. Comparing Examples 5 and Examples 10-14, as the flow rate of the first mixed gas increases, the total content of detected metal impurities first decreases and then slightly increases. This shows that only when the flow rate of the first mixed gas is kept within a certain range can a better treatment effect be guaranteed. Too little or too much flow rate of the first mixed gas will affect the effect of plasma pretreatment. Therefore, it is preferable to control the flow rate of the first mixed gas to 60 sccm to 80 sccm, and most preferably to control the flow rate of the first mixed gas to 65 sccm to 70 sccm.

[0247] 5. Comparing Example 5 with Examples 15-18, as the plasma pretreatment time increases, the total content of detected metal impurities first gradually decreases and then slightly increases. It can be seen that only when the plasma pretreatment time is controlled within a certain range can a better treatment effect be guaranteed. Therefore, it is preferable to make the plasma pretreatment time 15 min to 30 min, and more preferably to make the plasma pretreatment time 15 min to 20 min.

[0248] 6. Comparing Examples 5 and Examples 19-22, as the volume percentage of hydrogen fluoride in the second mixed gas increases, the total content of detected metal impurities first decreases and then increases. Therefore, it is preferable to make the volume percentage of hydrogen fluoride in the second mixed gas 5% to 10%, and more preferably to make the volume percentage of hydrogen fluoride in the second mixed gas 5% to 8%.

[0249] 7. Comparing Example 5 with Examples 23-25, the total content of detected metal impurities decreases as the dry etching time increases. Therefore, it is preferable to make the dry etching time 10h-15h.

[0250] 8. Comparing Examples 5 and Examples 26-28, when the heating temperature during dry etching is 400°C, the processing effect is worse than that at 500°C, 600°C and 800°C. Therefore, it is preferable to set the heating temperature to 500-800°C, and most preferably to set the heating temperature to 500°C.

[0251] 9. Comparing Examples 5 and Examples 29-31, the total content of metal impurities in Examples 5 and Examples 29-31 is similar. Therefore, in practical applications, it is preferable to soak for 20-30 hours, and more preferably to soak for 20-24 hours.

[0252] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for cleaning the bottom material of a monocrystalline silicon crucible, comprising, in sequence, acid soaking, mixed acid cleaning, and water washing, characterized in that, Prior to the acid soaking step, the cleaning method further includes plasma pretreatment of the crucible bottom material to be treated.

2. The method for cleaning the bottom material of a single-crystal silicon crucible according to claim 1, wherein the plasma pretreatment includes: The crucible bottom material to be treated is placed in the reaction chamber of the plasma generator, and a first mixed gas of water vapor and argon is introduced into the reaction chamber to perform plasma pretreatment on the crucible bottom material to be treated.

3. The method for cleaning the bottom material of a single-crystal silicon crucible according to claim 2, characterized in that, Between the plasma pretreatment step and the acid immersion step, a dry etching process is also performed on the bottom material of the crucible.

4. The method for cleaning the bottom material of a single-crystal silicon crucible according to claim 3, characterized in that, The dry etching process includes: evacuating the reaction chamber, introducing a second mixed gas of nitrogen and hydrogen fluoride into the reaction chamber when the internal pressure of the reaction chamber drops to a first preset pressure range, and maintaining the internal pressure of the reaction chamber within the second preset pressure range, so as to perform dry etching on the crucible bottom material using hydrogen fluoride gas.

5. The method for cleaning the bottom material of a single-crystal silicon crucible according to claim 2, characterized in that, During the plasma pretreatment process, the water vapor accounts for 0.5% to 1.5% of the volume of the first mixed gas; And / or, during the plasma pretreatment process, the flow rate of the first mixed gas is 60 sccm to 80 sccm; And / or, during the plasma pretreatment process, the plasma pretreatment time is 15 min to 30 min; And / or, during the plasma pretreatment process, the voltage of the plasma generator is 7-9 kV and the operating frequency is 15 kHz.

6. The method for cleaning the bottom material of a single-crystal silicon crucible according to claim 5, characterized in that, During the plasma pretreatment process, the water vapor accounts for 1% of the volume of the first mixed gas; And / or, during the plasma pretreatment process, the flow rate of the first mixed gas is 65 sccm to 70 sccm; And / or, during the plasma pretreatment process, the plasma pretreatment time is 20 minutes.

7. The method for cleaning the bottom material of a single-crystal silicon crucible according to claim 4, characterized in that, During the dry etching process, the first preset pressure range is 5 Pa to 10 Pa; And / or, during the dry etching process, the second preset pressure range is 18 Pa to 22 Pa; And / or, during the dry etching process, the hydrogen fluoride accounts for 5% to 10% of the volume of the second mixed gas; And / or, during the dry etching process, the dry etching time is 10h to 15h.

8. The method for cleaning the bottom material of a single-crystal silicon crucible according to claim 7, characterized in that, During the dry etching process, the hydrogen fluoride accounts for 8% of the volume of the second mixed gas; And / or, during the dry etching process, the dry etching time is 12 hours; And / or, during the dry etching process, the plasma equipment heats the crucible bottom material to 500°C to 800°C.

9. The method for cleaning the bottom material of a single-crystal silicon crucible according to any one of claims 1 to 8, characterized in that, The acid soaking includes: soaking the crucible bottom material in a hydrofluoric acid solution; And / or, a water washing step may be included between the acid soaking step and the mixed acid cleaning step.

10. The method for cleaning the bottom material of a single-crystal silicon crucible according to claim 9, characterized in that, During the acid soaking process, the temperature of the hydrofluoric acid solution is 55℃~65℃; And / or, during the acid soaking process, the soaking time of the soaking treatment is 20h to 30h.

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