Graphite boat dry cleaning method

Abstract

The invention discloses a graphite boat dry cleaning method, a coating film on the surface of a graphite boat comprises at least one of a silicon-based thin film, a silicon oxide thin film, a silicon nitride thin film and a silicon oxynitride thin film, and the method comprises the following steps: introducing cleaning gas into a cleaning cavity to carry out radio frequency dissociation on the cleaning gas, the cleaning gas contains CO2, O2 and NF3, so that the coating film on the surface of the graphite boat can be etched and cleaned. According to the method, the coating film on the surface of the graphite boat can be effectively etched and cleaned, the cleaning efficiency is high, and under the condition that the same graphite boat is cleaned, the NF3 used by the method is far less than that used by a traditional method, so that the production cost is remarkably reduced.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a dry cleaning method for graphite boats. Background Technology

[0002] In existing crystalline silicon solar cell manufacturing technologies, solar cells are placed in a graphite boat and coated using PECVD. PECVD has high requirements for electric field strength and stability. During the coating process, a film continuously accumulates on the surface of the graphite boat. Because the film grown on the graphite boat surface has a certain resistivity, once it accumulates to a certain thickness, it is equivalent to a resistor in series, affecting the PECVD circuit current and voltage, and thus the film formation rate and uniformity. Therefore, to ensure coating quality, the surface film of the graphite boat must be cleaned off after a certain period of use. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one objective of this invention is to provide a dry cleaning method for graphite boats. This method can effectively etch and clean the coating on the surface of graphite boats with high cleaning efficiency. When cleaning the same graphite boat, it uses significantly less NF3 than traditional methods, thereby significantly reducing production costs.

[0004] In one aspect of the present invention, a dry cleaning method for a graphite boat is provided. According to an embodiment of the present invention, the coating on the surface of the graphite boat includes at least one of a silicon-based thin film, a silicon oxide thin film, a silicon nitride thin film, and a silicon oxynitride thin film. The method includes: introducing a cleaning gas into a cleaning chamber to perform radio frequency dissociation on the cleaning gas, so as to etch and clean the coating on the surface of the graphite boat; the cleaning gas includes CO2, O2, and NF3.

[0005] According to the dry cleaning method for graphite boats of the present invention described above, a cleaning gas is introduced into a cleaning chamber and subjected to radio frequency dissociation to etch and clean the coating on the surface of the graphite boat. The cleaning gas includes CO2, O2, and NF3. The inventors have discovered that when etching and cleaning the coating on the surface of a graphite boat, mixing CO2 and / or O2 into the conventional etching gas NF3 can significantly improve the cleaning efficiency of the coating on the graphite boat surface and reduce cleaning costs. Specifically, under radio frequency discharge, NF3 dissociates as follows: NF3 → NF2 (plasma state) + F (plasma state), NF2 → NF (plasma state) + F (plasma state), NF (plasma state) + NF (plasma state) → N2 + 2F (plasma state). However, in the above process, NF (plasma state) and NF2 (plasma state) will combine and react to generate gaseous N2 and F2. The reaction process is as follows: NF (plasma state) + NF2 (plasma state) → N2 + F2 + F (plasma state), which reduces the concentration of F (plasma state) in the dry etching cavity and slows down the plasma cleaning rate. If O2 is mixed into NF3, NF2 and NF react with O2 to generate active NF, OF, and F. The specific reactions are as follows: O2 + 2NF2 → 2NF + 2OF (plasma state), O2 + 2NF → 2NO + 2F (plasma state). This inhibits the decrease in the concentration of active F ions caused by the combination of NF2 and NF, and improves the etching and cleaning rate. At the same time, with the same amount of NF3, more graphite boats can be etched and cleaned. The cost of O2 is much lower than that of NF3, thus significantly reducing the production cost. If CO2 is mixed into NF3, radio frequency ionization can promote the reaction between NF3 and CO2 to generate CO and F free radicals. These CO and F free radicals further react to generate in-situ COF and COF2. COF and COF2 can effectively clean the coating on the graphite boat surface. The specific reactions are as follows: NF3 + CO2 → CO (plasma state) + F (plasma state) + NO, CO (plasma state) + F (plasma state) → COF (plasma state) + COF2 (atomic state). The entire reaction proceeds in the forward direction, promoting the dissociation of NF3, thereby improving cleaning efficiency, reducing the NF3 content in the exhaust gas, and lowering production costs. Therefore, this method can effectively etch and clean the coating on the graphite boat surface with high efficiency. When cleaning the same graphite boat, far less NF3 is used compared to traditional methods, thus significantly reducing production costs.

[0006] In addition, the graphite boat dry cleaning method according to the above embodiments of the present invention may also have the following technical features:

[0007] In some embodiments of the present invention, the cleaning gas further includes an inert gas.

[0008] In some embodiments of the present invention, when the coating on the surface of the graphite boat is a silicon-based thin film and / or a silicon oxide thin film, the cleaning gas includes NF3 and CO2. This improves the etching and cleaning efficiency of the coating on the graphite boat surface.

[0009] In some embodiments of the present invention, when the coating on the surface of the graphite boat is a silicon nitride thin film and / or a silicon oxynitride thin film, the cleaning gas includes NF3 and O2. This improves the etching and cleaning efficiency of the coating on the graphite boat surface and reduces costs.

[0010] In some embodiments of the present invention, NF3 and CO2 are introduced into the cleaning chamber for radio frequency dissociation cleaning, with the volumetric flow rate of NF3 being 500 sccm to 2000 sccm and the volumetric flow rate of CO2 being 300 sccm to 2000 sccm. This improves the etching and cleaning efficiency of the coating on the graphite boat surface.

[0011] In some embodiments of the present invention, NF3 and O2 are introduced into the cleaning chamber for radio frequency dissociation cleaning, with the volumetric flow rate of NF3 being 500 sccm to 2000 sccm and the volumetric flow rate of CO2 being 400 sccm to 2000 sccm. This improves the etching and cleaning efficiency of the coating on the graphite boat surface.

[0012] In some embodiments of the present invention, the temperature of the cleaning chamber is 100°C to 400°C, and the power of the radio frequency is 4000W to 8000W. This improves the etching and cleaning efficiency of the coating on the graphite boat surface.

[0013] In some embodiments of the present invention, the volumetric flow rate of the inert gas is no greater than 3000 sccm. This improves the etching and cleaning efficiency of the coating on the graphite boat surface.

[0014] In some embodiments of the present invention, the radio frequency dissociation process includes: (1) introducing the cleaning gas into the cleaning chamber for a first radio frequency dissociation cleaning to remove 60% to 80% of the coating thickness on the graphite boat; and (2) reducing the radio frequency power for a second radio frequency dissociation cleaning to remove the remaining 20% ​​to 40% of the coating thickness on the graphite boat. This avoids damage to the surface of the graphite boat during the radio frequency dissociation cleaning process.

[0015] In some embodiments of the present invention, the power of the second radio frequency dissociation is 100W to 1000W lower than the power of the first radio frequency dissociation. This avoids damage to the surface of the graphite boat during the radio frequency dissociation cleaning process.

[0016] In some embodiments of the present invention, the method further includes: evacuating the cleaning chamber for the first time before introducing the cleaning gas into the cleaning chamber.

[0017] In some embodiments of the present invention, after the coating on the surface of the graphite boat is etched and cleaned, the cleaning chamber is evacuated a second time in order to discharge the reaction waste gas.

[0018] In some embodiments of the present invention, the vacuum pressure of the cleaning chamber after the first vacuuming is 1000 mtor to 3000 mtor.

[0019] In some embodiments of the present invention, the vacuum pressure of the cleaning chamber after the second vacuuming is 0 mtor to 20 mtor.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0022] Figure 1 This is a schematic diagram of the dry cleaning method for graphite boats according to an embodiment of the present invention. Detailed Implementation

[0023] The embodiments of the present invention are described in detail below, and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0024] Firstly, this invention proposes a dry cleaning method for graphite boats. (Reference) Figure 1 According to an embodiment of the present invention, the coating on the surface of the graphite boat includes at least one of silicon-based thin film, silicon oxide thin film, silicon nitride thin film and silicon oxynitride thin film. The method includes: introducing a cleaning gas into a cleaning chamber to perform radio frequency dissociation on the cleaning gas in order to etch and clean the coating on the surface of the graphite boat. The cleaning gas includes CO2, O2 and NF3.

[0025] According to the dry cleaning method for graphite boats of the above embodiments of the present invention, a cleaning gas is introduced into a cleaning chamber and subjected to radio frequency dissociation to etch and clean the coating on the surface of the graphite boat. The cleaning gas includes CO2, O2, and NF3. The inventors have discovered that when etching and cleaning the coating on the surface of a graphite boat, mixing CO2 and / or O2 into the conventional etching gas NF3 can significantly improve the cleaning efficiency of the coating on the graphite boat surface and reduce the cleaning cost. Specifically, the dissociation process of NF3 under radio frequency discharge is as follows:

[0026] NF3 → NF2 (plasma state) + F (plasma state);

[0027] NF2 → NF (plasma state) + F (plasma state);

[0028] NF (plasma) + NF (plasma) → N2 + 2F (plasma).

[0029] However, during the above process, NF (plasma state) and NF2 (plasma state) react to generate gaseous N2 and F2, as follows: NF (plasma state) + NF2 (plasma state) → N2 + F2 + F (plasma state). This reduces the concentration of F (plasma state) in the dry etching chamber and slows down the plasma cleaning rate. If O2 is mixed into NF3, NF2 and NF react with O2 to generate active NF, OF, and F, as follows: O2 + NF2 → NF + OF (plasma state), O2 + NF → NO + F (plasma state). This suppresses the decrease in the concentration of active F ions caused by the combination of NF2 and NF, increases the etching cleaning rate, and allows for the etching and cleaning of more graphite boats with the same amount of NF3. Furthermore, the cost of O2 is much lower than that of NF3, thus significantly reducing production costs. If CO2 is mixed into NF3, radio frequency ionization can promote the reaction between NF3 and CO2 to generate CO and F free radicals. These CO and F free radicals further react to generate in-situ COF and COF2. COF and COF2 can effectively clean the coating on the graphite boat surface. The specific reactions are as follows: NF3 + CO2 → CO (plasma state) + F (plasma state) + NO (plasma state), CO (plasma state) + F (plasma state) → COF + COF2 (atomic state). The entire reaction proceeds in the forward direction, promoting the dissociation of NF3, thereby improving cleaning efficiency, reducing the NF3 content in the exhaust gas, and lowering production costs. Therefore, this method can effectively etch and clean the coating on the graphite boat surface with high efficiency. When cleaning the same graphite boat, far less NF3 is used compared to traditional methods, thus significantly reducing production costs.

[0030] It should be noted that silicon-based thin films refer to thin films containing only silicon, silicon oxide thin films refer to thin films containing both oxygen and silicon, silicon nitride thin films refer to thin films containing both nitrogen and silicon, and silicon oxynitride thin films refer to thin films containing nitrogen, silicon, and oxygen. Those skilled in the art will understand that the cleaning time for the coating on the graphite boat surface is directly proportional to the coating thickness and inversely proportional to the etching and cleaning time. After a period of cleaning, the graphite boat can be removed to observe whether the coating is clean, or existing testing equipment can be used to test the coating to determine whether it is clean.

[0031] Those skilled in the art will understand that each silicon wafer deposition uses a different gas, thus forming a film layer with the same composition as the silicon wafer deposition on the graphite boat surface. When a different gas is used for silicon wafer deposition, a film layer of a different composition will continue to accumulate on the graphite boat surface. Therefore, multilayer films of different compositions can be formed on the graphite boat surface. The most common types are silicon-based films, silicon oxide films, silicon nitride films, or silicon oxynitride films. The method of this application can effectively etch and clean the aforementioned common films. For example, when the silicon wafer deposition uses SiH4 gas, a silicon-based film is formed; when the silicon wafer deposition uses SiH4 and N2O gas, a silicon oxide film is formed; when the silicon wafer deposition uses SiH4 and NH3 gas, a silicon nitride film is formed; and when the silicon wafer deposition uses SiH4, NH3, and N2O gas, a silicon oxynitride film is formed.

[0032] According to embodiments of the present invention, the cleaning gas further includes an inert gas. Further, the volumetric flow rate of the inert gas is no greater than 3000 sccm. For example, the volumetric flow rate of the inert gas is 0 sccm, 500 sccm, 1000 sccm, 1500 sccm, 2000 sccm, 2500 sccm, 3000 sccm, etc. The inventors have found that introducing an inert gas can make the cleaning and etching reaction gas mix more uniformly with the graphite boat, and can also increase the flow rate and promptly remove reaction byproducts. However, introducing too much inert gas reduces the total reactant concentration, which is detrimental to improving the cleaning rate of the graphite boat. Therefore, introducing an inert gas into the cleaning gas, with a volumetric flow rate no greater than 3000 sccm, can effectively improve the cleaning rate and cleaning effect.

[0033] According to embodiments of the present invention, the coating on the surface of the graphite boat is a silicon-based thin film and / or a silicon oxide thin film, and the cleaning gas includes NF3 and CO2. The inventors discovered that under radio frequency ionization, NF3 and CO2 can react to generate CO and F free radicals. These CO and F free radicals further react to generate in-situ COF and COF2. COF and COF2 readily react with the silicon-based thin film and the silicon oxide thin film to generate a gaseous mixture of SiF4, CO2, and CO, thereby effectively etching and cleaning the silicon-based thin film and silicon oxide thin film on the surface of the graphite boat, significantly improving the etching and cleaning efficiency of the coating on the graphite boat surface.

[0034] According to embodiments of the present invention, NF3 and CO2 are introduced into the cleaning chamber for radiofrequency dissociation cleaning. The volumetric flow rate of NF3 is 500 sccm to 2000 sccm, and the volumetric flow rate of CO2 is 300 sccm to 2000 sccm. For example, the volumetric flow rates of NF3 are 500 sccm, 700 sccm, 900 sccm, 1100 sccm, 1300 sccm, 1500 sccm, 1700 sccm, 1800 sccm, 2000 sccm, etc.; and the volumetric flow rates of CO2 are 300 sccm, 500 sccm, 700 sccm, 900 sccm, 1100 sccm, 1300 sccm, 1500 sccm, 1700 sccm, 1900 sccm, 2000 sccm, etc. Preferably, the volumetric flow rate ratio of NF3 to CO2 is 1:1, which yields the best cleaning effect. The flow rate of the reaction gas is adjusted based on the size of the cleaning chamber and the actual cleaning effect. Ultimately, controlling the flow rate of the reaction gas within the above range can improve the etching and cleaning efficiency of the coating on the graphite boat surface.

[0035] According to embodiments of the present invention, the coating on the surface of the graphite boat is a silicon nitride thin film and / or a silicon oxynitride thin film, and the cleaning gas includes NF3 and O2. The inventors have discovered that since the etching and cleaning rate of silicon nitride and silicon oxynitride thin films is mainly related to the concentration of plasma-state F, adding oxygen can promote the ionization of plasma-state F when cleaning graphite boats with silicon nitride or silicon oxynitride thin films, thereby improving the etching and cleaning efficiency of the coating on the graphite boat surface and reducing costs.

[0036] According to an embodiment of the present invention, NF3 and O2 are introduced into the cleaning chamber for radio frequency dissociation cleaning. The volumetric flow rate of NF3 is 500 sccm to 2000 sccm, and the volumetric flow rate of O2 is 400 sccm to 2000 sccm. For example, the volumetric flow rates of NF3 are 500 sccm, 700 sccm, 900 sccm, 1100 sccm, 1300 sccm, 1500 sccm, 1700 sccm, 1800 sccm, 2000 sccm, etc.; and the volumetric flow rates of O2 are 400 sccm, 600 sccm, 800 sccm, 1000 sccm, 1200 sccm, 1400 sccm, 1600 sccm, 1800 sccm, 2000 sccm, etc. The optimal volumetric flow rate ratio of NF3 to O2 is 1:1. Based on atomic ratios, one NF3 ion produces one NF or one NF2 ion, and one NF or NF2 ion consumes one O ion. Therefore, theoretically, the NF3 to O2 volumetric flow rate ratio should be 2:1. However, considering that excess O2 can promote the production of F ions, a practical NF3 to O2 volumetric flow rate ratio of 1:1 is optimal. Simultaneously, the reaction gas flow rates are adjusted based on the size of the cleaning chamber and the actual cleaning effect. Controlling the NF3 and O2 volumetric flow rates within the above range achieves the best balance between cleaning rate and graphite boat lifespan.

[0037] According to embodiments of the present invention, the temperature of the cleaning chamber is 100℃~400℃, and the power of the radio frequency (RF) is 4000W~8000W. For example, the cleaning chamber temperatures are 100℃, 150℃, 200℃, 250℃, 300℃, 350℃, and 400℃; the RF power is 4000W, 5000W, 6000W, 7000W, and 8000W. The inventors have found that the higher the temperature of the cleaning chamber, the faster the reaction rate, but the graphite boat (C) is more easily oxidized, thus affecting the lifespan of the graphite boat; the higher the RF power, the faster the reaction rate, but the RF also has a certain etching effect on the surface of the graphite boat (C), affecting the lifespan of the graphite boat. In practical use, by controlling the temperature of the cleaning chamber and the RF power within the above ranges according to different graphite boat materials, surface film thickness, and balancing the lifespan of the graphite boat and the cleaning rate, the etching and cleaning efficiency of the graphite boat surface coating can be improved, and the lifespan of the graphite boat can be extended.

[0038] According to an embodiment of the present invention, the radio frequency (RF) dissociation process includes: (1) introducing the cleaning gas into the cleaning chamber for a first RF dissociation cleaning to remove 60%–80% of the coating thickness on the graphite boat; and (2) reducing the RF power for a second RF dissociation cleaning to remove the remaining 20%–40% of the coating thickness on the graphite boat. The inventors have found that by using a first RF dissociation etching cleaning of 60%–80% of the coating thickness, and then using a second RF dissociation etching cleaning with a lower power than the first, the remaining 20%–40% of the coating thickness can be cleaned. This avoids damage to the graphite boat caused by continuously using high power during the RF dissociation cleaning process, which would otherwise occur when etching reaches the graphite boat surface. Furthermore, the power of the second RF dissociation is 100W–1000W lower than the power of the first RF dissociation. Therefore, damage to the graphite boat surface during the RF dissociation cleaning process can be avoided.

[0039] According to an embodiment of the present invention, the method further includes: evacuating the cleaning chamber for the first time before introducing the cleaning gas. By evacuating the cleaning chamber for the first time, air inside the chamber can be expelled, and the gas flow rate can be increased under low pressure to meet the reaction conditions for plasma etching cleaning. Further, the vacuum pressure of the cleaning chamber after the first evacuation is 1000 mtor to 3000 mtor. Simultaneously, the cleaning chamber is heated during the first evacuation. The specific temperature range can be selected by those skilled in the art based on the actual object being cleaned and the process, and will not be elaborated here.

[0040] According to an embodiment of the present invention, the method further includes: after etching and cleaning the coating on the surface of the graphite boat, a second vacuum is applied to the cleaning chamber to remove the waste gas generated by the etching and cleaning reaction. Further, the vacuum pressure of the cleaning chamber after the second vacuum is 0 mtor to 20 mtor, which allows for the removal of byproducts such as plasma, nitrogen oxides, fluorine plasma, and fluorides from the chamber after cleaning, preventing them from escaping into the air and causing problems such as fire or pollution when the chamber is opened.

[0041] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0042] Example 1

[0043] A mixed gas of NF3, O2, and Ar was used to clean the silicon nitride and silicon oxynitride films on the surface of a graphite boat.

[0044] (1) The graphite boat to be cleaned, and the depth of the electrode rod inserted into the graphite boat is adjusted;

[0045] (2) Set the cleaning chamber temperature to 500℃, and heat the chamber until it stabilizes at that temperature;

[0046] (3) Purge with 8000 sccm N2 for 60 seconds, then reduce the chamber pressure to 50 mtor to remove air from the chamber.

[0047] (4) Evacuate the cleaning chamber to a vacuum pressure of 2000 mtor;

[0048] (5) Introduce 750 sccm NF3, 600 sccm O2, and 2500 sccm Ar into the cleaning chamber. The reaction temperature is 350℃, the radio frequency power is 6500W, the duty cycle is 1:2, and the cleaning time is 8000s to achieve efficient cleaning of silicon nitride film and silicon oxynitride film on the surface of graphite boat.

[0049] (6) Evacuate the cleaning chamber to 10 mtor to remove excess byproducts and plasma mixed gas;

[0050] (7) Purge the cavity with 8000 sccm N2. After purging, pressurize to 10 mtor and repeat 1-5 times to empty the cavity of residual plasma and side reactants.

[0051] (8) Remove the cleaned graphite boat from the cavity.

[0052] Comparative Example 1

[0053] Comparative Example 1 and Example 1 used the exact same graphite boat to be cleaned.

[0054] The difference between Comparative Example 1 and Example 1 is as follows:

[0055] (5) 900 sccm NF3 is introduced into the cleaning chamber, the reaction temperature is 350℃, the radio frequency power is 6500W, the duty cycle is 1:2, and the cleaning time is 8000s, so as to achieve efficient cleaning of silicon nitride film and silicon oxynitride film on the surface of graphite boat.

[0056] The cleaning results of Example 1 and Comparative Example 1 show that, under the same conditions of temperature, RF power and duty cycle, the NF3 consumption of Example 1 is reduced by 17% compared to Comparative Example 1.

[0057] Comparative Example 2

[0058] Comparative Example 2 used the exact same graphite boat to be cleaned as Example 1.

[0059] The difference between Comparative Example 2 and Example 1 is as follows:

[0060] (5) 750 sccm NF3 is introduced into the cleaning chamber, the reaction temperature is 350℃, the radio frequency power is 6500W, the duty cycle is 1:2, and the cleaning time is 9600s, so as to achieve efficient cleaning of silicon nitride film and silicon oxynitride film on the surface of graphite boat.

[0061] The cleaning results of Example 1 and Comparative Example 2 show that, under the same NF3 flow rate, temperature, RF power, and duty cycle, the cleaning time of Example 1 was reduced by 17% compared to Comparative Example 2.

[0062] Example 2

[0063] A mixed gas of NF3, CO2, and Ar was used to clean the silicon oxide film and silicon-based film on the surface of the graphite boat.

[0064] (1) The graphite boat to be cleaned, and the depth of the electrode rod inserted into the graphite boat is adjusted;

[0065] (2) Set the cleaning chamber temperature to 500℃, and heat the chamber until it stabilizes at that temperature;

[0066] (3) Purge with 8000 sccm N2 for 60 seconds, then reduce the chamber pressure to 50 mtor to remove air from the chamber.

[0067] (4) Evacuate the cleaning chamber to a vacuum pressure of 2000 mtor;

[0068] (5) Introduce 750 sccm NF3, 560 sccm CO2, and 2500 sccm Ar into the cleaning chamber. The reaction temperature is 350℃, the radio frequency power is 7000W, the duty cycle is 1:2, and the cleaning time is 8200s to achieve the cleaning of the silicon oxide film and silicon-based film on the surface of the graphite boat.

[0069] (6) Evacuate the cleaning chamber to 10 mtor to remove excess byproducts and plasma mixed gas;

[0070] (7) Purge the cavity with 8000 sccm N2. After purging, pressurize to 10 mtor and repeat 1-5 times to empty the cavity of residual plasma and side reactants.

[0071] (8) Remove the cleaned graphite boat from the cavity.

[0072] Comparative Example 3

[0073] Comparative Example 3 and Example 2 used the exact same graphite boat to be cleaned.

[0074] The difference between Comparative Example 3 and Example 2 is as follows:

[0075] (5) Introduce 950sccmNF3 into the cleaning chamber, with a reaction temperature of 350℃, a radio frequency power of 7000W, a duty cycle of 1:2, and a cleaning time of 8200s to achieve the cleaning of the silicon oxide film and silicon-based film on the surface of the graphite boat.

[0076] The cleaning results of Example 2 and Comparative Example 3 show that, under the same conditions of temperature, RF power, duty cycle and cleaning time, the NF3 consumption of Example 2 was reduced by 21% compared to Comparative Example 3.

[0077] Comparative Example 4

[0078] Comparative Example 4 and Example 2 used the exact same graphite boat to be cleaned.

[0079] The difference between Comparative Example 4 and Example 2 is as follows:

[0080] (5) Introduce 750sccmNF3 into the cleaning chamber, with a reaction temperature of 350℃, a radio frequency power of 7000W, a duty cycle of 1:2, and a cleaning time of 9900s to achieve the cleaning of the silicon oxide film and silicon-based film on the surface of the graphite boat.

[0081] The cleaning results of Example 2 and Comparative Example 4 show that, under the same NF3 flow rate, temperature, RF power, and duty cycle, the cleaning time of Example 2 was reduced by 17% compared to Comparative Example 4.

[0082] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0083] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A dry cleaning method for a graphite boat, wherein the coating on the surface of the graphite boat comprises at least one of a silicon-based thin film, a silicon oxide thin film, a silicon nitride thin film, and a silicon oxynitride thin film, characterized in that, include: A cleaning gas is introduced into the cleaning chamber to perform radio frequency dissociation on the cleaning gas in order to etch and clean the coating on the surface of the graphite boat. The cleaning gas includes CO2, O2, and NF3.

2. The dry cleaning method for graphite boats according to claim 1, characterized in that, The cleaning gas also includes an inert gas.

3. The dry cleaning method for graphite boats according to claim 1, characterized in that, When the coating on the surface of the graphite boat is a silicon-based thin film and / or a silicon oxide thin film, the cleaning gas includes NF3 and CO2; When the coating on the surface of the graphite boat is a silicon nitride thin film and / or a silicon oxynitride thin film, the cleaning gas includes NF3 and O2.

4. The dry cleaning method for graphite boats according to claim 1, characterized in that, NF3 and CO2 are introduced into the cleaning chamber for radiofrequency dissociation cleaning. The volumetric flow rate of NF3 is 500 sccm to 2000 sccm, and the volumetric flow rate of CO2 is 300 sccm to 2000 sccm. NF3 and O2 are introduced into the cleaning chamber for radio frequency dissociation cleaning. The volumetric flow rate of NF3 is 500 sccm to 2000 sccm, and the volumetric flow rate of CO2 is 400 sccm to 2000 sccm.

5. The dry cleaning method for graphite boats according to claim 4, characterized in that, The temperature of the cleaning chamber is 100℃~400℃, and the power of the radio frequency is 4000W~8000W.

6. The dry cleaning method for graphite boats according to claim 2, characterized in that, The volumetric flow rate of the inert gas is no more than 3000 sccm.

7. The dry cleaning method for graphite boats according to claim 5, characterized in that, The radio frequency dissociation process includes: (1) The cleaning gas is introduced into the cleaning chamber for the first radio frequency dissociation cleaning in order to remove the coating with a thickness of 60% to 80% on the graphite boat. (2) Reduce the radio frequency power to perform a second radio frequency dissociation cleaning in order to remove the remaining 20% ​​to 40% thickness of the coating on the graphite boat.

8. The dry cleaning method for graphite boats according to claim 7, characterized in that, The power of the second radio frequency deionization is 100W to 1000W less than the power of the first radio frequency deionization.

9. The dry cleaning method for graphite boats according to any one of claims 1-8, characterized in that, Also includes: Before introducing the cleaning gas into the cleaning chamber, the cleaning chamber is evacuated for the first time. After the coating on the surface of the graphite boat is etched and cleaned, the cleaning chamber is evacuated a second time to remove the reaction waste gas.

10. The dry cleaning method for graphite boats according to claim 9, characterized in that, After the first vacuuming, the vacuum pressure of the cleaning chamber is 1000 mtor to 3000 mtor; After the second vacuuming, the vacuum pressure of the cleaning chamber is 0 mtor to 20 mtor.

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